UNIVERSITY OF GOTHENBURG
Department of Earth Sciences
Geovetarcentrum/Earth Science Centre
Morphologic characterization of stream-lined
landforms shown on the new LiDAR elevation
database in Sweden and the relationship
between their orientation
and the SGU striation database
Helena Lindhage
ISSN 1400-3821
Mailing address
Geovetarcentrum
S 405 30 Göteborg
Address
Geovetarcentrum
Guldhedsgatan 5A
B641
Bachelor of Science thesis
Göteborg 2011
Telephone
031-786 19 56
Telefax
031-786 19 86
Geovetarcentrum
Göteborg University
S-405 30 Göteborg
SWEDEN
Abstract
A new high resolution elevation map of Sweden, measured by LiDAR-technology (Light
detection and ranging), makes it possible to see landforms that not have been detected before.
The objective in this paper has the focus on the stream-lined landforms, which are clearly
visible on the new elevation map. The stream-lined landforms show the latest ice movement
orientation of the inland ice. The investigated area is a part of southernmost Sweden.
Directions of previously mapped striations are compared with the orientations of the streamlined landforms. The direction of the striations and the landforms correspond mostly well but
in some areas not so well. It is possible to see which of the striations being related to the latest
ice-movement since their direction are parallel with the orientation of the stream-lined
landforms. The lengths of the stream-lined landforms are calculated, and compared with a
classification of stream-lined landforms (Bennett and Glasser, 2009). The comparison shows
that most of the stream-lined landforms have the same length as drumlins and mega-flutes. In
ArcGIS a small area with stream-lined landforms is analyzed to visualize examples of their
appearance. A soil classification map shows that some of the stream-lined landforms have
bedrock outcrop in the interpreted proximal part. Profiles show that the investigated streamlined landforms along the length axis have a steep proximal part and a flatter distal part. At
the distal part, some landforms are flattening out to approximately the same angle as the land
surface.
Keywords: LiDAR; stream-lined landforms; drumlin; striae; GIS-analysis
Sammanfattning
En ny högupplöst höjdkarta över Sverige, mätt med LiDAR-teknik (Light detection and
ranging), gör det möjligt att se landskapsformer som tidigare inte kunnat ses. En målsättning
med arbetet är att kartlägga de strömlinjeformade kullarna, som tydligt kan ses på höjdkartan.
Kullarna visar orienteringen av den senaste inlandsisens rörelse. Ett område i sydsverige har
undersökts. Riktningen av tidigare kartlagda isräfflor jämförs med orienteringen av de
strömlinjeformade kullarna. Räfflornas och kullarnas riktningar överensstämmer till stor del,
men i vissa områden förekommer skilda riktningar. Det är möjligt att se vilka av isräfflorna
som är relaterade till den senaste isrörelsen då räfflornas riktingar är parallella med kullarnas
orientering. Längden av de strömlinjeformade kullarna har beräknats. En jämförelse med en
klassificering av strömlinjeformade kullar (Bennett och Glasser, 2009) visar att dessa kan
betecknas som drumliner och mega-flutes. I ArcGIS gjordes även analysen av ett mindre
område med strömlinjeformade kullar för att få ett exempel på hur geomorfologin ser ut. En
jordartskarta visar att vissa av de strömlinjeformade kullarna har berg i dagen i de proximala
delarna. Profiler visar att de undersökta kullarnas form längs längdaxeln är brant i den
proximala delen och har en svag lutande distal del där kullen planar ut till samma lutning som
markytan.
Nyckelord: LiDAR; strömlinjeformade kullar; drumlin; isrörelseriktning; isräfflor; GISanalys
Table of contents
Introduction ............................................................................................................................................. 1
Background ............................................................................................................................................. 1
New elevation database ....................................................................................................................... 1
Investigated area .................................................................................................................................. 2
Stream-lined landforms and subglacial conditions.............................................................................. 3
Glacial striations .................................................................................................................................. 4
Stream-lined landforms vs. glacial striations .......................................................................................... 6
Method ................................................................................................................................................ 6
Result................................................................................................................................................... 8
Discussion ......................................................................................................................................... 10
Metrics of stream-lined landforms ........................................................................................................ 12
Method .............................................................................................................................................. 12
Result................................................................................................................................................. 13
Discussion ......................................................................................................................................... 18
Conclusions ........................................................................................................................................... 18
Further studies ....................................................................................................................................... 19
Acknowledgments ................................................................................................................................. 19
References ............................................................................................................................................. 19
Introduction
A new high resolution elevation model, measured by LiDAR, provides a new view of the
geomorphology of Sweden. The model allows us to see landforms that are unable to be
detected in aerial photographs, satellite images, by fieldwork or in earlier topographic maps
and digital elevation models. Additionally, well-known landforms are shown in even greater
detail.
