Science
and
Tourism
Geology of
buildings
in Leeds
Introduction
Time
This walk through the geology of Leeds should take no more
than 1.5 hours, although it could be longer if you take in
some shopping, the Art Gallery or stop for a coffee or lunch
en route. It is a circular walk designed so you can pick it up
at any point or perhaps look at only part of it.
Background
2007 marked the 800th anniversary of the foundation of
Leeds as a borough. This geological walk round the buildings
of the city centre offers a chance to look at the history of the
Earth through the materials used to build the city. Leeds is
built on the Carboniferous (360-290 million years old) Coal
Measures and Millstone Grit. The sandstones from these
have provided building stones and the clays have been used
for making bricks, terracotta and decorative tiles. Leeds is
on the northern edge of the Yorkshire coalfields which gave
easy access to cheap coal and iron during the Industrial
Revolution. This led to the rapid growth of foundries,
engineering works and new building in the city. With the
coming of the railways, building stones were brought in from
further afield (eg. Scottish granite). The twentieth century
saw the development of steel framed concrete buildings.
These use stone, sourced from round the world, as a
decorative cladding. This walk will give you an insight into
the geology behind the rocks used to build Leeds.
The Rocks
Igneous Rocks
Igneous rocks have crystallised from molten rock known as
magma and are formed of interlocking crystals. If the
magma cooled quickly the crystals are very small (finegrained); if it cooled slowly the crystals are larger (coarsegrained) and can be seen with the naked eye. The different
types of minerals in igneous rocks give the rocks their
distinctive appearances.
Granite
Granites are coarse-grained igneous rocks which have cooled
deep (1.5-50km) in the Earth’s crust. They are used in a
more decorative than functional way and can be seen as
building facades, pillars, plinths and in paving. Granites are
composed of three main minerals: quartz (white to clear
crystals), alkali feldspars (often pink) and plagioclase
feldspar (shades of grey). The colour of building stone varies
depending on the proportions of each mineral from pink
(Shap, Rose Perrion (Italian) and Peterhead granites) to grey
(Hantergantick granite from Bodmin, Cornwall) to blue-grey
(Rubislaw granite). The coarse grained Larvikite is easily
mistaken for granite. However, it contains virtually no quartz.
It has a distinctive blue-grey appearance due to the
presence of large crystals of plagioclase feldspar.
Granodiorite
Granodiorite is similar to granite, but has a greater portion of
darker coloured crystals (plagioclase feldspar) which give it a
darker appearance. The Verde Prairi Granodiorite is dark
green and the finer-grained Bon Accord (from South Africa)
is black.
Images of the types of rocks found in Leeds
Millstone Grit
Portland Stone
Shap Granite
Larvikite
Sedimentary Rocks
Sedimentary rocks are formed when older rocks are worn down
and transported by wind and water and the pebbles, grains of
sand, silt or mud from these old rocks are deposited again in
layers. Limestones are formed in a similar way when the
remains of tiny sea creatures settle on the sea bed and are
broken up. New layers of sediments bury and compress older
layers squeezing out the water and cementing them together
into rocks. Sediments are laid down in many different
environments including rivers, lakes, oceans and deserts.
Sandstone
Millstone Grit (333-315 million years ago) and the Coal
Measures (300 million years ago)
The Millstone Grit is a medium - to coarse-grained sandstone.
It can contain large white pebbles of quartz, some of which
may have been transported from as far away as Scotland. It
was deposited in the channels of a large delta system similar
to the Mississippi delta today. The Coal Measures consist of
fine-grained sandstones, shales and coal seams. They were
deposited at a time when Yorkshire lay close to the equator
and the delta system of the Millstone Grit had given way to
vast swampy forests of tree ferns and giant mosses. As plants
died, they were buried and compressed and eventually
formed the coal layers seen today.
Limestone
Portland Stone (200 million years ago) and Oolitic
Limestone (Ketton & Bath Stone 200 million years ago)
The Portland Stone is a white limestone which often
contains many fossils. It is quarried on the Isle of Portland,
Dorset. The Oolitic Limestone is a buff-coloured rock
composed of tiny spheres of concentric layers of calcium
carbonate. These spheres are known as ooliths. Both
limestones were deposited in warm, shallow, tropical seas.
Metamorphic Rocks
Metamorphic rocks form when igneous or sedimentary rocks
experience high temperatures and pressures as they become
deeply buried in the Earth and/or were caught up in
continental collisions. The rocks are exposed to high enough
temperatures to change the crystals or grains within them,
but not high enough to melt them.
Marble
Marble is recrystallised or metamorphosed limestone. Fossils
are often preserved, making this an ornate building stone.
Time Line
The time line shows key events in the history of the Earth
and their links to Leeds. The figures on the left give the time
of these events as if the age of life on Earth were
compressed into a year.
18 SECS AGO
2 MINS
35 MINS
2.5 HOURS
5 HOURS
LEEDS CITY FOUNDED
1,000 years
NEOLITHIC AGE
6,000 years
HIPPOS LIVE IN LEEDS
120,000 years
NEANDERTHAL MAN
0.5 million years
START OF LAST ICE AGE
1 million years
20 HOURS
OLDEST HUMANOIDS - AUSTROPITHICUS
11.5 DAYS
EARLIEST PRIMATES
14 DAYS
1 MONTH
4 million years
55 million years
METEORITE HIT - DINOSAURS GO EXTINCT
65 million years
FORMATION OF PORTLAND STONE
145 million years ago
1.1 MONTHS
FIRST BIRD - ARCHAEOPTERYX
1.6 MONTHS
FIRST DINOSAUR - EORAPTOR
1.7 MONTHS
CLIMATE CHANGE &
GREATEST MASS EXTINCTION
155 million years
228 million years
250 million years
2.1 MONTHS
FORMATION OF COAL MEASURES
2.2 MONTHS
FORMATION OF MILLSTONE GRIT
2.9 MONTHS
FIRST LAND ANIMALS
3.6 MONTHS
FIRST VERTEBRATES
4.6 MONTHS
OLDEST JELLY FISH
1 YEAR
300 million years
315 million years
420 million years
530 million years
670 million years
OLDEST SINGLE CELL LIFE
1750 million years
Fast Facts
• Some of the building stones used in Leeds come from as
far away as South Africa (Bon Accord in the Victoria
Quarter) and China (the granite plinths in City Square).
• The outlines of large coiled ammonites can be seen on the
base and pilaster of a column in the Victoria Quarter.
• Portland Stone has been used in the construction of
famous buildings including Buckingham Palace, St Paul’s
Cathedral and the Cenotaph.
• Leeds Cathedral replaces the 1838 building which was
located at the intersection of Cookridge Street and the
Headrow. It was demolished to allow for street widening.
• Holy Trinity Church was built on the site where travelling
theatres, circuses and the Leeds Fair were held.
Information
For more details on the building stones of Leeds
and other Science and Tourism projects go to
http://www.see.leeds.ac.uk/scienceandtourism
Other websites of interest
http://wwwleedsgeolassoc.freeserve.co.uk
Acknowledgements
Francis G Dimes & Murray Mitchell, ‘The Building and
Stone Heritage of Leeds’. The Leeds Philosophical and
Literacy Society of Leeds, Second Edition, 2006.
Alternative
formats are
available from
0113 343 3929
The Science and Tourism Project
University of Leeds
Leeds LS2 9JT
e [email protected]
w www.see.leeds.ac.uk/scienceandtourism