British
Geological
Survey
EARTHWISE
Earthwise is
the official
magazine of
the British
Geological
Survey.
Earthwise is
published
twice a year
and describes
the role of the
BGS in
supporting
wealth
creation and
the quality of
life, through
earth science.
Geohazards
Issue 14
I am delighted to introduce this issue of Earthwise,
which serves to recognise the contribution the British
Geological Survey (BGS) makes to the study of geohazards and their effects. The term 'geohazard' covers
a wide range of events and processes. This issue of
Earthwise focuses on four different categories of
geohazard at global, regional and local scales, in the
UK and overseas, and emphasises the need for all
processes to be fully understood so that the effects
can be abated in the future.
In recent times the BGS has been involved in the
study of the catastrophic effects of natural
phenomena, most notably frequent volcanic activity
on Montserrat. The keynote article, contributed by
Dr P Dunkley, BGS, addresses the global issue of the
problems and dangers relating to volcanic activity.
This article emphasises the need for non-geoscientists, such as planners and politicians, to be more aware
of a wide range of geohazards, through increased consultation, in order that the risks are more fully
understood and incorporated into land-use planning and policy.
As well as global issues, other categories of geohazard covered are ground stability, offshore hazards and
issues relating to health and urban areas. The BGS holds a National Landslides Database, containing the
details of over 8000 slides. Landslides and ground motion amplification present major hazards in countries
such as Barbados and Costa Rica, which are both popular holiday destinations. It is vital therefore that tourist
developments are sited outside these danger areas. Salt mining can also have a detrimental effect on ground
stability since the mineral is highly soluble, a significant problem in Cheshire. The investigation of subsidence due to the solution of salt through salt mining, and other factors such as the shrinkage and swelling of
clays, must be taken into consideration during the planning of new developments.
In the section on offshore hazards, it is demonstrated how the combination of datasets relating to the
development of coastal lowlands in the UK can help to predict future sea-level rise. Coastal erosion on a
large scale has been observed at Beachy Head, a well-known beauty spot on the south coast. The BGS
recently carried out an engineering geological survey in order to assess the long-term stability of the
cliffs there. On a global scale, highly destructive tsunamis, or mountainous waves, are known to be
affected by the sea bed morphology which can serve to focus waves. Hence the interpretation of offshore
data can assist in determining their cause.
Geohazards can have substantial effects on urban life and health. A recent geophysical survey, performed
by the BGS, helped unearth a concealed mineshaft at the Hopewell Pit near Newcastle, which had closed
during the early nineteenth century. Danger of subsidence was therefore abated. Geophagia, the practice
of eating earth, is currently being investigated by BGS geochemists. This ancient method of obtaining
extra vitamins and minerals dates back to the time of Aristotle, and might be considered as the forerunner
to the modern vitamin pill! A further health issue is that of air quality and the need for accurate detection
due to the increase of illnesses such as asthma, especially in young children.
This issue of Earthwise emphasises the need for the understanding of natural processes, of their causes
and effects, and subsequent dangers. The visual presentation of geohazard datasets collected during the
monitoring of natural phenomena can be used to inform non-geoscientists, such as planners and politicians, of the potential risks and effects of such geohazards. It is of the utmost importance that individuals
understand this information so that catastrophes can be avoided in the future. The BGS prides itself on
the depth and breadth of the geoscience expertise it holds in this increasingly important area, and will
continue to educate and inform the non-geoscientific community of the likely dangers so they can be
avoided with more confidence in the future.
David A Falvey, PhD
Director
Contents
Global
geohazards
Volcanic hazards
Earthquakes
Tsunami
Magnetic storms
Gas seepage
Building subsidence
Peter Dunkley
Roger Musson
David Tappin
Toby Clark & David Beamish
Nigel Smith
Peter Hobbs, Martin Culshaw &
Alan Forster
11
Alan Forster
Landslides in Hong Kong
12
Simon Kemp & Dick Merriman
Subsidence in the Chalk
13
Peter Jackson, David Gunn, Robert Flint,
Michael Ben & David Howes
Salt subsidence
14
Anthony Cooper
Collapsing loess soils
15
Kevin Northmore, Ian Jefferson,
Ian Smalley & Caroline Tye
Fault reactivation
16
Alan Forster
Landslides and tourist development
17
Chris Evans
Cliff stability and coastal landslides
18 – 19
Ground stability
Inland landslides in Britain
Coastal and
offshore
Urban and health
4–5
6
7
8
9
10
Alan Forster, Peter Hobbs & Robert Flint
Estuarine contamination
20
John Ridgway, Steve Rowlatt
& Peter Jones
Relative sea-level rise
21
David Brew & Russell Arthurton
The Western Frontiers Association
22
David Long
Urban geohazards
23
Andrew Howard
Earthquake-generated ground motion amplification
24
Peter Jackson, David Gunn,
Martin Culshaw & Alan Forster
Tsunamis and the urban environment
25
David Gunn, Martin Culshaw,
Alan Forster & Peter Jackson
Mines and bombs
26
David Beamish & Steve Shedlock
A diet of dirt
27
Barry Smith
Airborne particulates
28
Vicky Hards
Montserrat ash
29
Dick Nicholson, Vicky Hards
& Barbara Vickers
The legacy of mining
30
Steve Shedlock, David Beamish
& Lorraine Williams
Cover illustration: Ash cloud from the eruption of
6th August 1997 Soufriere Hills, Montserrat.
Photo: G E Norton, British Geological Survey © NERC, 1997. The
image is a product of the DFID programme of work carried out in
Montserrat by the BGS.
Newsline
31 – 34
Global geohazards
Global geohazards
Volcanic hazards
Hazard, vulnerability
and risk assesment
by Peter Dunkley, Keyworth
I
Volcanic eruptions produce a number of
different hazards, including lavas, pyroclastic falls, pyroclastic flows, pyroclastic surges, lateral blasts, debris
avalanches, volcanogenic tsunamis,
mudflows and floods and gases. A basic
premiss of volcanic hazard assessment is
that hazard impact is generally related to
the size of the eruption and proximity to
the volcano. There are exceptions to this
rule, as exemplified by a number of
snow-capped Andean volcanoes that
produce catastrophic floods and
mudflows which have on several
occasions devastated distant urban areas.
Such a catastrophe befell the Colombian
city of Amaro in 1985, where 24,000
people were killed by mudflows
generated by a relatively small eruption
which partly melted the summit ice cap
of Nevado del Ruiz, some 50 km from
the city. Whilst such dramatic volcanic
disasters are well-publicised, even relatively benign activity such as prolonged
periods of degassing and light ashing can
have substantial adverse effects. Studies
undertaken by the BGS of Volcán Irazú
near the Costa Rican capital of San José
indicate that a prolonged but relatively
small eruption in 1963–65 caused health
problems, and resulted in a marked
reduction in GDP despite increased
prices for the country’s principle export
commodities.
As with other natural hazards, the level of
volcanic risk may be reduced by disaster
prevention, preparedness and emergency
response measures. Hazard assessment
underpins all of these activities and is
fundamental to sound land-use planning,
which offers the most effective means of
reducing volcanic risk in the longer term.
As part of the United Kingdom’s contribution to the United Nation’s
International Decade for Natural Disaster
Reduction (IDNDR), the BGS was commissioned by the Department for
International Development (DFID) to
investigate the role of volcanic hazard
maps in development planning and to
develop a methodology for the rapid production of first-pass hazard maps.
Experience from past volcanic crises and
disasters has shown that problems exist in
the uptake and utilisation of volcanic
hazard information by civil authorities. To
improve this interface non-geoscientists
need to be involved in the process of
hazard assessment and should be
educated in the nature and effects of the
hazards. As described above, better visual
presentation methods for hazard maps are
also advantageous, although probably the
most effective means of communicating
the potential impact of volcanic eruptions
Andrew McDonald © BGS, NERC
t is estimated that more than 500
million people, mostly within the
developing world, live under the
threat of hazards posed by
volcanoes. The potential therefore exists
for major loss of life and damage to
property and infrastructure, especially
where large urban areas occur in
proximity to dangerous volcanoes. As
population pressures intensify,
hazardous areas are likely to become
increasingly developed, so raising the
level of risk.
Volcanic hazard assessments are
generally based upon the assumption
that the future activity of a volcano will
be similar to past activity, in terms of
style, size and frequency of eruption.
Such information on past activity may
be obtained from historical records, and
from the examination, interpretation and
dating of ancient deposits which permit
the elucidation of a volcano's evolution.
Reconnaissance survey methods,
including photogeological interpretation
and satellite image analysis have been
applied by the BGS to a number of
volcanoes in Chile and Costa Rica and
have been shown to be effective for the
rapid production of first-pass volcanic
hazard maps. Combined with GIS-based
digital techniques, such hazard maps
may be presented in forms more easily
visualised and understood by non-geoscientists involved in the downstream
activities of volcanic risk reduction.
Example of a hazard map of Volcán Villarrica, Chile, draped over a perspective view of the
volcano.
4
Global geohazards
Global geohazards
Left: Lahar hazard zones for Volcán
Villarrica, presented on a shaded relief map
to aid visual interpretation. The probability
of impact varies from high (red) to low
(yellow). Grey areas are not affected by the
hazard.
Below: Landsat image of Volcán Villarrica
and surrounding area. Lakes appear black
and snow red. The white streak over the
summit is due to sensor overload by heat
from the lava-filled crater.
Andrew McDonald © BGS, NERC
is to incorporate information within risk
maps. These offer distinct advantages
over hazard maps, by providing more
meaningful or tangible indications of the
losses that may arise as a consequence of
volcanic activity. Such losses may be
expressed in economic terms or as human
casualties, and are useful in demonstrating
the need for, and the cost benefits of,
hazard mitigation, including long-term
planning, volcano monitoring, and civil
defence measures.
“... it is estimated that 500
million people, mostly within the
developing world, live under the
threat posed by volcanoes ...”
In order to quantify risk, it is necessary to
undertake vulnerability assessments.
Vulnerability may be defined as the
degree of loss to a given element or
group of elements, such as people,
property or economic activity, resulting
from the occurrence of a hazard of a
given magnitude, and expressed on a
scale from 0 (no damage) to 1 (total loss).
Vulnerability may be assessed empirically or analytically. The empirical
approach assesses vulnerability by
examining the adverse impacts of
hazardous volcanic phenomena during
previous disasters. The analytical
approach is particularly applicable to
assessing the built environment, by
looking at the materials and designs used
in construction and calculating the effects
and failure rates of structures in response
to physical conditions likely to be experienced during eruptions. Both of these
approaches have been used to assess the
vulnerability of buildings in the BGS
study of Volcán Irazú and the methodologies were later applied to estimate the
risk to buildings during the recent
volcanic emergency on Montserrat.
Volcanic risk for a given hazard zone
and specified period of time may be
estimated as:
vulnerability 3 hazard probability 3 value
of the element at risk.
Value may be expressed either as
numbers of people or in monetary terms
in the case of constructions or economic
activity. In theory this is a relatively
simple process, although in practice it
5
involves a great deal of laborious data
gathering. As a result, very few volcanic
risk assessments have been undertaken,
and those that have been attempted have
been restricted to the risks imposed by
selected volcanic hazards on specific
elements, such as estimates of human
casualties or numbers of collapsed roofs
due to ash-loading. Nevertheless, specific
risk assessments of such key elements are
sufficient to act as indices which demonstrate to planners and politicians in
understandable terms the impacts that
might be expected and how these may be
mitigated within the framework of landuse planning. Whilst it has been demonstrated that the methods exist for
producing effective and cost-beneficial
hazard and risk assessments, the greatest
challenge remains to convince politicians
and administrators that such assessments
are worth putting into action in the first
place.
Global geohazards
© Dr Roger Hutchison, courtesy NOAA,
US National Geophysical Data Centre.
Global geohazards
Earthquakes
Protection through engineering,
planning and insurance
by Roger Musson, Edinburgh
Concrete frame office building completely
destroyed in Kobe earthquake of 1995.
f all the natural phenomena
capable of inflicting disasters
upon human communities,
earthquakes are perhaps the
most frightening, the most unpredictable,
and the most expensive. The 1994
Northridge earthquake in California caused
insured losses of over $10 thousand
million; the total losses were significantly
higher. Total losses from the Kobe earthquake in Japan the following year were
around $150 thousand million. Yet neither
of these were great earthquakes. Both had
magnitudes of just under 7. From this one
should learn that even moderate earthquakes can cause very high losses if they
score a direct hit on a major city, especially
cities that are unprepared because they are
mistakenly believed not to be at risk.
earthquakes. Many scientists are now
discussing the idea that such predictions
may be impossible because of the
chaotic nature of earthquakes. Also, the
societal impact of earthquake prediction
is now being questioned. For example: if
earthquakes were to become predictable,
could they be insured against?
O
Increasingly, it is being seen that the key
to protecting against earthquakes is
threefold: engineering to strengthen
buildings, planning to minimise casualties, and insurance to cover the cost. All
these approaches require advice from
the seismological community in order to
strike the right balance. The engineer
needs to know what sort of shaking to
design against; the planner needs to
know what sort of effects to prepare for,
and the insurer needs to know how to
cost the expected risk correctly.
At one time it was thought that earthquake prediction would solve this
problem. This now looks increasingly
unlikely. After decades of research there
still is no prospect of reliably predicting
25
26
27
28
29
There are three basic types of information that are relevant:
30
31
Seismic Risk Curves by Building Type for a site in Turkey
41
1
0.1
Annual Probability
40
39
38
0.01
0.001
■
Seismicity — the raw information
about how frequently earthquakes
affect a place;
■
Seismic hazard — the probability
that a certain strength of shaking will
occur;
■
Seismic risk — the probability that a
certain amount of loss will occur.
