Glacial geomorphological mapping

This article on glacial geomorphological mapping was written by Dr Benjamin Chandler from Stockholm University.

Why do we map glacial landforms?

Geomorphological mapping is an important method used by glacial geologists to study the behaviour of past glaciers and ice sheets1. By mapping the distribution of glacial landforms and investigating the spatial relationships between different glacial landforms, we can reconstruct the extent and dimensions of former glaciers and ice sheets (see Palaeo-ice sheet reconstruction)2, 3, 4.

The distribution and type of glacial landforms also provide evidence of advance/retreat patterns, flow patterns and thermal regimes of former ice masses5, 6, 7. Palaeoglaciological data extracted from the glacial landform record can then be used to constrain and test numerical models of glaciers and ice sheets8, 9, 10.

Together, these investigations allow us to obtain a better understanding of how glaciers and ice sheets behave over long timescales. Ultimately, this will help scientists to improve predictions of the future response of glaciers and ice sheets to climate change.

Figure 1. Reconstruction of Loch Lomond Readvance (Younger Dryas) outlet glaciers in the Gaick, central Scotland, from glacial geomorphological mapping. Modified from Chandler et al. (2019)3.

We also undertake glacial geomorphological mapping in modern glacial environments, where mapping forms part of studies to devise process-form models and glacial landsystem models. These studies allow us to link glacial processes and landforms directly to particular glaciological and climatic conditions11, 12, 13

We can then use these ‘modern analogues’ to interpret ancient glacial landscapes14, 15, 16, based on the principle of actualism (i.e. present-day glacial processes can explain ancient glacial landforms).

How do we map glacial landforms?

Two main traditions exist in geomorphological mapping. The ‘classical’ approach involves mapping all geomorphological features (e.g. landforms, breaks of slope, slope angles, and drainage), regardless of the different earth surface processes responsible for shaping the landscape17, 18, 19.

The second approach involves thematic geomorphological mapping, which focuses on specific landforms that are relevant to the aims of the study. In glacial geology, we typically follow the second approach and concentrate on mapping glacial landforms, along with associated landforms that can be useful for palaeoglaciological reconstruction (e.g. periglacial landforms)1, 3. This ensures that we do not end up with maps that are cluttered with less relevant information.

To map glacial landforms, we use a variety of methods that cover a range of spatial scales. These methods can be divided into two main categories: (1) field mapping and (2) the interpretation of ‘remotely-sensed’ data (i.e. geospatial data/images captured from an aircraft or satellite).

As best practice, we usually use both field mapping and remote sensing or a combination of different remote-sensing methods1. This allows us to exploit and combine the advantages of the different approaches/datasets to produce an accurate map with robust interpretations of different landforms.

Field mapping

Field mapping involves walking the landscape, with glacial landforms marked onto enlarged topographic maps or printouts of remotely-sensed data (such as aerial photographs). Glacial geologists also use handheld GPS devices to map landforms (using ‘waypoints’) or to help with accurately positioning landforms on field maps.

These days, a smart phone such as an iPhone can provide detailed enough positioning data for geomorphological mapping! The key pieces of equipment a glacial geomorphologist needs in addition to this is a sketch and notebook, and a camera. These are used to sketch and draw landforms and make notes on their characteristics.

The aim of field mapping is to view and assess landforms multiple times from as many perspectives, angles and directions as possible1. This approach gets around potential issues relating to features that may be visible from only one direction or certain angles. Field mapping is valuable for identifying small/low-relief landforms that are not easily seen on remotely-sensed data, as well as those that are hidden by vegetation, clouds or snow cover (for example) on imagery.

Field mapping also allows glacial geologists to identify locations for dating glacial deposits and studying glacial sediments. These can provide us with important information on the timing of glacier fluctuations and depositional processes.

Figure 2. Vectorised version of a field map for part of Glen Odhar in the Monadhliath, Central Scottish Highlands. Modified from Boston (2012)20.

Despite its advantages, field mapping is time consuming, and it can be challenging to accurately map the exact position and shape of landforms in the field.