The landscape is affected and to a high degree formed by the inland ice. Glaciations have
formed stream-lined landforms such as drumlins and mega-flutes that are clearly visible in the
elevation model. These stream-lined features are composed predominantly of till and they are
interpreted to show the latest ice-flow direction.
Ice-flow directions in Sweden are usually estimated during mapping by looking at directions
of glacial striations, drumlins, and other glacial landforms, and till fabrics. With the high
resolute elevation model we can get a clearer view of the direction of the latest ice movement
in Sweden. The purpose of this paper is to compare orientation of the stream-lined landforms
with the direction of mapped striations from the Geological Survey of Sweden (SGU), which
allows us to interpret sets of striations that not are parallel to the stream-lined forms as being
produced during earlier phases of glaciation. Metrics of stream-lined landforms are
investigated for an area to show an example of the landforms appearance.
Mapping the orientation of glacial stream-lined landforms in Sweden is an important part of
understanding the subglacial conditions of the latest ice advance and can allow us to better
reconstruct paleoglaceological environments. It is important to learn more about stream-lined
landforms to get a better understanding of how, and during what conditions subglacial
landforms are created.
Background
New elevation database
The Swedish mapping, cadastral and land registration authority (Lantmäteriet) has started to
make a new elevation database with high resolution. The database will cover the whole area
of Sweden, in purpose to predict, and be prepared for the impact of future climate changes
(Morville and Burman, 2011). To generate the elevation model, LiDAR (light detection and
ranging) is used. LiDAR is an airborne scanning technique using laser pulses to measure the
distance between the ground and an airplane. These measurements are then modified to
exclude vegetation, buildings and roads. The generated map shows the topography of the land
surface. The elevation model has a 0,2 m resolution and a pixel size of 2 x 2 m. The
measurements are currently in progress, and for now, only a small area of Sweden is finished
and collected in the database.
1
Investigated area
Glacial stream-lined landforms were mapped in the southern part of Sweden where data from
the database is available, figure 1 (left). The landforms in this area were mapped to determine
the latest ice-movement direction, and their orientations are compared to the direction of
glacial striations. A small area is selected to present a close-up example of the geological and
geomorphologic characteristics of an area with stream-lined landforms, figure 1 (right). This
area was selected because several stream-lined landforms are visible.
Figure 1. Left: The investigated area in southern Sweden is defined by the red rectangle. The filled
coloured areas represent the areas for where the LiDAR-measurements have been done so far.
Right: The location of the small area where geomorphologic and geologic characterisation of stream-lined
landforms are investigated.
2
Stream-lined landforms and subglacial conditions
The LiDAR elevation data map shows stream-lined geomorphologic landforms that are
clearly lined up parallel to the direction of the ice-flow (fig. 2), as indicated by striations and
other features. Although some of the stream-lined landforms in the investigated area have
already been identified, the LiDAR images reveal many stream-lined landforms never seen
before.
Figure 2. Examples of how the stream-lined landforms are visible in the elevation data map, measured by
LiDAR-technique. The positions of the examples are shown in the map in the lower right corner.
3
Stream-lined landforms may be classified into different categories according to size and shape
(Clark 1993). Glacial stream-lined landforms include drumlins, flutes, mega-flutes, and mega
scale glacial lineations (MSGL).
Drumlins are oval shaped and stream-lined, often with an internal composition of glacial drift
and with a length of 10–3000 m (Bennett and Glasser, 1998). Drumlins have been widely
investigated and written about in scientific articles (Stokes, Spagnolo and Clark, 2011).
Flutes are stream-lined landforms which are smaller than drumlins and they usually starts
with an obstacle in the proximal end. According to Bennett and Glasser (1998) flutes not
often exceed a length of 100 m. What characterizes flutes is the constant shape in crosssection. Mega-flutes differ from flutes in the way that they often exceed a length of 100 m and
often lack an obstacle in the proximal end. MSGL are long and big in size and exceed 8 km in
length and are 200–1300 m wide (Ben and Evans, 1998). All the above mentioned landforms
have internal compositions that consist of glacial sediment.