Seismicity information is useful in
making preliminary assessments about
whether earthquakes are a serious threat
in any particular place. Then seismic
hazard information is used by engineers
to derive design parameters for structures, while insurers and planners need
seismic risk data to assess the likelihood
of existing buildings being damaged.
The BGS has been involved in research
into seismicity and seismic hazard since
the mid 1970s. It is becoming increasingly involved in seismic risk work as
well, especially in developing new
approaches to tackling this important
subject. By looking at past data, one can
estimate the way damage to particular
types of buildings is distributed as a
function of earthquake magnitude and
distance from the focus of the earthquake.
One can then apply simulation techniques
to estimate the probability of damage
from future earthquakes. Software to
perform this analysis is now being
licensed by the BGS to reinsurance firms;
a way of applying the scientific
knowledge of seismologists to the
practical goals of the insurance industry.
0.0001
37
0.00001
0
10 20
30
Poor Masonry
36
Masonry
Reinforced Concrete
25
26
27
28
29
40
50
% Loss
60
70
Antiseismic design
6
80
90 100
Seismic risk: these curves show the probability
of different amounts of loss to buildings of
different degrees of vulnerability for a town in
Western Turkey. The background map shows
the seismicity of the area.
Global geohazaards
Global geohazards
Tsunami
The PNG event of July 1998
sunami, often inaccurately
termed tidal waves, are a surprisingly common phenomena.
Since 1990 there have been 82
tsunami reported globally, with ten taking
more than 4000 lives. The devastating
tsunami that struck the northern coast of
Papua New Guinea (PNG) on 17th July
1998 claimed 2200 lives as mountainous
waves up to 15 metres high completely
destroyed three villages and severely
damaged four others. With such a loss of
life there was an immediate response
from the scientific community. For the
first time there was a comprehensive
investigation that included onland study,
offshore sea bed imaging, geological
interpretation and computer simulation.
Two offshore surveys, acquiring sea bed
bathymetry and visual images were
carried out very soon after the event.
T
Until recently, tsunami studies had mainly
focused on transoceanic tsunami where the
source is far distant and warning times of
up to 24 hours are practicable. However,
David Tappin © BGS, NERC
by David Tappin, Keyworth
there has been an increasing recognition
that locally sourced tsunami, such as the
PNG event may be as frequent and as devastating as these ‘far-field’ events. Warning
times for tsunami generated locally may be
only minutes, thus different mitigation
strategies have to be developed.
Most tsunami are the direct result of
seafloor displacements caused by major
earthquakes. However, for the PNG
event the earthquake magnitude (~7)
was too low and the earthquake not of
the right type to produce such large
waves. Initial computer simulations of a
fault source also failed to recreate the
wave heights and distribution along the
coast. A major constraint on the simulations was the lack of detailed seabed
bathymetry data — it is well known that
seabed morphology has a critical
influence on focusing the tsunami wave.
An alternative tsunami source
mechanism considered was an offshore
sediment slump created by the shaking
effect of the earthquake.
Map of the offshore survey
area. Bathymetry is shown
offshore. Star is earthquake epicentre. Numbers
are ROV dive locations.
R = Subsided reef. Red
dots are the communities
most devastated by the
tsunami. Inset map shows
survey area with the main
plate tectonic segments.
Upper: the maximum water level surface of a
tsunami generated from the sediment slump.
Lower: a comparison of measured water
levels on the coast (circles) with computed
water levels (line) at the 10 m contour derived
from a tsunami originating from the location
of the sediment slump. (Note: The difference
between the measured and computed water
levels is due to an overly conservative
estimate of the initial slump shape and motion.
Water depths between the coast and 200 m are
interpolated.)
With the acquisition of offshore data, discrimination was made possible between a
coseismic and a sediment slump tsunami
source. 25 kilometres offshore of the most
affected area a sea bed feature was identified that closely resembles a slump. Visual
evidence (fissures, breccias, talus slopes
and headwall collapse) from a Remotely
Operated Vehicle (ROV) indicates recent
movement of the sea bed in this area. With
the new detailed bathymetry, improved
computer simulations now reflect the true
wave distribution along the coast. Verbal
evidence from survivors on the relative
timing between the felt earthquake,
thought to have triggered the slump, and
the arrival of the tsunami waves at the
coast indicates that a slump is the most
likely cause of the event. On the basis of
these new data, mitigation strategies that
will protect life and property are being
developed.
David Tappin © BGS, NERC
The figures are based upon Tappin et.al., in press.
Offshore surveys identify slump as likely cause of
devastating Papua New Guinea Tsunami 1998. Eos
Transactions. AGU.
7
Global geohazards
Global geohazards
Magnetic storms
When the Sun threatens to
turn out the lights
by Toby Clark, Edinburgh & David Beamish, Keyworth
Magnetic storms are periods when the geomagnetic field exhibits large fluctuations
on timescales of minutes to hours. A
magnetic storm starts with an eruption on
the Sun sending out a plasma cloud which
takes between one and three days to reach
Earth. When it arrives near Earth, electric
currents are generated in the upper atmosphere resulting in variations in the surface
magnetic field. These events are
commonly associated with auroral
displays. The occurrence of magnetic
storms roughly follows the 11-year sunspot
cycle, with fewest storms during sunspot
minima, and most storms in the three years
following sunspot maxima.
The hazard to power transmission stems
from geomagnetically induced currents
(GICs) which are induced in the Earth and
in the grid by the varying geomagnetic
field. When flowing through transformers
at each end of the transmission line,
intense GICs can cause half-cycle saturation, leading to overheating and harmonic
generation. Additionally, transformer protection cut-outs may be triggered in many
Usually, high-latitude regions under the
auroral zone experience the most intense
magnetic storms. However, during severe
magnetic storms the auroral belt moves
equatorwards over the British Isles, so the
GIC risk to the power grid is of concern
to the UK electricity industry.
The UK grid is operated by the National
Grid Company (NGC), Scottish Power
and Scottish Hydro-Electric. These
companies are preparing themselves for
the next period of maximum magnetic
activity due in 2000–2003. The BGS has
carried out two GIC related studies for the
NGC. One study used 15 years of recordings of magnetic variations from the three
BGS observatories in the UK to provide
statistics of storms resulting in noticeable
GIC effects in the grid. This will help
David Beamish © BGS, NERC
A
lines simultaneously, leading to the rest of
the grid becoming overloaded.
An additional service developed by the
BGS in recent years for customers in the
space and oil industries is monitoring
magnetic activity in near real-time,
combined with prediction of magnetic
activity up to three days ahead by neural
networks using observations of geomagnetic and solar activity. This can be
useful to grid operators for putting contingency plans into action during times
of increased GIC risk.
The surface electric field induced by geomagnetic variations over the British Isles,
computed using a 3-D geological model.
Paul Tod © BGS, NERC
t 02:45 EST on 14 March
1989 the entire electricity
power grid in Quebec was
blacked out, leaving six
million people without electricity for a
number of hours. This major disruption
resulted from a natural geophysical phenomenon called a magnetic storm. It
was known that magnetic storms may
have detrimental effects on electricity
transmission systems, but until this
event no catastrophic failures had
occurred, so the problem was more of
engineering interest than of operational
concern. Despite accurate prediction of
the storm, which turned out to be one of
the most severe on record, the operating
company had no adequate procedures
for dealing with the situation.
assess long term cumulative damage to
transformers from GICs. The second
study developed a 3-D model of earth
conductivity around the British Isles to a
depth of 1000 km, which is used by the
NGC to compute the surface electric field
which drives GICs in the grid.
Magnetic storms may have detrimental effects on electricity transmission systems.
8
Ground stability
Ground stability
Gas seepage
ERC
Shrines, curiosities
and hazards
he gases emitted from seeps and
springs are methane (CH4),
nitrogen (N2), hydrogen
sulphide (H2S) and carbon
dioxide (CO2 ). Hydrogen (H2) is associated with ultrabasic and gypsum rocks.
The sources of the gases are bacterial,
thermal (burial of sediments) and
volcanic (e.g. the CO2 disaster at Lake
Nyos, Cameroon) and a mixture is often
present (e.g. Lake Kivu, Zaire).
T
Methane (also known as marsh gas),
carbon dioxide and nitrogen are produced
by bacterial action, most commonly manifested by will o’ the wisp from stagnant
lakes and swamps, with accumulation
rates of 75–100 cubic feet per day (cfd)
per acre attained in the tropics.
Exceptionally, if trapping conditions are
right, sufficient quantities form gasfields
(e.g. Kanto region of Japan). Seeps from
landfills have similar compositions.
Gas caps to oilfields, known as associated gas, often leak to the surface,
guiding explorers to fields; larger
amounts of non-associated gas are
produced by burial of gas-prone
sediments (e.g. the Coal Measures of
Europe). In some places (Poota Valley,
Baku; Yenang Daung, Burma; Lizard
Spring, Trinidad and Turner’s Hall,
Barbados) gas has escaped for years and
even millenniums. Fire worship has
taken place at temples near Baku for
2500 years and the Hindus erected a
shrine over a gas seep at Chittagong,
Bangladesh. Many of these examples
are associated with mud volcanoes,
which erupt periodically, ejecting rocks,
mud, gas, oil and water. The Dashgil
mud volcano, Azerbaijan emitted about
4000 cfd of gas from its 45 active cones.
coal mines, where coals contain Coalbed
Methane. Methane (also known as
firedamp) in coal mines has caused
many fatal explosions. Base metal mines
have also encountered gas, for example
in the Carboniferous Limestone
reservoir (Derbyshire lead mines),
overlain by hydrocarbon source rocks
(Edale Shales). In 1984 in Lancashire at
the Abbeystead valve house of the
Lune–Wyre water tunnel, a fatal
explosion was caused by methane
migrating from Millstone Grit strata.
A methane gas seep, which reached the
surface near Broseley in Shropshire, woke
residents in 1711. It was developed as a
tourist attraction and, when it ceased,
exploration was conducted for a replacement, eventually proving successful in
1745. From descriptions, the observers
were unsure of the cause of these ‘burning
(or boiling) wells’. The occurrences may
have been natural surface emanations or
perhaps were triggered by early coal explo-
© BG
S arch
ives, N
by Nigel Smith, Keyworth
Passage from Philosophical Transactions of
the Royal Society 1711, volume 28, 475–476
on the Broseley well.
ration; mining operations have disturbed
natural migration pathways and methane is
sometimes deliberately drained (e.g.
Cardowan, and Wolstanton collieries) to
prevent accidents. Closure of collieries will
initiate further changes to these pathways.
Carbon dioxide has caused deaths,
including that of a Geological Survey
officer in 1945, who descended a newlysunk, fifty-foot shaft at Seaton, Cumbria.
At a time of low barometric pressure
carbon dioxide accumulated at the
bottom of the shaft, but no gas occurred
in the shaft before or after the accident. In
parts of East Anglia, a number of shallow
wells drilled in the 19th century encountered carbon dioxide in Tertiary strata.
This caused inconvenience, putting out
workers’ candles, requiring bellows to be
deployed and sometimes reached the
surface, killing workers and chickens.
Many hydrogen sulphide springs were
once fashionable medicinal spas. There
are two main areas in the UK: springs
issue along faults, anticlines and the
margins of the Dinantian sub-basins of
the Pennine Basin (e.g. at Craven and
Widmerpool) and hydrogen sulphide is
found in wells drilled in the Lower Lias
of central England.
Dashgil mud volcano eruption.
The photograph of Dashgil Mud Volcano is reproduced from figure 269, page 134 of 'Mud
Volcanoes of the Azerbaijan SSR: an Atlas'
Jakubov, A. A., Ali-Zade, A. A. & Zeinalov, M. M.
Publishing House of the Academy of Sciences of
the Azerbaijan SSR. Baku, 1971.
British examples, in comparison, are
small and short-lived. Gases are most
often encountered in mines, particularly
9
Ground stability
Ground stability
Building subsidence
A seasonal hazard
materials and a means by which they
can be identified and quantified. There is
also close collaboration between the
BGS and the National House Building
Council who deal nationally with the
consequences of clay shrink/swell to
individual homes covered by their
guarantee scheme.
by Peter Hobbs, Martin Culshaw & Alan Forster, Keyworth
uilding subsidence is a
perennial problem for many
home-owners and builders
alike. Every year hundreds of
millions of pounds are spent in remedial
works and compensation, and properties
are devalued, sometimes unnecessarily,
as a direct result of subsidence. The
causes of subsidence include the
shrinkage and swelling of clay, mining,
dissolution, and metastability. However,
of these the most significant in terms of
extent, frequency and total cost is clay
shrink/swell. In Britain, the most vulnerable areas are in the south-east and
Midlands of England where younger
geological formations, such as the
London Clay and the Gault clay, predominate. Not all clay formations have
the same susceptibility to shrink/swell.
This is largely dependent on the particular mineralogy of the clay. This in turn
is dependent on the original rock
material from which the clay minerals
were formed, and the age and post-depositional history of the clay formation.
B
parameter is seldom determined because
the test requires the use of mercury, a
hazardous substance. The ‘shrinkage
limit’ defines the water content below
which substantial shrinkage ceases. The
lower the value of the shrinkage limit
the greater the range of water contents
over which a clay is able to shrink. The
test also defines an important part of the
shrinkage vs. water content curve, characteristic of the clay. Also, the BGS is
contributing to a new research
programme using satellite-borne radar
interferometry (InSAR) to measure the
seasonal change in ground level of the
London Clay outcrop attributable to clay
shrink/swell. These projects are at
opposite ends of the research scale, but
each will contribute to a better understanding of shrink/swell susceptible
“... every year hundreds of
millions of pounds are spent in
remedial works and compensation, and properties are
devalued, sometimes
unnecessarily, as a direct
result of subsidence ...”
The opposite of shrinkage is swelling,
that is, an increase in the volume of a
clay due to the take up of water.
Swelling might become a problem
following flooding after a long dry
period, or as a result of a leaking water
pipe or sewer. The swelling process
tends to affect the same clay formations
as shrinkage, but the effects on a
building are different, though equally
damaging.