Because of these factors, glacial geomorphologists often combine field mapping with the interpretation of remotely-sensed data (or ‘remote mapping’)1. This can involve using analogue (hard-copy) aerial photographs (taken from an aeroplane) and/or digital imagery of various types, including images from satellites and drones.

Analogue remote mapping of glacial geomorphology

Mapping from analogue (hard-copy) aerial photographs became a popular approach in glacial geology from the 1960s onwards21, 22, and the approach continues to be used in some glacial geological studies20, 23.  This approach was much more efficient, with previous studies having relied solely on extensive and intensive field mapping.

Aerial photographs are taken from an aeroplane, with the camera usually mounted below the plane and pointing straight down. ‘Oblique’ aerial photographs are taken at an angle (for example, by a person sitting in an aeroplane).

For mapping from aerial photographs, we usually view two overlapping vertical photographs (‘stereopairs’) using an instrument called a stereoscope (with magnification)1. The overlapping photographs provide two different viewing angles of the same area, resulting in a stereoscopic effect (a 3D appearance)24. Mapping from aerial photographs is undertaken by drawing onto an acetate that is overlain on one photograph from a stereopair. This approach can be useful for mapping the location and shape of small features1, 20.

Figure 3. Example of the aerial photograph overlay-mapping process using an example from the mountain Arkle in northwest Scotland. Modified from Lukas and Lukas (2006)25. Aerial photograph: RCAHMS (now Historic Environment Scotland).

Digital remote mapping of glacial geomorphology

The development of GIS software (e.g. commercial: ArcGIS; open source: QGIS) and the widespread availability of digital imagery from satellites and from scanned or digital aerial photographs, has revolutionised geomorphological mapping, and digital remote mapping is now one of the key methods using in glacial geology.

GIS software provides glacial geologists with the tools to visualise, maintain, manipulate and analyse vast amounts of imagery and geomorphological data. Key benefits of digital mapping include the ability to instantaneously alter the viewing scale, easily switch between different imagery/datasets, record georeferenced landform data, extract and record attribute data for individual or groups of landforms, and seamlessly incorporate landform data into larger databases1.

Glacial geomorphologists conduct digital remote mapping directly in GIS software by vectorising glacial landforms (e.g. tracing the crestline or planform of each landform), with individual vector layers created for each glacial landform.

A range of remotely-sensed datasets are used for digital mapping of glacial landforms, including satellite imagery, digital aerial photographs and Digital Elevation Models.

Figure 4. Glacial geomorphological map of the Fjallsjökull foreland, southeast Iceland, produced by digital mapping from a Digital Elevation Model (DEM) and aerial photograph in GIS software. Modified from Chandler et al. (2020)26.

Satellite images

The large footprints of satellite images are ideal for mapping glacial landforms across large areas, such as the landform imprints of former ice streams or entire ice sheets27, 28, 29. Many imaging satellites capture multi-spectral (capturing several parts of the electromagnetic spectrum, not just the visible light part of the spectrum) images, which allows the generation of ‘false-colour composites’ using different combinations of spectral bands.

This can improve landform identification as some landforms are more easily identified using specific band combinations30. Although satellite images offer the benefit of large-area views, there is often a compromise on the ground resolution (pixel size) of non-commercial satellite images. For example, multispectral images from the Landsat satellites have ground resolutions of 15–60 m. This limitation often restricts the use of satellite images to mapping ice-sheet landform imprints1.

Satellite images from the Landsat, ASTER and Sentinel satellites can be accessed for free from services such as USGS EarthExplorer, USGS GloVis and Copernicus Open Access Hub.

Figure 5. Satellite images of glacial lineations. (A) Natural-colour Landsat image of MSGLs near Dubawnt Lake, Canada. Source: Google Earth. (B) False-colour Landsat image of MSGLs Strait of Magellan, Patagonia. Source: Global Land Cover Facility.

Digital aerial photographs

Aerial photography can provide high resolution (ground resolution < 0.5 m per pixel), true-colour (RGB) digital images that are ideal for detailed glacial geomorphological mapping. Overlapping digital aerial photos are usually processed using photogrammetry to produce geometrically “corrected” and georeferenced aerial photograph mosaics (or ‘orthophotos’), which can then be imported into GIS software for on-screen mapping.