Many suggestions have been made about how stream-lined landforms are formed. There is no
theory that alone explains the formation of all the different types of stream-lined features
(Benn and Evans, 1998). Commonly accepted is the theory that the stream-lined landforms
are produced both by subglacial erosion and/or deposition (Bennett and Glasser, 2009). Clark
(1993), suggest that stream-lined landforms are created subglacially either abrupt in high
velocity and/or during a long period of time with constant glacial conditions. Enough glacial
debris must be present for the stream-lined landforms to be created. One of the most accepted
theories of drumlin formation is Boultons (1987) theory that the sediment-bed undergoes
erosion and redistribution in deforming layers. His suggestion is that the drainage ability of
different coarse sediments makes a difference in the beds resistance of deformation. An area
with finer grained sediment is not so good drained as an area with coarser grains, which
makes the fine grained area weaker and makes it move faster than the coarse-grained. It is the
coarser grained sediment that is the core of drumlins.
Glacial striations
The Geological Survey of Sweden (SGU) has measured and mapped glacial striations since
geological mapping started in 1858. Striations represent different events of ice-movement
during the latest glaciation but may also include earlier glaciations. Striations can also be
produced both during ice retreat as well as ice advance (Bennett and Glasser, 2009).
At SGU the striations are gathered in a database that includes more than 60 000 observations
for the whole area of Sweden. Figure 3, shows a map of the striations of the investigated area.
The striation database includes location, bearing, and interpreted relative age. The mapped
directions of the striations are rounded off to whole 5 degree digits (Rudmark, 2009). The
relative age of striations is hard to determine, but can be done in a few instances by looking at
how striae cross or where older striae are present in lee side positions.
4
Figure 3. Map of striations from the Geological Survey of Sweden (SGU) database.
5
Stream-lined landforms vs. glacial striations
Method
GIS analysis
Geographical information system ArcGIS 10 was used for analyzing the elevation data.
Stream-lined landforms where identified visually by studying the elevation map using a scale
between 1:30 000-1:60 000. The identified stream-lined landforms are recognized as elongate,
straight, unbroken hills or ridges. In the ice-movement direction analysis no dividing into
categories has been made to separate different types of stream-lined elongated
geomorphologic landforms since all these show the orientation of the ice-flow. The oriented
stream-lined landforms are interpreted to have the same direction as the SGUs striation model
in figure 3, with a general direction from north to south. The directions of the stream-lined
landforms are, when no striations are present, interpreted by visually studying the map.
In ArcGIS the axial directions of the stream-lined landforms are manually drawn by using
polylines, (see the example in figure 4). The axial directions of the stream-lined landforms are
compared with mapped striations. To do this comparison, I divided the area of interest into
equally sized squares, by using predefined index squares 10 x 10 km of the coordinate system
SWEREF99 TM. A polygon for each 10 x 10 km is drawn to be able to define the 10 x 10 km
areas. For each square the mean direction of the stream-lined landforms is calculates by using
Linear directional mean in Spatial statistic tool.
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Figure 4. Lines for each of the visual stream-lined landforms are drawn manually in ArcGIS.
Directions of the glacial striations are as for the stream-lined landforms extracted for each 10
x 10 km square. In some areas, the striations have 2-3 different sets of directions. The
directions that did match the mean directions of the steam-lined landforms were sorted out by
using Windows Excel. Mean directions for the striations where then calculated. When the
striations are measured and mapped by SGU the directions are rounded off to whole 5 degree
digits. I chose not to round off the measured direction of the stream-lined landforms in
purpose to get a more exact direction. The round off in measured striations may have affected
the result.
7
In squares without stream-lined landforms mean values for the striations were not calculated.
The directions of the striae that did not match the axial direction of the landforms are
interpreted to be of older age than the stream-lined landforms. No further investigation has
been done with these deviated sets of striae-directions.
Result
The mean directions of the stream-lined landforms and the striae for areas of 10 x 10 km are
shown in figure 5. The directions of the stream-lined landforms are essentially the same as
those of the striations over the entire investigated area, although in some areas the directions
differ. An interpretation of the ice movement direction displayed with flow lines is shown in
figure 6.
8
Figure 5. The mean directions of striations are shown with black arrows and the mean directions for
stream-lined landforms are marked with red arrows. The numbers represent orientation in degrees. Mean
directions in degrees are set close to the arrows making it easier to compare the two different types of
values.
9
Figure 6. Interpreted ice-flow direction.