Research is under way at the BGS into
new methods of measuring ‘shrinkage
limit’ in the laboratory. Currently, this
Martin Culshaw © BGS, NERC
Whilst the underlying causes of clay
shrink/swell are the respective loss or
gain of water from the soil and the susceptibility of the clay minerals, the
actual ground deformations beneath
buildings are also a function of rainfall,
temperature, drainage, foundation type
and depth, building materials, nearby
vegetation, and soil structure. Clay
shrink/swell can be exacerbated by the
addition or removal of trees and by
leaking pipes. Specialist structural
surveyors are able to calculate the
precise triggering factors of shrinkage,
or swelling, or to identify causes other
than shrink/swell, from the type and disposition of cracking within a building’s
floors and walls.
Diagonal crack in new terrace due to swelling of London Clay along former hedge-line, Vange,
south-west Essex.
10
Ground stability
Ground stability
Inland landslides
in Britain
Alan Forster © BGS, NERC
Building a database to
monitor unstable ground
by Alan Forster, Keyworth
ritain does not suffer from landslides of the magnitude experienced in actively growing mountainous regions such as the South
American Andes, where landslides have
devastated large areas of land with great
loss of life. However, we do have many
landslides in Britain (more than 10 000
are known), and some are very large and
spectacular such as those in the South
Wales Coalfield and Mam Tor.
Fortunately most are also ancient,
dormant and enhance our scenery rather
than threaten property and lives. A recent
landslide at the Coombs near Ainthorpe in
North Yorkshire provides good illustrations of the sort of features that are
formed during landslide activity and
demonstrates the severe damage to roads
that they can cause.
Alan Forster © BGS, NERC
B
First time landslide activity occurs from
time to time through natural causes,
such as unusually heavy rainfall and the
weakening of rock as it weathers. More
often, movement is a reactivation of a
dormant slide that may have moved
originally in the wetter conditions at the
end of the last ice age. Landslides may
also be triggered artificially by illadvised land use, such as excavations at
the foot of slopes, saturating slopes by
the ill-considered disposal of surface
water and loading slopes by dumping
material on them. The movements
started by such actions are often
extremely difficult and expensive to
stabilise, but could usually be avoided
by taking expert advice at an early stage
of project planning. The BGS holds a
National Landslide Database that
contains reference to over 8000 slides
within England and Wales but the
database is the product of a data search
and only slides that have been
recorded in the literature or on the
maps produced by the BGS are
included. It is known that many
more landslides are present in
Britain that could be recognised, mapped and described
by a walk-over survey.
Therefore, when considering
the landslide potential of a
site, it is as important to
recognise the conditions that
Severe cracking of a road
surface due to landsliding at
Coombs near Ainthorpe, North
Yorkshire.
11
Very large toppling failure in Pennant
Sandstone at the head of the Rhondda
Valley, South Wales.
predispose a slope to landsliding, such
as slope angle, geology and groundwater, as it is to consider existing records
of known landslides.
“... it is known that many more
landslides are present in Britain
that could be recognised,
mapped and described by a
walk-over survey ...”
Every year new slides take place and
dormant slides are reactivated. The BGS
updates its landslide records as time and
resources allow but can only do so
where slides are sufficiently large to be
newsworthy, or when notification is
received from the many contacts that are
maintained with other geologists and
engineers working in Britain. Therefore,
the BGS would welcome notification of
the occurrence of new landslides or the
reactivation of existing ones.
Information regarding landslides should
be addressed to Prof. Martin Culshaw,
Coastal and Engineering Geology
Group, British Geological Survey,
Keyworth, Nottingham, NG12 5GG or
E-mail [email protected].
Ground stability
Ground stability
Landslides in
Hong Kong
The role of clay minerals
by Simon Kemp & Dick Merriman, Keyworth
n August 1995, following the torrential rainstorms of Typhoon Helen, a
series of more than 70 landslides
were triggered in Hong Kong Island,
some causing fatalities, injuries and
damage to property.
I
The Geotechnical Engineering Office
(GEO), Hong Kong undertook forensic
investigations at some of the major sites
and as part of this programme, the BGS
were commissioned to carry out a series
of integrated mineralogical and microtextural studies of samples from the
landslides.
Two kaolin-group minerals, kaolinite
and halloysite were found in the
saprolite. Both minerals have similar
chemistries and a relatively simple 1:1
layer structure but halloysite possesses
an additional layer of poorly bound
water. It is the presence of this layer of
water which is, in part, responsible for
the more plastic engineering behaviour
of halloysite-bearing rocks. The results
of X-ray diffraction analysis of
formamide-treated samples indicate that
the proportion of halloysite was greater
in samples of kaolin-filled joints. But
how do halloysite and kaolinite relate to
one another?
In situ microtextural relationships were
observed in ‘field-moist’ samples using
cryo-scanning electron microscopy
(SEM), which minimises damage to
delicate clay mineral crystals during
imaging. Kaolinite occurs as relatively
coarse-grained ‘books’ of hexagonal
plates, often forming vermicular stacks.
In contrast, halloysite occurs as fibres
replacing the kaolinite. Precipitated
crusts of iron and manganese oxyhydroxide were also observed. High magnification studies using a transmission
electron microscope (TEM), reveal that
the halloysite fibres are in fact tubular
crystals possibly formed by the curling
of kaolinite plates.
This article is published with the permission of the Head of the Geotechnical
Engineering Office, Government of the
Hong Kong Special Administrative
Region.
The bedrock includes granite and pyroclastic rocks which are extensively
decomposed to a saprolite often rich in
kaolin-group minerals. Moreover, in
some landslides the rupture surfaces
appear to have developed preferentially
along zones of abundant kaolin-filled
veins and fractures.
1800Å
Above: TEM image of halloysite tube
formed by curling of a kaolinite-crystal.
Left: Cryo-SEM image of kaolinite ‘books’
and halloysite tubes.
12
Ground stability
Ground stability
Subsidence in
the Chalk
Using seismic tomography
ubsidence over the period 1993
to 1997, at the rear of a property
near High Wycombe built in
1830, resulted in substantial
cracking of the masonry structure. In order
to design remedial measures, knowledge
of the extent of disturbed ground beneath
the dwelling was necessary. Crossborehole seismic tomography was identified as the most suitable means of
assessing the ground beneath the property
without disturbing it.
rainwater, resulting in a highly irregular
topography into which sediments were
subsequently deposited. Conical
sinkholes with a central pipe, shaped
like a ‘tornado’, are typical dissolution
features encountered in the Chalk of
southern England. These features
continue to present a hazard today
because, being filled with loose deposits,
they are susceptible to further settlement
and collapse, particularly if drainage
patterns change (often induced by man).
The subsidence occurred in ancient river
deposits (sands and clays of the Reading
Formation) overlying chalk (Upper
Chalk). Previously, when exposed, the
Upper Chalk was dissolved by
During the geophysical survey, sound was
propagated between pairs of boreholes, a
source being in one borehole while
multiple detectors were in the other. The
source and detectors were moved such
Seismic tomography identified an ‘opaque’
volume of ground (high attenuation) to be
associated with the subsidence and to extend
under the rear of the property.
that all possible ray paths (at one metre
spacing) were acquired, providing a
complete, ‘criss-cross’ coverage of the
plane between seventeen pairs of
boreholes. The site, close to a busy road
and generally heterogeneous in nature,
provided challenging conditions requiring
the use of a high power BGS-designed
seismic source. It was found that the
ground associated with the subsidence
was almost ‘opaque’ to the seismic
signals. Consequently, amplitude of the
received seismic wave (rather than time
of transmission) was used to assess the
extent to which the ground under the
property was affected by the subsidence.
The results showed seismically ‘opaque’
ground (blue) to extend under the rear of
the property to a degree that implied the
ground under the house was likely to
subside. The outcome was that the
proposed remedial measures were
deemed to be too expensive, and a new
solution was formulated.
David Gunn © BGS, NERC
S
Peter Jackson © BGS, NERC
by Peter Jackson, David Gunn, Robert Flint, Keyworth,
Michael Bent, 1st Ground Investigations & David Howes,
Broad and Gloyens, Consulting Engineers
Main photo: The Old Vicarage built in
1830.
Inset photo: Cracks in external masonry.
13
Ground stability
Ground stability
Salt subsidence
Geohazard legacy
and future problem?
by Anthony Cooper, Keyworth
alt (NaCl) is essential for life,
necessary for cooking and a basic
mineral for the chemical industry.
It also contributes to winter road
safety. Within Britain it is present as rocksalt mainly within Permian and Triassic
strata from which it has a long history of
exploitation. The main saltfields lie
beneath Cheshire, Staffordshire,
Worcestershire, coastal Lancashire, coastal
Yorkshire, Teesside and parts of Northern
Ireland. Salt, however, is a highly soluble
mineral that can dissolve and cause severe
subsidence problems induced either by
mining or natural causes.
S
In the late 19th and early 20th centuries
the salt deposits were worked by two
main methods: traditional mining and
wild brine solution mining. Most of the
conventional mining was in shallow
"pillar and stall" mines with networks of
tunnels commonly separated by insubstantial salt pillars. Wild, or uncontrolled,
brine solution mining involved sinking
boreholes and shafts down to the wet
rock-salt surface and pumping the brine
out. This wild brine method induced the
flow of brine towards the extraction
boreholes and linear subsidence belts
spread out from the boreholes. In some
situations, mine owners even pumped the
Photo: G. Warke, © GSNI
British salt derived from underground
rock-salt deposits has been exploited since
early Roman times, and possibly before.
Place names ending in "wich" or "wych"
indicate natural brine springs, and it is
around such springs that the towns of
Droitwich, Nantwich, Northwich and
Middlewich developed in Cheshire and the
West Midlands. Coincident with these
near-surface salt deposits, areas of natural
subsidence occur, but these are slight
when compared with historical subsidence
caused by over-zealous exploitation.
Aerial view of the large subsidence crater formed by the collapse of Tennant Mine, Carrickfergus,
County Antrim, NI. The mine was worked conventionally from the 19th Century until the 1920s and
brine was extracted from it in the 1980s. It collapsed at 11.59 hours (BST) on 19th October 1990.
14
Map of the UK showing the locations of
former and present salt mines or extraction
areas.
brine from flooded pillar and stall mines.
Around Northwich and Middlewich, the
resulting subsidence was catastrophic on a
grand scale. Subsidence caused new lakes
to appear on an almost daily basis, and
"meres" or "flashes" many hundreds of
metres across were formed by collapse
after salt extraction. The subsidence in
Cheshire was so severe that an Act of
Parliament was passed placing a levy on
all local salt extraction. This levy, which
funded building reconstruction and compensation payments, is still made, but
collected at a lower rate to reflect the
reduced risk from modern extraction.
Modern salt extraction now takes place
mainly in deep dry pillar and stall mines,
or by controlled brine extraction leaving
large deep underground chambers that
are left flooded and filled with saturated
brine. Current planning procedures
ensure that the modern exploitation lies
largely outside of urban areas so that
risks are considerably reduced. However,
there is still a legacy of problems related
to the salt deposits. These include old salt
mines that have not yet collapsed, and
compressible or unstable collapsed
ground over former salt mines. In
addition, natural salt dissolution at the
rockhead interface, between the salt
deposits and the overlying superficial
deposits, can cause ground engineering
problems and aggressive saline groundwater. The accurate mapping of the rocksalt and associated deposits, and an
understanding of their dissolution and
collapse characteristics, help development and planning in these subsidencesensitive areas.
Ground stability
Ground stability
Collapsing
loess soils
An under-appreciated hazard
by Kevin Northmore, Keyworth, Ian Jefferson, Ian Smalley
& Caroline Tye, Nottingham Trent University
hat do Buckingham
Palace, the Nissan Primera
and hydrocollapse have in
common? The answer is
loess. Loess covers approximately 10%
of the world’s surface. It is a silty soil,
usually light brownish-yellow in colour,
deposited by the wind, and has the
potential to collapse when wetted and
loaded. As a consequence it is a major
hazard in geotechnical engineering. In
Britain the distribution of this material,
although minor, still commands the
interest of geo-engineers.
W
When the BGS first mapped southern
Britain at the end of the 19th century, the
limited deposits of superficial loess
encountered were generally considered as
materials of little scientific interest
masking more interesting rocks. However,
near-surface availability and the inherent
nature of the material enabled it to be used
for brickmaking and the term brickearth
was coined for these deposits. In southern
Britain, by and large, brickearth means
loess — but a terminological confusion
had been introduced. Buckingham Palace
is built from bricks made from the loess of
northern Kent, as was much of suburban
Victorian London. More recent applications have included the use of Essex loess
in mud-splash tests conducted on the
Nissan Primera at the manufacturer’s test
track in Sunderland.
By the mid 20th century, when the Soil
Survey began to map areas of the
southern UK, the extent of loess
material began to be appreciated, with
the most well-known location being at
Pegwell Bay in Kent. However, even
now the extent and nature of loess in
Britain is not fully appreciated.
Described as a macroporous, metastable,
collapsing soil, geo-engineers consider
loess to be a major global geohazard. The
silt particles comprising these soils accumulate by air-fall and a very open soil
structure is formed, which can be maintained following post-depositional
processes. When loaded and wetted the
soil structure may collapse rapidly (a
process called hydroconsolidation)
resulting in ground subsidence and
distress to overlying structures. In many
cases, major subsidence can occur with
buildings being severely damaged or
destroyed. This is a continuing problem in
many parts of the world from China to
Eastern Europe where large tracts of thick
loess deposits coincide with concentrations of people and industry. For example,
in one small district of Lanzhou, China
over 100 of 168 buildings have been
damaged or destroyed as a result of loess
collapse in the last ten years. Loess has
even been mooted as a possible host for
low level radioactive waste disposal. It is
a less significant problem in England, but
in recent years has still caused a number
of houses to be abandoned due to severe
subsidence damage.