Digital aerial photographs are often expensive but there are WMS/WMTS services that can be freely imported into GIS, such as orthophotos for mainland Norway (Norge i Bilder) and Svalbard (Norwegian Polar Institute).

Figure 6. Orthophotos of the Suottasjekna, Vartasjekna and Alep Sarekjekna glacier forelands in Sarek, northern Sweden. Source: Lantmäteriet.

Digital Elevation Models

Digital Elevation Models (DEMs) are raster-based models of topography that record absolute elevation, with each grid cell in a DEM representing the average height for the area it covers. Terrestrial DEMs can be generated by a variety of means, including from surveyed contour data, directly from stereo imagery, or from air- and space-borne radar and LiDAR systems31.

We typically use DEMs to produce ‘hillshaded relief models’ (or ‘hillshades’), which provide visually realistic 3D representations of the land surface for mapping glacial landforms. Examples of freely-available DEMs include ASTER GDEM, the Shuttle Radar Topography Mission (SRTM), and ArcticDEM.

Figure 7. Examples of landforms in relief-shaded DEMs. Red indicates higher elevations and blue lower elevations. (A) Lineations in N Canada shown in 16 m resolution CDED data (Image: Natural Resources Canada). (B) De Geer moraines in SW Finland shown in 2 m resolution LiDAR data (Image: Maanmittauslaitos).

UAV-captured images

The recent emergence of uncrewed aerial vehicles (UAVs) or remotely-piloted aircrafts (RPAs) in glacial geology has enabled images of glacial landforms to be captured at unprecedented ground resolutions (< 0.1 m per pixel)26, 32. The use of UAVs now provides us with a flexible and low-cost approach to capturing up-to-date, high-resolution imagery in glacial environments33.

This has opened up exciting opportunities to undertake repeat surveys at high temporal resolutions (seasonal to annual) in order to monitor landscape at modern glacier margins26.

Figure 8. Hillshades produced from UAV-captured images showing the formation of sub-annual moraines at the margin of Fjallsjökull, southeast Iceland. Modified from Chandler et al. (2020a, b) 13 ,26

What methods do we use in different glacial environments?

We can distinguish two general, overarching ‘work streams’ depending on glacier type:

  • Mapping of ice-sheet geomorphological imprints using a combination of remote mapping methods, with some field checking (where feasible).
  • Mapping of alpine and plateau-style ice mass (cirque glacier, valley glacier, icefield and ice-cap) geomorphological imprints using remote sensing and considerable field mapping/checking.

These two work streams consider the size of the study area, former glacial system and landforms, as well as practical challenges1. The main distinction between the two methodologies is the amount of fieldwork involved (if any). As glacial geologists, we love to go on fieldwork, but it is not time- or cost-effective to map ice-sheet landform imprints in the field. Instead, satellite images and DEMs are commonly used in ice-sheet settings.

By contrast, the smaller areas covered by alpine and plateau-style ice masses allow field mapping.

Irrespective of the glacial environment, a multi-method approach is recommended; multiple remotely-sensed datasets for former ice sheets, and a combination of remote sensing and field mapping for cirque glaciers to ice-caps.

Glacial settingDEMsCoarse satellite imageryLiDAR DEMsHigh-resolution satellite imageryAerial photographsUAV imageryField mapping
Ice sheetsXXX    
Ice sheet sectors/lobesXXX 
Ice-capsXX X
Icefields  XX X
Valley (outlet) glaciers  XXX
Cirque glaciers  XXX
Modern glacier forelands  XXXX
Applicability of the various mapping methods/datasets to different glacial environments1. X = the method/dataset is appropriate and should be used (where the dataset is available). ● = the method is applicable in certain cases, depending on factors such as the resolution of the specific dataset, the size of the study area and landforms, and the accessibility of the study area.