Discussion
There are five areas where striations and stream-lined landforms differ in direction more than
10 degrees or where the stream-lined landforms have an even more significantly different
direction than the striations. The circles A-E in figure 7 display where these areas are located.
If the mean direction between the stream-lined landforms and the mean direction between the
glacial striations differ less than 10 degrees, the measured striations with the round off by 5
degrees may be the cause of the differentiation. More exact measurements of the directions of
the glacial striations need to be made for a better comparison.
10
Figure 7. In area A-E does the directions of striations and stream-lined landforms differ.
In the areas A, C and E in figure 7 the stream-lined landforms have a more westward direction
compared with the glacial striations. The directions between the striations and stream-lined
landforms differ approximately 10-30 degrees. Since the directions of the striations and
stream-lined landforms differ more than 10 degrees the suggestion is that the striations
represent an earlier phase of the ice movement.
In area B the left stream-lined landforms have been formed by either a north or a south
moving ice. The directions of the striations and the other stream-lined landforms in the area
have a more westerly direction. There are not many mapped striations in the area. The
divergence of the directions may be explained in two ways. The stream-lined landforms that
have an N-S orientation are a remnant of a former and older ice event. Or the landforms in NS orientation can be of younger or the same age, and be a part of the Baltic ice stream
mentioned by Möller (1959), and described more thoroughly by Ringberg (2003). Shortly
11
described, the Low Baltic ice stream had a direction to the north. South moving ice changed
direction in the most southern part of Sweden and turned to the north, following the west
coast of Sweden. The Low Baltic ice stream is displayed by Ringberg to have reached its
furthest northern extent to Söderåsen. Söderåsen is situated just north-east of area B,
suggesting that the N/S orientations of the landforms may have been formed by the Low
Baltic ice stream.
In area D the directions of striations and stream-lined landforms differ with more than 40
degrees. The striations represent an older ice event than the stream-lined landforms. The
stream-lined landforms in this area may have formed during an ice-movement from north-east
to south-west, as displayed by the arrows in figure 7. Alternatively, the ice may have moved
in the opposite direction from south-west to north-east. One explanation of the north-east
moving ice and the big difference in directions is the Low Baltic ice stream (Ringberg 2003),
mentioned above. A model by Lagerlund (1987) shows another explanation of a north-east
moving ice. This model shows a marginal dome S-W of Sweden and a main dome in the
Baltic Sea (N-E of the studied area). Lagerlund display that the domes would have caused an
ice-movement from the marginal dome in a north-east direction across the most southern parts
of Sweden. The main statements for this theory are stratigraphic observations that support a
movement in a north-east direction.
Metrics of stream-lined landforms
Method
To see what types of stream-lined geomorphologic landforms being visible in the elevation
map, a simple analysis has been made that include the lengths of the landforms. The lengths
of the drawn lines are determined by using Calculate geometry in the Attribute table function.
In order to visualize the morphology of the stream-lined landforms, surface morphology is
plotted in profiles. Profiles along the length axis of 11 selected stream-lined landforms are
produced as displayed in figure 8. Another profile is drawn from west to east and cross the
area where the 11 landforms are located which is represented by the horizontal line A-B in
figure 8. All of the profiles are created in ArcGIS with 3D analyst tool and the function
Interpolate line. The profiles along the stream-lined landforms are drawn to cover more than
the length of the landforms and starts from a small distance before the visual “beginning” of
the landforms, and the profiles are drawn to end a small distance after the visual “end” of the
landforms.
12
Figure 8. The numbered lines 1-11 are the location of the profiles along the length axis of stream-lined
landforms. The horizontal line A-B represents the location of the profile across the area of the streamlined landforms.
Result
Length
Distribution of length in percent is shown in a frequency curve in figure 9, with more than
1000 measured stream-lined landforms. Mean value of the mapped landforms is 415 m. The
shortest mapped feature is 60 m and the longest is 8380 m. Landforms shorter than 60 m are
hard to see in the scale of the investigation, and are hard to define as a stream-lined landform,
and therefore not mapped.
13
Figure 9. A frequency curve of the lengths that include more than 1200 stream-lined landforms, mapped
in southern Sweden. The x-axis is logarithmic.
The lengths of the stream-lined landforms in this paper are compared with lengths of streamlined landforms from a study by Bennett and Glasser (2009), where the stream-lined
landforms where classified by their length (figure 10). This comparison shows that the
measured stream-lined landforms in my study have the same lengths as drumlins and megaflutes.