In the mid 1970s the BGS completed an
extensive survey in south-east Essex which
included an area designated for major
urban development to accompany the
proposed construction of a third London
Airport at Maplin Sands. The survey investigations revealed the presence of collapsing loess soils up to eight metres in
thickness in the study area. The airport and
accompanying urban development plans
were dropped, but there is no doubt that
had they gone ahead there would have
been some interesting subsidence problems
to solve. The BGS is currently preparing a
major study of the UK loess, in association
with the Geohazards Research Group at
Nottingham Trent University, and it is
hoped that this definitive national study
will give our loess the status that it enjoys
in many other countries.
Main photo: Pegwell Bay, Kent the bestknown loess site in the UK. Cliff section
shows 3 m of brown loess overlying the
Chalk.
Kevin Northmore © BGS, NERC
Inset photo: A scanning electron micrograph showing the typical macroporous
structure of loess from Pegwell Bay, Kent.
The view shows silt-sized quartz particles
coated with clay minerals which ‘bond’ the
particles together making a metastable
structure. The hair-like ‘cobweb’ features
represent the early stages of cementation by
calcite. The clay and calcite bonds break
down when the sample is loaded and wetted
causing collapse of the soil structure into
void spaces.
15
Ground stability
Ground stability
Alan Forster © BGS, NERC
Fault reactivation
An unexpected hazard
by Alan Forster, Keyworth
T
millions of years. However, they do
represent a plane of weakness and can
move if disturbed by a range of activities that change the stresses on them.
Fault movement is clearly seen in the city of
Xian by the disruption of rigid brickwork
and beams in buildings that straddle the
fault trace.
In British coalfields very large volumes
of coal have been extracted from underground mines. This usually causes a relatively gentle lowering of the ground
surface, sometimes by several metres.
However, where a fault is present the
movement may be taken up at the fault
plane itself causing the fault to move
and resulting in a fault scarp, perhaps
several metres high, at the ground
surface. A very clear example can be
seen in the South Wales Coalfield that
can be traced for hundreds of metres
across the countryside. If such a scarp
should impact on surface structures
severe damage can ensue.
eleven major faults, expressed as ridges in
the weakly cemented loess, which move
slowly in a manner called creep. They
have not, in the past, caused insuperable
problems to the city but the area is very
dry and increases in population and
industry have resulted in a greatly
increased rate of extraction of groundwater. The pumping has resulted in a
lowering of the level of the water table and
this has caused the dewatered sediments to
consolidate. Normally this would cause a
gentle lowering of the ground surface, but
in this area the movement was concentrated on the faults, which moved vertically at a maximum recorded rate of 180
millimetres per year. In some areas scarps
up to 500 millimetres high developed,
causing significant damage to roads,
houses and factories. The problem was
eased by decreasing the rate of abstraction.
Another cause of fault activation can be
the abstraction of groundwater. The city of
Xian in central China is founded on a
sequence, 700 metres in thickness, of
river, lake and windblown (loess) deposits
in a fault-bounded basin. The area is tectonically active and the city is crossed by
Alan Forster © BGS, NERC
he crust of the Earth is not an
unbroken mass but is cut by
countless fractures. The largest,
such as the Mid Atlantic Ridge,
define the plates that form the Earth’s
surface on which the continents move
over geological time. The plates themselves are cut by major discontinuities,
called faults, which have formed over
millions of years as a result of the
stretching and compression that the
plates have suffered as they moved
under the influence of convection
currents deep in the Earth. The largest
faults stretch for hundreds of kilometres,
with relative displacements of the
ground on either side of the fault
ranging from metres to kilometres. In
seismically active areas their sudden
movement is the cause of major earthquakes. On a more human scale the
apparently unblemished land where we
live and work is also broken by fractures
or faults that may be on a scale of tens
of metres to tens of kilometres and are
hidden from view by surface deposits,
soil and vegetation. In most areas these
faults are stable and have not moved for
16
Other causes of fault reactivation include
increased pore water pressures as a result
of the disposal of fluid waste down deep
boreholes and increased loading of the
Earth’s crust due to the construction and
infilling of large dams and reservoirs.
These examples of fault reactivation
illustrate the importance of having access
to accurate maps and plans of faults in
areas of development and appreciating
the possible consequences of our activities on the balance of forces that
permeate our surroundings.
Fault scarps in the South Wales Coalfield
believed to be due to reactivation by coal
extraction.
Ground stability
Ground stability
0
Scotland
District
Mudstones
Barbados
ke
H ac l to
's C
l
n
Landslides and
tourist development
10 km
by Chris Evans, Keyworth
he island of Barbados is geologically divisible into two
distinct parts. Most of the island
is underlain by a Pleistocene
limestone cap on average 70 metres thick,
but a sector of the east coast (the
Scotland District) is largely devoid of this
cover and is underlain by structurally
complex Tertiary turbidites and oceanic
bedded and diapiric mudstones. The
island has an asymmetric E–W crosssection, with a steeper eastern side rising
to a height of 330 metres and a much
gentler western slope. The trade winds
blow continuously on to the east coast
but the west coast lies in the lee. In
1997–98 Sir William Halcrow and
Partners carried out a coastal zone management study of the eastern coast for the
Barbados Government, and the BGS
provided geological input to this project.
Professor Robert Speed of Northwestern
University, Illinois carried out most of
the onshore mapping. Tourist development on the island is concentrated on the
sheltered, gentler-sloping south and west
coast, and this project addressed the
potential for tourist development of the
eastern coast. Of specific interest were
the geological hazards which might have
constrained development along this coast.
Geological mapping of the Scotland
District by Professor Speed identified
individual slides with downslope lengths
of up to 1000 metres and thicknesses of
about 40 metres. Motion of the landslides
varies from creep, identified from undulations in those road surfaces, to singular
and rapid flows. The latter are rare but
events in historic times have moved
sheets measuring up to 120 thousand
square metres. The process has been facilitated by high rainfall and rapid flow of
surface water down through the limestone
cap but uncertainty remains about the
sliding mechanism.Damage to the road
system is extensive and dwellings are
locally affected.
The limestone cap rocks move as individual blocks or sheets down the steep slope
towards the sea, where wave erosion
removes the mud matrix and finer
limestone debris to leave behind large
blocks such as those common along the
foreshore south of Bathsheba.
Outside the Scotland District, steep cliffs
of Pleistocene limestone form the east
coast. The high wave energy along this
coast and low tidal range erode deep
wave-cut notches leading to undercutting
and, ultimately, collapse of the cliff. The
process is sporadic and collapse occurs in
sections up to tens of metres long and a
few metres deep. The precise form of the
collapse depends on the strength and diagenesis of the limestone. Understanding
the processes leading to cliff failure is
important in assessing risk at the coast but
this analysis has yet to be carried out.
© BGS, NERC
Barbados is part of a forearc high lying
about 170kilometres west of the oceanic
trench that marks the position of the Atlantic
plate subducting under the Caribbean Plate.
The subduction has caused the island to rise;
evidence from the Pleistocene limestones
suggest that this uplift has gone on for at
least the past 300thousand years and
continues to this day. Present uplift of the
central part of the island is estimated at
about 1.13 to 1.6 metres per 1000 years.
Atlantic Ocean
Sketch map of Barbados; the Scotland
District in the east of the island is the area
most affected by landslides.
Initially the Pleistocene limestone cap
covered the whole island but, as uplift
proceeded, the cap covering the eastern
steeper slopes of the island fractured and
slid downslope. The landsliding was most
active where mudstones underlay the
limestone and the slip planes lay just below
the interface. The process is continuing and
Hackleton’s Cliff (see map) marks the back
scar of the landslide area.
T
N
Steep cliffs of Pleistocene limestone form
the coast. The high wave energy along this
coast and low tidal range erode deep wave
cut notches, leading to undercutting and
ultimately collapse of the cliff.
17
An understanding of the process and
location of landsliding across the area is
essential before the infrastructure
necessary for tourist development can be
put in place. In addition, the dangers
presented by landsliding must be assessed
along with the hazard presented to tourists
by collapse of the coastal cliffs.
© BGS, NERC
iff
The slow slide of eastern
Barbados into the sea
Pleistocene
Limestone
Bridgetown
Coastal and offshore
Coastal and offshore
Paul Tod © BGS, NERC
Cliff stability and
coastal landslides
Rock slide at Beachy Head
by Alan Forster, Peter Hobbs & Robert Flint, Keyworth
n the 10/11th of January 1999
a rock slide at Beachy Head,
East Sussex, took place that
received considerable media
interest due to the relatively large size of
the fall and the prominence of Beachy
Head as a tourist attraction. The fall also
disrupted the electricity supply to the
Beachy Head Lighthouse, founded on
the wave-cut platform at the bottom of
the cliff, and required deployment of the
backup diesel generator.
O
Beachy Head and the Seven Sisters to the
west of Eastbourne are world-famous
both scenically and geologically. The
chalk cliffs expose the complete sequence
of the Chalk from its lowest members up
into a high level in the Upper Chalk. They
have been studied for well over a hundred
years and are now regarded as a type
section because of the completeness of
the sequence and its accessibility. As a
result of the work of Professor Rory
Mortimore of the University of Brighton
and the BGS, the sequence in the cliffs is
used as a standard for mapping across the
whole of southern England.
several years or possibly tens of years.
Hence it is difficult to calculate recession
rates accurately unless detailed cliff
positions are known over a period of
many years. It must also be acknowledged that the spectacular topography
and whiteness of the cliffs are products of
the erosion and, even if recession could
be halted, the nature of the cliffs would
change to the detriment of their value as
notable landscape features.
Cliff stability assessment
As a consequence of the rock slide the
BGS were commissioned by The
Corporation of Trinity House to advise
them on the likely short-term and longterm stability of the cliff. Only with such
information could decisions be made for
maintaining the electricity supply to the
Beachy Head Light. The BGS carried out
an engineering geological survey of the
cliff by inspecting and photographing the
profile and discontinuities in the cliff face.
The work included a geophysical survey of
the cliff top using a high-resolution resistivity imaging technique that looked for
significant discontinuities which would
impair the stability of the cliff but were
hidden from surface inspection.
Representative samples of chalk from the
debris pile at the foot of the cliff were
collected and tested in the BGS laboratories to give values for density, porosity,
unconfined compressive strength, cohesion
and friction angle.
The data gathered from the field and laboratory work were used as inputs to an
analysis of the cliff’s stability, using
GalenaTM limiting equilibrium slope
stability software. This indicated its
current stability and the results were also
used to assist in a long-term stability
assessment. The results of this work have
enabled Trinity House to plan for the continuing supply of electricity to the lighthouse. Following the initial survey a
second minor fall took place on the 8th of
April, removing a portion of cliff which
had been identified during the survey as
highly likely to fall in the near future.
Rob Flint © BGS, NERC
Concern was expressed in the media that
part of our coastal heritage was at risk
and that, given time, Beachy Head would
vanish into the sea. It is true that Beachy
Head and the other chalk cliffs in the area
are receding due to marine erosion at a
rate that has been estimated by various
authors at between 0.25 and 1.2 metres
per year. However, recession is episodic.
The cliffs may recede by several metres
at a single fall and then remain stable for
The January rock slide almost reached the
base of the Lighthouse.
Making a photographic record of the cliff
face from the Gallery of the Beachy Head
Lighthouse.
18
Coastal and offshore
Coastal and offshore
Coastal landslide hazards in Britain
Jim Evans © BGS, NERC MN27778A
Alan Forster © BGS, NERC
Another large landslide, of a very
different character to the Beachy Head
slide described opposite, was the
Holbeck Landslide, south of
Scarborough. This attracted considerable
interest when it destroyed the Holbeck
Hall Hotel in1993. A rotational landslide
involving about 1 million tonnes of
glacial till cut back the 60 metre-high
cliff to a distance of 70 metres. It flowed
across the shore to form a semicircular
promontory 200 metres wide projecting
135 metres outward from the foot of the
cliff. The cause of the slide was attributed to heavy rainfall of 140 millimetres
in the two months before the slide took
place.
Although only the large and spectacular
landslides are reported in the news,
small landslides are common around
our coast and affect a wide range of
geological materials such as soil falls
and slides in the low till cliffs of
Holderness, rock falls from the strikingly coloured red and white chalk cliffs
at Hunstanton (above) and mudflows
from the internationally famous fossiliferous Jurassic cliffs of the Dorset coast.
Jim Evans © BGS, NERC
Landslides are a constant feature of the
development of our coastline and at any
time there will be active landslides in
many places, most are due to natural
causes such as marine erosion, high
rainfall or the natural weakening of
rocks through weathering.
Jim Evans © BGS, NERC
A large slump in glacial till led to the destruction of the Holbeck Hall Hotel,
Scarborough in June 1993.
Mudflows of Lias clay and sand runs from the Upper Greensand form the Black Ven
landslide complex on the Dorset coast, east of Lyme Regis.
19
It is important to take into account the
possibility of rock falls from cliffs when
enjoying the recreational potential of
our coast both by being careful to avoid
walking at the edge of unstable cliff
tops and taking care to keep away from
the base of cliffs which have overhanging rocks on the point of falling. On a
larger scale, all construction work near
to cliffs should take expert advice on
cliff stability issues at the time of construction and projected into the design
life of the structure being considered.
The cost of such surveys and predictions is money well spent as illustrated
by the bungalow at East Cliff, Dorset
(above) that was carried over the cliff
edge by landsliding about one year after
its completion.
Coastal and offshore
Estuarine
contamination
A present and potential
environmental geohazard
by John Ridgway, Keyworth, Steve Rowlatt, Centre for Environment
Fisheries and Aquaculture Sciences & Peter Jones Environment Agency
any major estuaries in
Great Britain (e.g. Forth,
Tyne, Tees, Humber,
Thames, Solent, Tamar,
Severn, Mersey, Ribble and Clyde) are
sites of urban, port, industrial and recreational development. They are also
important for nature conservation,
providing nationally and internationally
significant habitats for birds and marine
life. Unfortunately, man’s activities frequently have a detrimental impact on
nature and our estuaries provide
abundant examples of past damage.
They also are threatened by present and
future environmental hazard.
M
Estuaries form the link between river
systems and the sea and sediment from
both land and sea sources can be
deposited there. River waters and
sediment carry contaminants from
mining, industrial and agricultural activities in the hinterland, developments on
the shores of the estuary input wastes
directly, whilst tidal currents bring in
water and sediment from offshore.
These latter might, for instance, have
moved along the coast from towns and
industry, or have come from further out
to sea carrying unwanted products of
shipping or the hydrocarbon industry. At
the present time, both organic and
inorganic contaminants in sediments
may be buried and in storage, undergoing remobilisation, or being deposited;
their distribution may be influenced also
by the activities of organisms such as
shellfish and worms and gradual
changes in chemistry may increase their
uptake by marine animals. Much is
being done to reduce the release of contaminants into the environment from
industrial, urban and agricultural waste,
but there is a shortage of knowledge
about the types, amounts and locations
of contaminants stored in sediments.
The Mersey is a good example of a contaminated estuary, having suffered a legacy
of abuse and neglect since the beginning of
the Industrial Revolution. The discharge of
effluents from manufacturing processes,
together with wastewater from the burgeoning centres of population, resulted in
the estuary gaining the unenviable reputation of being one of the most polluted in
Europe. Whilst the long-awaited remedial
actions, taken over the past two decades,
have unequivocally reduced the concentrations of dangerous substances currently
being deposited, in some instances to preindustrial levels, vast quantities of potentially hazardous substances remain locked
up in the sediments. However, we do not
know enough about the distribution of the
contaminated sediments to be able to
predict the consequences of flood defence
and drainage activities upstream, dredging,
port and industrial development along the
estuary shores, or operations and natural
processes in the coastal zone, including
sea-level rise due to global climatic
change.
In recognition of the problems of contamination, the Marine Pollution
Monitoring Management Group of
Department of the Environment,
Transport and the Regions decided that
there should be regular sampling of a
network of coastal and estuarine monitoring stations around the UK, which
20
should include some that are not
expected to be significantly contaminated. Responsibility for the monitoring
of biological, physical and chemical
determinands at these stations lies with
the Environment Agency; Scottish
Environment Protection Agency; Centre
for Environment, Fisheries and
Aquaculture Sciences; Scottish Office
Agriculture, Environment and Fisheries
Department; or Department of
Agriculture for Northern Ireland/
Department of the Environment,
Northern Ireland; depending on the
location of the stations.
This national programme produces a
coordinated and reliable national data
set on sediment contaminants in inshore
and coastal waters, but it does not
address the problem of the storage of
contaminants in sediments and the prediction of the environmental impact of
their movement due to man’s activities
or natural processes. To this end, the
BGS is planning a survey programme
which will attempt to map the distribution and thickness of contaminated
sediment in major UK estuaries as an
aid to coastal zone management.
Survey boat taking samples on the Mersey
estuary.
P D Jones © Environment Agency
Coastal and offshore
Coastal and offshore
Coastal and offshore
Relative
sea-level rise
Vulnerability, risk and
research priorities
by David Brew, Keyworth & Russell Arthurton,
Coastal Geoscience Consultant
elative sea-level rise is the
increase in mean sea-level, at
any given coastal location,
compared to the level of a
reference point on the adjacent land
surface. The process leads to an increase
in frequency and severity of marine
inundations of low-lying coastal land
and, in the absence of engineering intervention, to long-term inundation. The
assessment of relative sea-level rise is
difficult, due to the large number of contributory processes involved, on global,
regional and local scales.
R
At the end of the last glacial period, global
(eustatic) sea-level began to rise. About
10 thousand years ago the global level was
about 60 metres below present. Sea-level
rise was rapid at first (20 metres every
thousand years) then slowed down after
about 6000 years before present. However,
the possibility of future accelerated sealevel rise, as a consequence of maninduced global climate change, is now a
major threat to coastal lowland communities. The forecast for total eustatic sea-level
rise over the next 100 years ranges from
31 centimetres in the best case scenario to
110 centimetres in the worst.
response to sediment loading. At the local
scale, natural physical processes and
human interventions may lead to land subsidence over the short term, at rates in
excess of those predicted for eustatic sealevel rise. Subsidence related to local
sediment consolidation is important in this
respect. The over-abstraction of groundwater and dewatering of the sediments due
to surface loading are particularly
important contributors.
While the vulnerability of coastal areas to
relative sea-level rise can be geographically defined and quantified, the multigenic
nature of this hazard (as discussed above)
makes risk assessment difficult. The likely
incidence and severity of relative sea-level
rise, in terms of the rates and the changes
Regional circumstances may exacerbate
relative sea-level rise in some coastal
areas. For example, regional neotectonic
subsidence may have been occurring over
millions of years at some sites. Also acting
at the regional scale are processes associated with isostatic readjustment of the
Earth’s crust, such as downwarping in
Flooded agricultural land at Salthouse,
north Norfolk coast.
21
of those rates with time, may be poorly
known. While one coastal area may be
stable, a large area elsewhere may be
subject to marine inundation. Therefore it
is important to understand how coastal
lowlands have developed in relation to
rising sea-levels in the past and how these
responses are likely to differ in the future
as man’s influence increases. The BGS is
presently studying these aspects as part of
its Coastal and Estuarine Evolution Core
Programme activity. The BGS holds
extensive datasets that allow the evolution
of coastal lowlands to be evaluated in
terms of their sea-level history, allowing
modern data to be placed into a long-term
context. Combination of these data with
data on eustatic sea-level change, surface
elevation (digital terrain mapping techniques) and future land-level change (for
example, geotechnical consolidation of
lowland sediments) provides a powerful
tool to predict responses to, and quantify
the risk of, future relative sea-level rise in a
range of possible vulnerability scenarios.
The Coastal and Estuarine Evolution
research project is developing innovative and transportable methodologies
and conceptual models of coastal
evolution, particularly in the fields of:
●
Relative land-level changes and
flood risk
●
Coastal erosion and sediment
budgets
●
Estuarine geomorphology
Coastal and offshore
Coastal and offshore
The Western
Frontiers Association
Geohazards in a frontier area
by David Long, Edinburgh
joint industry group was established in 1995 by the BGS to
investigate sea bed conditions
and evaluate geohazards west
of the UK. The group, known as the
Western Frontiers Association (WFA),
comprises 14 oil companies and the
Health and Safety Executive (Offshore
Safety Division) (HSE). The WFA was
formed following a regional study by the
BGS, for the HSE, two years earlier. This
study demonstrated that ground conditions to the west of Britain, were more
varied than in the North Sea and that
processes and hazards were less well
The group initially focused on the area
west of Shetland following the upsurge of
interest after the Foinaven and
Schiehallion oilfield discoveries.
Following the 17th round of licensing in
1997, the areas of focus were extended to
include the Rockall Trough and the
margin north of 61° 40'N. The group has
commissioned a wide
range of studies to assess
geohazards such as
shallow gas, slope stability
N61°22
and methane hydrates on a
regional basis. Reports
have been produced on
these topics along with an
atlas of hazards. Data
N61°20
acquisition has been undertaken on a regional basis
and combined with
operators’ data and the
BGS’s previous regional
535000E
530000E
525000E
A
understood. The WFA is similar to, and
relates with, other joint industry groups
covering oceanographic data (North West
Approaches Group) and environmental
matters (Atlantic Frontiers Environment
Network).
6800000N
N61°18
6795000N
6790000N
W2°24
W2°28
N61°14
W2°32
M Sankeyt © BGS, NERC
N61°16
The AFEN slide, situated
some 90 km north-west of
Shetland on the
Faeroe–Shetland Channel
slope at 500 m water depth.
The slide is 13 km long and
3 km wide on a slope of one
degree. The image has been
created using the first (sea
bed) acoustic signal return
from a conventional 3-D
exploration seismic data set.
22
surveys to complement studies acquired
by the commercial site survey industry.
Seismic (earthquake) monitoring has been
under way for more than three years to
aid risk assessments.
The principle focus of the WFA is the
examination of geohazards, in particular
the type of hazard, its location, size,
frequency, activity and how it may affect
temporary or fixed structures placed on
the seabed. The earlier study for the HSE
identified that west of the UK there were
geological hazards not encountered in the
North Sea. These include iceberg ploughmarks, debris flows and hydrates. More
recent studies have also identified the
presence of shallow faults, and sea bed
mounds that may need to be considered in
planning sea bed activities.
Occasionally, small area studies, such as
the evaluation of landslides, have been
undertaken to examine a hazard in
detail, where the results can be extrapolated regionally. The illustration shows a
sea bed slide 3 kilometres wide and
13 kilometres in length extending from
800 metres water depth in the south-east
to 1200 metres water depth in the northwest. This slide has occurred within the
last ten thousand years and is interpreted
to have been a multiple event caused by
repeated failure of the back scarp
causing retrogressive failure upslope.
The results of the studies commissioned
by the WFA have applications beyond the
site survey sector. A wide range of
physical processes have shaped the sea
bed west of Shetland, creating environments that may influence benthic biota as
well as affecting structures placed on it.
Studies of the movement of sediments
may assist modelling of cuttings distribution and sea bed morphology studies are
improving oceanographic modelling of
the Faeroe Shetland Channel. The results
of these studies have been presented in
the form of reports, maps and databases
supported by software developments.
The WFA grouping collaborates with
other joint industry programmes looking
at sea bed geology and geotechnics on
similar margins such as the Seabed
Project on the Norwegian margin and
similar groups for areas offshore Ireland
and the Faeroes.
For further information, visit the WFA web-page at:
www.bgs.ac.uk/bgs/w3/pmgg/pmg_wfa1.htm
Urban and health
Urban and health
Urban geohazards
this project will also develop a prototype
geohazard risk assessment GIS,
designed to support the decisionmaking, planning and development
control functions in municipal governments across Europe.
A European perspective
by Andrew Howard, Keyworth
ery few hazards are truly
‘natural’. Many are triggered,
or at least worsened, by man’s
interaction with the natural
environment. This is especially true in
cities, which greatly increase the
incidence of hazards and amplify their
effects. Cities concentrate population,
economic assets and heritage into small
areas. To function, they depend on a
complex and interdependent infrastructure of services, utilities and transport
networks. Cities and their inhabitants
are therefore highly vulnerable to the
effects of natural hazards. Furthermore,
with the globalisation of the world’s
markets, the effects of a ‘local’ disaster
may no longer be isolated to a single
city. It has been speculated, for example,
that the domino effect of a catastrophic
earthquake affecting Tokyo could lead
to ‘meltdown’ of the global economy.
V
Despite the wide reporting of major
natural disasters, statistics on the associated human and economic costs in
Europe are surprisingly hard to find. The
best figures relate to 1993, when natural
disasters cost the lives of 500
Europeans, with geohazards accounting
for 400 of these. In the same year, the
total economic losses due to natural
disasters in the EU was 3 billion euro,
mostly counted in cities. The frequency
and impact of hazards are continuing to
grow. In 1990–96, losses due to landslides and floods in Europe were 4 times
those of 1980–89 and over 12 times
those of 1960–69. Globally, the number
of people affected by natural disasters
rises by 6% every year.
These statistics cover only the major
disasters that make the news, but other
less ‘spectacular’ hazards may have a
far greater, cumulative economic cost.
In the UK alone, for example, property
damage caused by shrink-swell of clay
soils accounted for 700 million euro of
insurance claims per year in the
“... in the UK alone, for
example, property damage
caused by shrink-swell of clay
soils accounted for 700 million
euro of insurance claims per
year in the early 1990s ...”
early1990s. Tens of thousands of properties in France were damaged by
shrink-well during the same period.
The national geological survey organisations of the 15 member states of the
European Union, together with Norway,
collaborate in the non-profit association
EuroGeoSurveys, which provides advice
and information on geoscientific issues
to the European Commission, the
European Parliament and other EU institutions. Since 1996, EuroGeoSurveys
has been comparing the wide range of
geohazards affecting Europe’s cities and
has prepared an inventory of their
effects.
More than two thirds of Europeans now
live in cities, and the proportion is continuing to grow, especially in southern
Europe. Despite their enormous social,
economic and environmental diversity,
all cities face the common challenge of
minimising the costs of natural hazards.
The information provided by EuroGeoSurveys will enable city governors and
planners to assess the risks posed by
geohazards and manage them effectively, in balance with other priorities.
This is a key objective of ‘the sustainable European city’, and will provide the
urban dwellers of the future with a safe,
healthy and economically competitive
environment in which to live and work.
EuroGeoSurveys is currently seeking
EC funding to establish EU-wide guidelines and best practice for mapping the
extent of geohazards in Europe’s cities
and assessing the associated risks. In
partnership with cities across the EU,
Country abbreviation
Geohazard
A
B
D
DK
E
F
FIN GR
IRL
I
LUX NL
N
Failure of foundations
Ground collapse
Landslides / rockfalls
Erosion and siltation
Earthquakes and volcanoes
Natural radiation
Inland / coastal floods
Contaminated land
Groundwater pollution
Surface water pollution
Urban wastes
Extent of problem
High
Medium
Low
Modified from Geoproblems of urban areas in the EU and Norway, EuroGeoSurveys, 1998
Breakdown of main geohazard types by European country.
23
P
S
UK
Urban and health
Urban and health
Earthquakegenerated ground
motion amplification
Assessing the hazard in
urban Costa Rica
by Peter Jackson, David Gunn, Martin Culshaw
& Alan Forster, Keyworth
round motion amplification
(GMA) is the increase in
amplitude of seismic waves
as they pass from harder to
softer rocks, plus increases in amplitude
due to interactions within ‘basin’ structures containing soft sediments.