Figure 10. A diagram from Bennett (2009), displaying length-frequency of measured stream-lined
landforms classified according to their lengths.
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Profiles
The profile which goes from west to east (A-B) and crosses 11 mapped stream-lined
landforms is shown in figure 11. The green dots represent the locations of the landforms. The
stream-lined landforms are located at the highest areas, but not on all of the highest peaks.
Figure 11. A profile from west to east from the example area. Green dots show where the stream-lined
landforms are located. The horizontal line (A-B) in the lower figure represents the location of the profile.
Profiles along the length axis of the stream-lined landforms are shown in figure 12. The black
dots in figure 12 show the start and end of the stream-lined landforms. The profiles show a
steep end at the proximal part. Line 3 and 4 have a different shape, with a steep distal part,
they are interpreted to have been cut by water erosion. Profile 5 have a shape with several
depressions that also are interpreted to bee caused by water erosion. The 11 stream-lined
landforms in the small investigated area are located in downhill slopes, despite this result, all
stream-lined landforms are not located in downhill slopes.
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Figure 12. Profiles along the length axis of 11 stream-lined landforms. (See figure 5 for location.)
Soil-type
Some of the stream-lined landforms have bare rock on the stoss side, according to the
nationwide soil classification map from SGU. In Sweden, these have been referred to as `leeside moraine´. Due to the ice movements shaping of the landscape, some of the bogs and fens
of today are located in elongated grooves or depressions that have an orientation as the
stream-lined landforms.
16
Figure 13. Soil classification map for an area with stream-lined landforms shown with dark green lines.
The soil map is from Hilldén. SGU.
17
Discussion
Length
Landforms shorter than c. 60 m are not mapped because they are hard to detect on the LiDAR
map in the scale I have worked with. The comparison with the lengths of the observed streamlined landforms with a diagram from Bennett (2009) indicates that most of them are in the
same lengths as drumlins and mega-flutes. To see differences between drumlins and megaflutes the elongation ratios need to be investigated, mega-flutes are more elongated than
drumlins (Benn and Evans, 1998).
Profiles
The locations of the landforms exist on the higher areas, but they are not connected to all of
the highest peaks.
The profiles along the stream-lined landforms in figure 11 tend to have a steep proximal part
and a longer flack distal part. In the profiles it is hard to see a boundary for where the streamlined landforms end, since they tend to have a low angel that flattens out to the same angle as
the land surface. More profiles need to be made to get a better record of the appearance of the
stream-lined landforms.
Soil-type
The nationwide soil classification map from SGU, shows not surprisingly, that most of the
glacial stream-lined landforms exist where the topmost layer is mapped as moraine. Soil maps
show that bogs tend in some areas to have an orientation parallel to the mapped stream-lined
landforms. The internal structure of the stream-lined landforms would be interesting to
investigate to see how the internal structures differ and if there are some regional differences.
Conclusions
The direction of striations and stream-lined landforms correspond quite well. Although in
some areas the two sorts of direction differ to some extent.
The measured stream-lined landforms in my study have the same lengths as drumlins and
mega-flutes. An elongation study must be made to be able to differentiate the drumlins from
mega-flutes.
Some of the stream-lined landforms have bedrock mapped in the proximal part.
Striations have mostly been regarded to as the most important features to estimate ice
movement directions. However, stream-lined landforms should be of the same or even bigger
importance where the numbers of striations are low or non-existing for example in till areas.
18
Further studies
Measurements by using LiDAR- technique are currently ongoing in Sweden, and the
elevation map is not yet fully extended. A more extensive mapping of the stream-lined
landforms could be done to complete the understanding of the ice movement direction in
Sweden. Other features that show ice-movement direction could be compared with each other
to get an even better understanding of the latest ice-movement.
To date the stream-lined landforms one way could be to investigate the former known icemargins to see if the landforms are perpendicular to any of these. The positions of the major
end moraines are a good example of dated ice margins. If the stream-lined landforms are
perpendicular to one of the end moraines, maybe the age of the landforms are approximately
the same as that moraine.
An investigation of the spacing between the stream-lined landforms could also provide more
information about the subglacial conditions of the inland ice.
Acknowledgments
I first want to thank Tore Påsse at SGU for giving me the opportunity to work with this
interesting project and for all the guidance and help. I also want to thank my supervisor Mark
Johnson for all help and inspiration. My mother Marianne Lidhage helped me to improve the
text by reading and commenting it, which I am grateful for.
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laws. Quaternary Science Reviwes, 28, 677-692.
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