This requires an understanding of the
seismo-tectonics affecting the region, a
site-scale layer model of the lithologies
from the rock basement to ground surface,
data on the geophysical properties of each
layer, and digital seismograms of representative earthquakes that would affect
the site.
G
Many of the massive urban developments,
or megacities, are founded on flat-lying soils
that are relatively easy to engineer. They
often coincide with alluvial basins, deltas
and lake deposits, where unconsolidated
sediments overlie consolidated, crystalline
or cemented bedrock. In these circumstances, GMA can pose a serious threat.
San José, Costa Rica’s capital, is
situated on the interbedded deposits of
lahar of a clay-silt matrix with andesite
clasts and andesitic lava flows. Cartago
is situated on a sequence of fine sand
and clay lake deposits, 60 metres in
thickness, in a shallow basin within the
lahar and lava flow deposits. All these
deposits are underlain by sandstone.
The histogram shows that most of the
A full evaluation of the GMA hazard
should be undertaken deterministically.
South
0
North
Cartago
Horizontal scale
(Not to Scale)
5km
Acceleration (g)
Sandstone
0km
Top Volcanics
x3
Top Sandstone
x2
10
5km
10km
Depth (m)
200
Depth
and
Andesitic Lava Flows
60m
140m
Depth (m)
Fine Sand and Clay
Interbedded Sequences of
Clay and Silt with Andesite Clasts
5
Amplification
0.05 0.1 0.15 0.2 0.25
Top Alluvium x6
100
No of Earthquakes
Borehole Log
David Gunn © BGS, NERC
0
0
300
400
500
Hypocentre
600
Section showing the cumulative amplification of an earthquake as it passes from hard rocks to
soft alluvium beneath Cartago.
24
earthquakes in the locale occur within
10 kilometres of the Earth’s surface.
Even earthquakes of medium
magnitude can cause severe damage
because of the combination of
proximate shallow earthquakes and the
susceptibility of the Cartago basin to
GMA. The model results show the
amplifying effect of the Cartago basin
in comparison to the ground motion
suffered in the lava and lahar deposits.
Cartago regularly suffers more damage
than San José. The peak horizontal
acceleration of seismic waves is
amplified as they propagate up from the
hypocentre because the rocks get
weaker towards the surface. The amplification factor is only threefold at the
top of the interbedded lavas and lahars
where San José is situated but is sixfold
at the top of the alluvium where
Cartago is situated.
It is apparent that there is a very low
level of awareness of the hazards associated with earthquakes. Small-scale
surveys alone would improve
awareness of the possible hazards in
these areas, and this in itself is
requested by politicians and national
planners. Even in areas like the Central
Valley of Costa Rica which are well
studied it is apparent that regional and
district-scale studies are required to
characterise the local impact of
hazards. Aspects of future work include
further regional studies to map the
occurrence of GMA and other earthquake-induced hazards, and greater
exchange between geologists and
planners such that geological information is input directly into planning
decisions.
In conclusion, it is imperative for the
geological framework to enter the
planning process, as it provides simple
guidance to the areas of least and
highest susceptibility to GMA.
This information feeds directly into
policies for building regulations and
design. For example, buildings in
Cartago should be designed to withstand
greater ground accelerations than
buildings in San José. However, often
this is not the case due to a lack of
awareness amongst planners of the geological controls on hazards. This
situation needs to be addressed if the
damage associated with earthquakes is
to be minimised.
Urban and health
Urban and health
Tsunamis and the
urban environment
avoided. Such high risk areas are the lowlying playas on the Caribbean coast to the
south east of Limon where a magnitude
7.5 earthquake caused a tsunami in 1991.
The tsunami struck the coast between
Limon and the Panamanian border.
Tsunami arrival times along this section
of the coast were generated about the
axis of maximum uplift which runs
parallel to the coast between three and
eight kilometres offshore in seawater of
approximately 50 metres depth. The axis
of uplift intersects the shoreline just to
the north of Limon where it caused the
sea to retreat by 75 metres. It also completely destroyed buildings on the
shoreline like the Hotel Las Olas
featured in the photograph.
Implications for national and
regional planning
by David Gunn, Martin Culshaw, Alan Forster
& Peter Jackson, Keyworth
84
Location of the
Hotel Las Olas
10
San José
M 7.3 - 7.5
M 7.0
Pacific Ocean
Tsunami Susceptibility
Map of Costa Rica
High Susceptibility
M 7.4 - 7.6
Limon
M 7.0
The tsunami risk to the coastline of
Costa Rica is indicated, along with the
location of the axis of the source for the
1991 tsunami. The light blue areas are
potential seismic sources with estimates
of magnitude.
M 7.3 - 7.5
84
David Gunn © BGS, NERC
The coastal topography of Costa Rica is
varied, ranging from low-lying coastlines
and enclosed playas (beaches), through
rocky headlands fringed with coral reefs
to coastal cliffs in hard rocks. The lowlying coastlines and playas are most vulnerable to inundation from the run-up of a
tsunami and the rocky headlands with
coral reefs are most vulnerable to flooding
by a tsunami overtopping a high protective structure. Assessing the susceptibility
of these areas to the tsunami hazard
begins by considering the likelihood of a
particular section of coastline being in the
proximity of an offshore seismic source.
Such maps can readily be drafted by a
seismologist. As an example, the Tsunami
Hazard Susceptibility Map for Costa Rica
offers a first look-see at the risk to the
coastline from the tsunami hazard. This is
N I CA R A G UA
M 7.2
Possible Axis of the
Tsunami Source
T
Information gained by undertaking the
tsunami hazard assessment can be used to
organise the land-related factors taking
into account the roughness and friction
created by buildings, trees and engineered
structures to minimise the potential for
destruction. So, a ‘Tsunami Aware Plan’
for the organisation of these elements
would be to locate the residential, lifeline
and access routes beyond the estimated
inundation zone, but to build in
some contingency for protection
should this estimation be conservative, for instance by planting
trees between the urbanised area
and the coastline.
very useful for National Scale Planning as
it quickly characterises the coastline
tsunami susceptibility into the three broad
categories of low, medium and high.
While planning at the national scale, it
can readily be seen that coastal areas near
to potential seismic sources, shown as
light blue areas with an estimate of
magnitude, represent a high risk where
more detailed planning cannot be
P A N A MA
sunamis are described as long
water waves with periods
greater than five minutes. They
are generated impulsively by
mechanisms such as exploding islands,
submerged landslides, rock falls into
bays and tectonic displacements associated with earthquakes. To reduce the
risk of tsunamis it is necessary to obtain
an understanding of the geological
processes that control them and of the
distribution of the areas that are susceptible to them. It is then possible to assess
the level of hazard so that structures can
be located in areas where it is lower.
The exposed coral reef in front of the Hotel
Las Olas indicates the pre-earthquake
shoreline.
25
Urban and Health
Urban and Health
Mines and bombs
Using geophysics to
expose buried hazards
by David Beamish & Steve Shedlock, Keyworth
or those of us called upon to
investigate the near surface, the
maxim ‘always expect the unexpected’ is often appropriate.
Potential hazards can lie just a few feet
below our buildings, roads and fields.
The BGS was recently commissioned to
undertake a geophysical survey across
playing fields prior to the construction
of a new sports complex. The area is a
typical urban setting in north-east
England. It was known that, during the
last war, a number of bombs had been
dropped in the vicinity; up to six 1000 lb
bombs were indicated. Surveys to locate
such objects are necessarily noninvasive (!) and are conducted using
geophysical techniques.
F
Second World War bombs are part of
the wider problem of the detection of
Unexploded Ordnance (UXO). UXO
detection is a highly developed science
and different problems are presented by,
for example, small arms munitions and
mortars. The U.S. Army and Department
of Defence have excellent information
on the subject on their web pages at
http://www.jpg.army.mil/. A variety of
geophysical screening tools can be used
to locate UXO at depths of up to about
six metres, depending on size, geometry
and material type. A 1000 lb bomb is
considered a high visibility target. Due to
the iron-based material of the shell, a
magnetometer can be used to locate the
object by detecting irregularities in the
Earth’s magnetic field.
The playing fields were surveyed using
a combined sensor that measures both
the magnetic field and its gradient to a
The magnetic field across an area of
100x100 metres shows two main anomalies
(high values in red). The smaller up-down
anomaly is due to the large bomb; the second
anomaly is due to the mineshaft.
David Beamish/Steve Shedlock © BGS, NERC
very high accuracy. The survey results
revealed a typical dipole (up-down)
anomaly that would be associated with a
large concealed bomb. In addition to the
signature from the bomb, a much larger
anomaly, of unknown origin, was also
detected. Historical maps and records
dating back to the previous century were
consulted. It then became clear that our
anomaly was likely to be associated
with the Burdon or Collingwood Main
collieries that ceased operation in the
1820s. The prime suspect became a
shaft associated with the Hopewell Pit
that penetrated a number of coal seams
to a depth of 169 metres.
© Kevin Moir
UXO clearance is always left to
munitions specialists; the larger engineering problem was, in fact, the mine.
A drilling contractor excavated the large
anomaly. A few feet below the surface
of the running track lay a thin, ageing
concrete raft sitting across original
timbers. Both were scraped away to
reveal a three metre-diameter open shaft
that continued to a depth of at least 50
metres. The Victorian engineering of the
shaft was impressive but then so was the
scale of the potential hazard they left.
Excavation of the large anomaly reveals the
3 metre-diameter open shaft of the Hopewell
Pit that closed in the 1820s.
26
Urban and Health
Urban and Health
A diet of dirt
Neil Breward © BGS, NERC
The benefits and dangers of
eating soil
by Barry Smith, Keyworth
C
Geophagia is considered by many nutritionists to be a in-built response to nutritional deficiencies resulting from a poor
diet often rich in fibre but deficient in
magnesium, iron and zinc (essential
nutrients during motherhood, early
childhood and adolescence). Such diets
are common in tropical countries, particularly where the diet is dominated by
starchy fibre-rich foods such as sweet
potatoes and cassava. The theory of
geophagia as a subconscious response to
dietary stress must be balanced against
the habitual eating of soil that has been
reported to develop into extreme, often
obsessive, cravings immediately after
rain. For example one woman interviewed during our studies said ‘You can
neither sleep nor have appetite for food,
until you taste some soil’ whilst another
stated that the urge for soil consumption
was particularly strong after rain ‘The
soil smells nice wherever you go, either
in kitchen, the latrine, and in the field’.
Typical quantities of soil eaten by
geophagics in Kenya were about 20
grammes per day. Whilst eating such
large quantities of soil increases
exposure to essential trace nutrients, it
also significantly increases exposure to
potentially toxic trace elements especially in areas associated with mineral
extraction, or polluted urban environments and biological pathogens.
Similarly, inadvertent ingestion of soils
increases exposure to toxins associated
with contaminated land sites within the
United Kingdom and Europe. Analysis of
exposure scenarios indicates that the
direct ingestion of even minimal quantities of soil by the young can account for
more than 50% of their total exposure to a
given pollutant from all other sources.
This is due to the much higher concentration of contaminants in soils compared to
foods and drinking water sources.
Mine waste: a potential source of toxic trace
elements.
The BGS has been undertaking research
to investigate the potential bioavailability of major and trace elements within
soils commonly used by practising
geophagics in Uganda. It is also investigating the bioavailability of potentially
toxic trace elements such as arsenic and
lead in UK soils associated with a range
of contaminant sources (e.g. mine
wastes, mineralisation, industrial sites).
The objectives of these projects are: (a)
to increase our understanding of the
risks and benefits associated with
geophagia and; (b) to enable the
bioavailability of a particular contaminative source to be accurately taken into
account during site-specific risk assessment. Whilst the latter is unlikely to
reduce significantly the remediation
requirements for grossly contaminated
sites, it is likely to reduce the need for
remediation of marginally contaminated
soils such as those associated with
diffuse pollution and the periphery of
pollution plumes.
Paul Tod © BGS, NERC
hildren and young adults the
world over may be exposed to
chemical elements in soils
through either accidental or
deliberate ingestion of soil, or dusts
derived from soils. In Europe and North
America such exposure probably originates principally from accidental
ingestion during hand-to-mouth contact.
However, in many ancient and rural
societies exposure occurs principally
through the deliberate ingestion of soil,
or soil-derived ‘medical’ preparations.
Such behaviour is medically known as
either pica (the eating of unusual
objects, cf. Pica pica the magpie) or
more specifically as geophagia.
Geophagia is common among traditional
societies and has been recognised since
the time of Aristotle. Soil may be eaten
from the ground as a paste, but in many
situations there is a cultural preference
for soil from ‘special sources’, such as
termitaria, or from traditional herbal-soil
mixes. These preparations may be taken
as a ‘special remedy’ during pregnancy
and by children. It remains a matter of
conjecture whether the soil itself is an
active component of the preparation or
simply a binder.
Herbal remedy Pregnancy: Uganda
27
Urban and health
Urban and health
Vicky Hards © BGS, NERC 1999
Airborne particulates
Monitoring and characterisation
by Vicky Hards, Keyworth
M
Increasing concern over air quality worldwide has accelerated research into the field
of particulate monitoring and characterisation. In the UK, the 1990 Environmental
Protection Act empowered authorities to
prosecute polluters; section 79(1)(g) allows
pre-determined limits to be set for ‘any
dust arising from industrial trade or
business and being prejudicial to health or
a nuisance’. Dust is not only a nuisance in
the domestic setting, there are also
concerns about its impact on business, vegetation and public health. World-wide,
recent high-profile natural disasters, such
as the eruptions of Mount Pinatubo and the
Soufriere Hills volcano in Montserrat, have
raised the question of the health implications of fine volcanic ash for the local
inhabitants. In the UK, asthma is on the
increase, especially among children, and
there are increasing numbers of successful
compensation claims by former miners
suffering the effects of coal dust inhalation
(such as silicosis), and those exposed to
asbestos or other harmful or toxic particulates in the course of their work.
Particles below 100microns may not be
visible to the naked eye, but may be inhaled
and those smaller than 10microns may
penetrate deep into the lungs. The need for
monitoring has therefore been recognised,
and many networks put in place to monitor
PM10 (particulate material less than
10microns in aerodynamic diameter; a
nominally respirable fraction). Sampling
may be by active or passive means, either
relying on wind and precipitation to bring
particulates to the dust gauge or drawing air
through a filter by means of a pump. Passive
deposit sampling systems have the
advantage of being relatively inexpensive,
although requiring long periods of exposure,
typically one month.
The BGS now owns a set of the favoured
‘Frisbee-type’ dust deposit gauges. These
consist of a collecting bowl resembling
an up-turned Frisbee with a foam insert
to prevent collected particulates being
blown back out. Dust dispersion from a
potential source (such as a quarrying
operation) may be established using
clusters and/or traverses of deposit
gauges to establish both the rate of dropoff and to collect samples for ‘fingerprinting’ to confirm provenance. This
may be done through methods of analysis
commonly applied to geological
materials. X-ray diffraction analysis is
used to examine the mineralogy of crystalline samples, the ratios of the various
components may be used to measure the
drop-off of inputs from individual
sources. Both Scanning Electron
Microscopy (SEM) and Energy
Dispersive Spectrometry (EDS) may be
used to determine size, sphericity, form
and chemistry of discrete particles.
Typically, a marked drop in average
particle size is observed with increasing
distance from source. Sensitive chemical
analytical techniques such as Inductively
Coupled Plasma Mass Spectrometry are
also available to further characterise the
bulk composition.
28
Above: Secondary electron SEM
image, showing angular particulate
materials collected using a dust
deposit gauge on the margins of a
working limestone quarry. The large
grain in the centre of the field of view
is an alkali feldspar.
Below: ‘Frisbee-type’ dust deposit
gauge in use. It is positioned within one
of Derbyshire’s working limestone
quarries, in close proximity to the
crusher, a potential source of fine
particulates.
Vicky Hards © BGS, NERC 1999
any natural processes as well
as human activities generate
fine particulate aerosols containing a wide range of components. The largest particles that can be
maintained in suspension by air currents
and eddies are about one millimetre
(1000 microns) in size. These aerosols can
affect the rural and urban environments,
both close to and at great distance from
source. They include mineral grains, biological particles, soot, salts, fragments of
metals and alloys, etc. The mineral (i.e.
inorganic) component is derived both
from natural processes (sea spray, forest
fires, volcanic activity and deserts — red
dust from the Sahara is regularly
deposited over Europe) and man’s activities (traffic, civil engineering, exposing
soil to wind abrasion through agricultural
practices, and industries such as mineral
extraction, quarrying and cement works).
Urban and health
Urban and health
Montserrat ash
A potential hazard to health
by Dick Nicholson, Vicky Hards & Barbara Vickers, Keyworth
he Soufriere Hills volcano on the
Caribbean island of Montserrat
started erupting in July 1995. At
the height of the eruption it
became necessary to evacuate much of
the population to neighbouring islands
such as Antigua, and further afield to the
UK. The main phase of the eruption
appears to be over (early 1999) and
evacuees now wish to return to their own
homes. However, the accumulated
volcanic ash deposits are hampering the
resettlement of many areas and rendering
it almost impossible in others. Living in a
dusty environment for a prolonged period
is likely to have implications for the longterm health of the population, as has been
shown by epidemiological studies carried
out during the eruption.
T
rocks contain silica, and depending on
their composition, and the duration and
type of the eruption, this may be in a
toxic form, with the potential to cause
silicosis, a disease more commonly associated with the mining industry.
There are three main forms of crystalline
silica: quartz, tridymite and cristobalite, and
an amorphous form more generally known
as opal. At high temperatures quartz inverts
to tridymite, which in turn inverts to cristobalite. Of these cristobalite is known to be
the most toxic, and in prolonged high-temperature eruptions, may be the dominant
form. At the Soufriere Hills, the crystalline
silica content of the fine ash smaller than
10µm from pyroclastic flow material
released during collapse of the andesitic
lava dome, was found to be high, ranging
10 to 24 weight percent.
X-ray diffraction is the preferred
technique for identifying the minerals
present in volcanic ash, although the
amounts of the individual components
cannot always be quantified. In order to
obtain a better estimate of the proportions of crystalline silica present,
chemical leaching techniques designed
to isolate the crystalline silica from the
other minerals in the ash have been used
effectively at the BGS. The purity of the
silica residue can then be verified
against the diffraction pattern obtained
for the whole rock, as shown in the
diagrams. In this particular sample
cristobalite is identified as being the
principal silica mineral present.
Vicky Hards © BGS, NERC
Vicky Hards © BGS, NERC
Volcanic ash is a potential hazard to
human health for two principal reasons.
When freshly erupted, or remobilised by
atmospheric disturbance, fine particulate
material (smaller than 10µm) can be
inhaled and lodge in the lung, and even
finer particles smaller than 2.5µm (the socalled respirable fraction) can penetrate
even deeper into the lung. All volcanic
Above: X-ray diffraction profile of bulk ash
sample.
Left: X-ray diffraction profile of silica
residue separated from bulk ash.
29
Urban and health
Urban and health
The legacy of mining
water which would have been technically
insurmountable at this time. The technical
limitations would have limited working to
depths of about 600 feet.
Tracing the hazards using
geological archives
Close to a line of four of the shafts located
in the centre of the study area, a chimney
was mapped, in 1805, which it is assumed
was an engine house for the pumps. All
traces of this structure have disappeared
although the field in which it was located
is locally known as the ‘brick field’, presumably due to debris from the destruction of the previous building.
by Steve Shedlock, David Beamish
& Lorraine Williams, Keyworth
G
Inspection of four geological maps
covering the investigation area showed
that workings at Blundells Colliery have
dominated the area since before 1805
(the earliest geological map for this
area) although mining had been noted
for some two thousand years.
mapping, these workings were
abandoned. There had been considerable
expansion of mining in the area during
the first half of the 19th century and this
development required infrastructure
links, resulting in the construction of the
railway to serve Blundells Colliery.
Barge traffic on the Leeds and Liverpool
Canal had also increased.
During 1861, remapping of the geology of
the area showed a stable industrial history
of mining activity within this part of the
Lancashire coalfield. All mine shafts were
now shown to be abandoned. This rapid
decline could have resulted from the
necessity for greater mining depths with
the associated abstraction of deep mine
The geological map of 1805 indicated
that supposed Roman workings were
found in the area of Arley Hall located
to the south-west of the study area.
Surveyed prior to the construction of a
mineral railway on the east of the canal,
the base map showed a limited number
of working mine shafts associated with
Blundells Colliery. Features such as the
culvert passing under the Leeds and
Liverpool Canal are still in existence
and indicate that surface run-off
problems were evident at the time of
construction of the canal. A further
culvert was subsequently constructed
under the mineral railway between 1805
and 1847 to maintain this drainage path.
By 1847 (the next time slice within the
mapping) considerable expansion of
Blundells Colliery had occurred and apart
from the construction of the railway, the
number of mine shafts had increased
threefold. The earliest map of 1805 had
shown that all of the mine shafts were
active; however by the time of the later
Inspection of later geological maps of
1861, 1896 and 1905 showed little
change in the study area with indications
of mine shafts being maintained. All
mine shafts were abandoned and little
detail of mine abandonment could be
found; these mines had closed prior to
the Mine Abandonment Act which has
required abandonment plans to be
deposited with an appropriate authority
since 1872.
1805
1847
1998
Geophysical image of mineshaft noted on historic (1805 and 1847) geological maps.
30
Source: British Geological Survey archives
eological maps, although
providing details of industrial
activity over long periods, are
unable to account for all geohazards associated with mineral abstraction. A recent investigation, to identify
the location of concealed mine shafts
prior to construction works, illustrates
the growth and decline of mining
activity within the Lancashire coalfield.
A non-intrusive geophysical investigation located subsurface features associated with mine shaft locations, by
mapping ground conductivity. The
surveys confirmed both the location and
the integrity of mine shaft capping.
Having identified these geohazards,
contingency plans could be formulated
for their avoidance.
Paul Tod © BGS, NERC
. . . Newsline . . . Newsline . . . Newsline . . .
Professor Jane Plant CBE.
BGS scientists receive awards
Professor Jane Plant CBE, Assistant
Director of the Minerals, Environment
and Geochemical Surveys Division of the
BGS, is to be presented with the Lord
Lloyd of Kilgerran prize for 1999 by the
Foundation for Science and Technology
in September. The prize has been
awarded ‘for the application of fundamental geochemical modelling and sound
observation in the development of
simple, cost-effective methods of minimising the impact of contamination on
the environment and particularly human
health’. The Foundation’s Council note
that Prof. Plant’s work ‘has already
reaped many benefits both in the UK and
in the developing world’. This prestigious
prize has previously been awarded to,
among other notable scientists, Professor
Ian Wilmut of the Roslin Institute, for his
work in cloning Dolly the sheep, and Dr
Tim Berners-Lee OBE, the inventor of
the World Wide Web.
Conference report – Isotopes
in Palaeoclimate Research
■ Isotopes in speleothems — Dr Frank
McDermott — (University College
Dublin).
The Natural Environmental Research
Council (NERC) has identified Global
Change as one of the five main issues
on which its research should be focused
in the next five to ten years, and the
need to know about natural climate
variation over a range of timescales is
regarded as a key area for development.
Since isotopic techniques are likely to
continue to play an important role in
gaining this knowledge, the NERC
Isotope Geosciences Laboratory
(NIGL) organised a forum where the
future applications of isotopic methods
in palaeoclimate research could be
discussed. The forum, held on
Wednesday 28th April 1999 at
Leicester University, comprised the
following seven keynote lectures:
■ Isotopes in Polar ice-cores —
Dr David Peel (British Antarctic
Survey).
■ Stable isotopes in Quaternary
palaeoclimate research — Prof.
Neil Roberts (Plymouth University).
For copies of the conference proceedings or other information contact
■ Isotopes in the marine environment
— Prof. Nicholas Shackleton
(Cambridge University).
■ Isotopes in the lacustrine environment — Prof. Alayne Street-Perrott
(University of Wales, Swansea).
■ Isotopes in dendroclimatology —
Prof. Mark Pollard (Bradford
University).
■ PAGES — The PAst Global
changES initiative — Prof. Frank
Oldfield and Prof. Tom Edwards.
The forum was attended by over 250
delegates from universities and research
institutes in Britain, as well as many
from overseas. The NIGL (part of the
BGS) is a central facility for providing
isotopic scientific support to the UK’s
environmental research community.
Dr Melanie Leng, NERC Isotope
Geosciences Laboratory,
BGS Keyworth
Tel: 0115 9363515
e-mail: [email protected].
The NIGL webpage address is: http://
www.bgs.ac.uk/bgs/w3/nigl/index.htm.
The Geological Society of London has
awarded The William Smith Fund to Dr
Simon Young for ‘leadership and devotion
to duty as the lead BGS volcanologist
during the recent Montserrat eruption, and
for its subsequent documentation’.
Dr Stephen Horseman of the Fluid
Processes and Waste Management
Group has received an Individual
Special Merit promotion in recognition
of his research activities on water, gas
and solute movement in clay-rich
materials. Dr Horseman, who is a longstanding member of the OECD Nuclear
Energy Agency SEDE Working Group
on Groundwater Flow in Argillaceous
Rocks, will lead a team of scientists
studying the role of clay–water interaction in the transport properties and
behaviour of shales and mudrocks.
From l to r. Prof. R. Parrish (head of NIGL/Leicester University), Prof. T. Edwards (ISOMAP
director - PAGES), Prof. M. Pollard (Bradford University), Prof. Sir N. Shackleton (Cambridge
University), Dr M. Leng (NIGL), Prof. N.Roberts (Plymouth University), Dr D. Peel (BAS),
Prof. A. Street-Perrott (University of Wales, Swansea), Prof. J. Beeby (Pro Vice Chancellor,
Leicester University), Prof. F. Oldfield (exective director of PAGES), Dr F. McDermott
(University College Dublin).
31
. . . Newsline . . . Newsline . . . Newsline . . .
The meeting was attended by more than
100 delegates, with representatives from
regulatory authorities, the water and
chemical industries, consultants, research
and academic institutions and the legal profession. The European context was emphasised by the presence of speakers and
delegates from UK, Denmark, Sweden,
Belgium, Netherlands, Spain, Germany,
Ireland, Finland and Austria. Groundwater
quantity and quality issues were discussed
from both a scientific perspective and
within the regulatory framework.
HORSA project wins DTI
LINK support
Peter Kilfoyle MP looks on as Dr David Falvey, Director of the BGS, signs the agreement with
the Ordnance Survey at the Royal Observatory in Greenwich.
BGS signs ‘on the line’
The BGS, along with eight other public
bodies and agencies, has signed an
agreement with the national mapping
agency, Ordnance Survey. The consortium
will have access to consistent computer
mapping and geographical information that
can be related to the members’ own data.
Around 80 per cent of all information
gathered in Britain has some geographical
element, so the potential for linking
different sets of information to a common
framework is enormous.
different parts of government, both central
and local, by giving staff better access to
information and making it much easier for
different parts of government to work in
partnership with one another.’
The other first-wave signatories are the
Department of the Environment,
Transport and the Regions; Ministry of
Agriculture, Fisheries and Food; Office
of National Statistics; Welsh Office;
Environment Agency; Forestry
Commission; English Heritage; and
English Nature.
‘In our Modernising Government White
Paper we have set out the importance of
improving connections between the
Mr Kilfoyle said it was apt that the signing
took place on the Prime Meridian at
Greenwich, where the new millennium will
officially start. ‘It certainly gives real
meaning to the phrase “signing on the
line”—and it also helps focus our minds on
where government services are heading as
we approach the twenty-first century.’
Groundwater in tomorrow’s
Europe
Geological Society, the core members of
the UK Groundwater Forum,
EuroGeoSurveys and EUREAU.
The British Chapter of the International
Association of Hydrogeologists held a
seminar entitled ‘Groundwater in
tomorrow’s Europe—developments at
the regulatory–scientific interface’ in
Nottingham on 16–17 May 1999. The
meeting was co-sponsored by the
Hydrogeological Group of the
The objectives of the event were: to
provide a professional update for groundwater professionals, a forum for informed
debate on groundwater resources and
quality in the European context, and to
produce a ‘consensus’ report reflecting
current thinking in the groundwater
community.
Cabinet Office Public Service Minister,
Peter Kilfoyle MP, backed the initiative
as the agreement was being signed at the
Royal Observatory in Greenwich.
32
A DTI LINK award under the Sensor
and Sensor Systems for Industrial
Applications programme has been won
by the BGS in conjunction with Soil
Mechanics and Charnvel Ltd. The
project is due to start in September 1999
and will last for 30 months.
The project is HORSA (Horizontally
polarised shear wave source for site
characterisation) and it will develop a
new technology for environmental and
civil engineering investigations.
The new equipment will augment the
existing range of compressional and vertically polarised shear wave equipment manufactured by the BGS and will provide a
powerful survey tool for formation type
evaluation. It will speed up the taking of
measurements, in line with the recommendations of the Egan Report to reduce the
cost of engineering projects over the next
five years.
For further information contact:
Steve Shedlock,
Fluid Processes and Waste
Management Group, BGS Keyworth,
Tel: 0115 9363258,
Fax: 0115 9363261.
Cleaning up our act
The BGS is improving its environmental
performance and ensuring mandatory
environmental requirements are met
through the introduction of an
Environmental Management System.
The Chartered Institute of Building
Services Engineers believe that energy
efficiency measures could save up to
30% of an organisation’s existing energy
. . . Newsline . . . Newsline . . . Newsline . . .
consumption. The BGS’s Edinburgh
office, Murchison House, is leading the
way in this area, as it now has the benefit
of double-glazing throughout the
building. Passive infra-red controls are
fitted in corridors and toilets to control
the lighting and all twin light fittings have
been converted to single fittings.
Individual room temperature controls are
being installed in every office.
New lamps for old
making your own earthquake, testing the
‘rock doctor’, looking at photographs in
stereo, and cracking fossiliferous rock
core. This year’s Open Day will build on
previous Open Days and include a range
of new exhibits.
The DTI Core Store in Gilmerton Road,
Edinburgh will also be holding an Open
Day during the same hours and there
will be a complimentary bus service
operating between Murchison House
and the Core Store.
At Keyworth, a new energy-efficient
boiler system for the site was recently
installed, there is an ongoing programme
to replace old fluorescent tubes with
energy-efficient ones and double-glazing
is being installed on a block-by-block
basis. With the paper and cardboard
recycling initiative at Keyworth, we now
have an efficient recycling system in
place, saving the BGS almost £9000 per
annum in waste disposal costs.
Looking to the future, we are considering
installing a combined heat and power
system in one of our blocks, which would
reuse much of the energy consumed there.
We will also be examining the possibility
of using alternatively-fuelled vehicles in
the BGS fleet.
For more information contact:
Adrian Cooke, Environment
Management Adviser.
BGS Keyworth
Tel: 0115 9363159
BGS open day, Edinburgh
Murchison House, the Edinburgh office of
the BGS is opening its doors to the general
public on Saturday 11 September between
10am and 5pm. The Open Day is part of
Scottish Geology Week and admission is
free. The previous Open Day in 1998
attracted over 500 visitors of all ages and
backgrounds. Interested amateur geologists, schoolchildren (of all ages), in fact
anyone with an interest in their environment is welcome to attend.
The main aim of the Open Day is to communicate the work of the BGS to the
general public and to increase awareness
of important geoscientific issues. There
will be hundreds of ‘hands on’ and
computer-generated displays and exhibits,
rock, mineral and fossil collections, activities and quizzes. Highlights of previous
Open Days include: panning for ‘gold’,
Gemmology: ‘Lily-pads’ – a typical inclusion
in peridot as seen through a microscope.
BGS and ILEX Technologies
sign joint working agreement
The BGS and ILEX Technologies Ltd
have signed a Memorandum of
Understanding enabling them to work
together on projects, principally in the
international oil and gas markets.
The fossil collection has always proven to be
a star attraction at BGS Open Days.
A selection of core will be on display to
the public, illustrating various aspects of
the geology of oil and gas, including:
■ Oil-bearing sandstones and conglomerates from the South Brae
Oilfield and samples of Kimmeridge
Clay, the source of much of Britain’s
oil
■ Gas source rocks and reservoir sandstones (river deposits) from the
Murdoch Gasfield and aeolian dune
reservoir sandstones from the Leman
Gasfield
■ Sealing or cap rocks (rock salt) from
the Southern Gas Basin
■ Volcanic ash beds, beach sands, fossil
shells and plants, fossil soils, and core
across the Cretaceous– Tertiary
boundary will also be displayed
In addition, videos will be shown
explaining how rocks provide many of
the essentials for everyday living,
including gas from the North Sea.
For more information contact:
BGS Murchison House,
Tel: 0131 667 1000
DTI Core Store, Tel: 0131 664 7330
33
This partnership brings together the
world’s longest established national geological survey with a newly-formed high
technology company based in Sussex.
David Ovadia, the BGS’s Business
Development Manager, said
‘BGS has extensive assets of data,
expertise and a history of working in over
100 countries. Whilst our core business is
public good science, the partnership with
ILEX creates a synergy between science
and business that will ultimately benefit
the UK economy. We are looking forward
to working with ILEX.’
Mario Cataldo, Managing Director of
ILEX, said
‘We have long recognised the enormous
skills and experience within the BGS. Our
partnership with them opens up many new
opportunities for both of us. Our clients
will benefit from ILEX’s business focus
and the BGS’s world class reputation.’
ILEX supports strategic PC-based exploration and production applications, and the
IT and Data Management environment
within which these applications operate, for
oil and gas companies that no longer have
the in-house expertise, time or resources to
manage these important functions.
For further details contact:
David Ovadia,
Business Development Manager,
BGS Keyworth
Tel: 0115 936 3392
Fax 0115 936 3150
Vicky Hards © BGS, NERC
Vicky Hards © BGS, NERC
. . . Newsline . . . Newsline . . . Newsline . . .
Above: An example of Shan Wareham’s art: the BGS’s rock and mineral collections proved a
rich source of inspiration. Right: The artist at work in the BGS Core Store at Keyworth.
The BGS petrological
collections in art
The BGS’s petrological collections,
specifically samples from the Museum
Reserve and Mineral Reference collection, were recently put to a novel use as
subjects for the work of a young artist,
Shan Wareham. Shan is currently in the
final year of a GNVQ course in art and
design at South Nottingham College, and
the pieces she produced during her recent
visit to the BGS at Keyworth will form
part of the final show at the end of her
course. She was originally inspired by the
wealth of colours, shapes and textures
occurring naturally in rocks and minerals,
and her work captures beautifully, in a
slightly abstract form, some of the
essence of these.
The BGS petrological collections are kept
both for reference and as a resource for
future investigations. They have few
rivals in providing the basis for detailed
petrology studies and characterisation of
the UK landmass, and represent the solid
evidence for the BGS's maps and many
historic geological discoveries. Outcrop
material from all parts of the country is
supplemented by samples from boreholes
and quarries. Many of the sites are no
longer accessible.
Use of the petrological collections both
in scientific research and other applications is encouraged, enquiries are
welcome and material may be examined
at the BGS’s offices or loans arranged.
For more information contact:
Vicky Hards, BGS Keyworth
Tel: 0115 9363336
Fax: 0115 9363352
On the 3rd July 1999 a unique visitor
attraction was opened in Edinburgh by
HM The Queen. Our Dynamic Earth
has firm roots in the landscape and
history of Edinburgh. Situated at the
foot of Arthur's Seat, at the end of the
crag and tail feature stretching from
Edinburgh Castle to the Palace of
Holyroodhouse and just a few hundred
metres from where James Hutton, the
Father of Modern Geology, wrote his
Theory of the Earth, Dynamic Earth
takes a holistic view of the planet
Earth, exploring how it was formed
and the diversity of environments that
have been produced. BGS geologist,
Dr Stuart Monro, has been on secondment to Dynamic Earth as its
Scientific Director and was responsible
for co-ordinating the scientific story.
© Dan Tuffs
Our Dynamic Earth
HM The Queen visiting the Dynamic Earth exhibition earlier this year.
34
MSc COURSE
COMPUTING FOR GEOSCIENCE
New International
Geochemical datasets on CD-ROM
This one-year MSc, awarded by Nottingham Trent University, is
taught jointly by the University’s Department of Computing and the
British Geological Survey. Both organisations are in Nottingham.
The BGS announces the release of a new series of
CD-ROMs providing International Geochemical datasets
for sale under licence.
Objective
To develop hybrid skills in geoscience computing through
specialised hands-on problem-solving skills applied to
geoscientific work. The course is for practising geoscientists, and is designed to meet the modern needs for information technology in the earth sciences.
Regional Geochemical Data are now available on CDs
for major BGS projects in the following countries:
• Indonesia (Sumatra)
Content
The course has two parts: a modular course followed by an
individual, stand-alone project. The modular, taught course
comprises three themes, Geoscience, Computing and
Application Tasks. The latter tasks form the backbone of the
course and unite both the geoscience and computing themes in
a series of hands-on assignments and activities. During the
final project, students will have the opportunity to work on
data in one of the world’s foremost geological surveys.
• Zimbabwe (NE Zimbabwe & Harare)
Entry
Candidates must have a good honours degree or equivalent
experience in one of the following areas:
• Geoscience • Civil Engineering • Surveying
• Pure Sciences • Combined Sciences
For further information, prices and order-form, visit our
web site: www.bgs.ac.uk/geochemCD.
GEOLOGY
Further information from:
Dr I E Penn, Training Co-ordinator, British Geological Survey,
Keyworth, Nottingham, NG12 5GG, UK
Telephone: +44 (0)115 936 3187 Fax: +44 (0)115 936 3604
e-mail: [email protected]
• Bolivia (Proyecto Precambrio)
• Peru (Northern Peru – Cajamarca Belt)
• Kenya (Samburu-Marsabit)
Dr J W Baldock, Analytical and Regional
Geochemistry Group,
British Geological Survey,
Keyworth, Nottingham, NG12 5GG,UK
Tel: +44 (0) 115 936 3500
Fax: +44 (0) 115 936 3329
e-mail: [email protected]
British
Geological
Survey
Shaping the landscape
The landscape and scenery are closely related to the underlying geology
and different types of rock and fossil tell us about the past history of the
Earth. Find out more about this fascinating subject from our books, guides
and maps.
Suitable for professional and amateur geologists, students of geology of all
ages, walkers, climbers, tourists and everyone interested in local and
natural history.
Available from booksellers or contact the British Geological Survey for
further information or a free catalogue:
Sales Desk,
British Geological Survey,
Keyworth, Nottingham, NG12 5GG
Tel: +44 (0) 115 936 3241
Fax: +44 (0)115 936 3488
e-mail: [email protected]
Please quote Earthwise when placing orders
British
Geological
Survey
British
Geological
Survey
Principal offices
of the
British Geological
Survey
Kingsley Dunham
Centre, Keyworth,
Nottingham,
NG12 5GG
= 0115–936 3100
Murchison House,
West Mains Road,
Edinburgh EH9 3LA
= 0131–667 1000
Maclean Building,
Crowmarsh Gifford,
Wallingford, Oxfordshire
OX10 8BB
= 01491–838800
London Information Office
at the
Natural History Museum
Earth Galleries,
Exhibition Road
London SW7 2DE
= 0171–589 4090
St Just,
30 Pennsylvania Road,
Exeter EX4 6BX
= 01392–78312
Geological Survey of
Northern Ireland,
20 College Gardens, Belfast
BT9 6BS
= 01232–666595
ISSN 0967-9669
The British Geological Survey is the national geological survey of
the United Kingdom. Its primary function is to maintain and continuously revise geological information for the land and offshore
areas of the United Kingdom. Its expertise is available for projects
with government departments, industry or academia, within the
United Kingdom and internationally.
The BGS staff cover a very wide range of geoscience and related
disciplines, so its services can be tailored to the specific needs of
clients. The coordination of effort by multidisciplinary teams is a
speciality and results in fully integrated packages. Where in-house
expertise is not available, the BGS is able quickly to identify and
appoint appropriate experts through its worldwide contacts.
As a respected member of the international geoscientific
community, the BGS has successfully collaborated on projects
with other organisations in more than 90 countries, and individual BGS scientists maintain close links with specialist coworkers around the world. Techniques in all of its activities are
thus constantly reviewed and improved. In-house training programmes enable staff to keep abreast of new thought and
methods in geoscience.
If you are planning a project in geoscience, the BGS may be
able to help. For further details please contact the Head of
UK Business Development. Tel: 0115 936 3392; Fax: 0115
936 3150; email: [email protected]
For information on the whole range of the BGS’s activities visit
the BGS website: www.bgs.ac.uk
Published by:
British Geological Survey
Editor:
David Bailey
Design:
Adrian Minks
Print Production:
John Stevenson
Printed by:
Hawthornes, Palm Street, New Basford,
Nottingham NG7 7HT
The BRITISH GEOLOGICAL SURVEY is a
component body of the NATURAL
ENVIRONMENT RESEARCH COUNCIL
© NERC 1999