Moving from recording landforms to interpreting landscapes

“When I map, I don’t just go out and record what is there, but engage in a kind of question and answer process with the landscape”

Prof Doug Benn

The previous sections focused on how we record glacial landforms on maps, but geomorphological mapping should not be a purely inductive process (where landforms are mapped and then used to argue towards an interpretation of glacial landscapes).

Glacial geomorphological mapping should instead be conducted within a framework of hypothesis testing and generation. Well-framed hypotheses allow us to anticipate other characteristics of a glacial landscape and to test those predictions by further targeted observations34.

For example, the presence of a certain group of landforms (e.g. moraines trending downslope into a side valley) can be used to formulate hypotheses (e.g. blockage of the side valley by glacier ice and formation of a glacial lake), which in turn can be used to predict the presence of other glacial landforms/sediments in a particular location (e.g. lacustrine sediments or shoreline terraces in the side valley). Further investigations would allow testing and falsification of alternative working hypotheses35, 36. Iterations of this process during mapping enable us to obtain an increasingly detailed and robust understanding of the glacier system.

Further reading

This page is a summary of a detailed review that was published in Earth-Science Reviews:

Chandler, B.M.P., et al. 2018. Glacial geomorphological mapping: A review of approaches and frameworks for best practice. Earth-Science Reviews 185, 806–846.

The accepted version of the paper is freely available on ResearchGate or from the author (see below).

References

[1] Chandler, B.M.P., Lovell, H., Boston, C.M., Lukas, S., Barr, I.D., Benediktsson, Í.Ö., Benn, D.I., Clark, C.D., Darvill, C.M., Evans, D.J.A., Ewertowski, M.W., Loibl, D., Margold, M., Otto, J.-C., Roberts, D.H., Stokes, C.R., Storrar, R.D., Stroeven, A.P., 2018. Glacial geomorphological mapping: A review of approaches and frameworks for best practice. Earth-Science Reviews 185, 806–846.

 

[2] Clark, C.D., Hughes, A.L.C., Greenwood, S.L., Jordan, C., Sejrup, H.P., 2012. Pattern and timing of retreat of the last British-Irish Ice Sheet. Quaternary Science Reviews 44, 112–146.

 

[3] Chandler, B.M.P., Boston, C.M., Lukas, S., 2019. A spatially-restricted Younger Dryas plateau icefield in the Gaick, Scotland: Reconstruction and palaeoclimatic implications. Quaternary Science Reviews 211, 107–135.

 

[4] Davies, B.J., Darvill, C.M., Lovell, H., Bendle, J.M., Dowdeswell, J.A., Fabel, D., García, J.-L., Geiger, A., Glasser, N.F.,
Gheorghiu, D.M., Harrison, S., Hein, A.S., Kaplan, M.R., Martin, J.R.V.,
Mendelova, M., Palmer, A., Pelto, M., Rodés, Á., Sagredo, E.A., Smedley, R.K., Smellie, J.L., Thorndycraft, V.R., 2020. The evolution of the Patagonian Ice Sheet from 35 ka to the present day (PATICE). Earth-Science Reviews 204, 103152.

 

[5] Lukas, S., Benn, D.I., 2006. Retreat dynamics of Younger Dryas glaciers in the far NW Scottish Highlands Reconstructed from moraine sequences. Scottish Geographical Journal 122, 308–325.

 

[6] Hughes, A.L.C., Clark, C.D., Jordan, C.J., 2014. Flow-pattern evolution of the last British Ice Sheet. Quaternary Science Reviews 89, 148–168.

 

[7] Darvill, C.M., Stokes, C.R., Bentley, M.J., Evans, D.J.A., Lovell, H., 2017. Dynamics of former ice lobes of the southernmost Patagonian Ice Sheet based on a glacial landsystems approach. Journal of Quaternary Science 32, 857–876.

 

[8] Golledge, N.R., Hubbard, A., Sugden, D.E., 2008. High-resolution numerical simulation of Younger Dryas glaciation in Scotland. Quaternary Science Reviews 27, 888–904.

 

[9] Seguinot, J., Rogozhina, I., Stroeven, A.P., Margold, M., Kleman, J., 2016. Numerical simulations of the Cordilleran ice sheet through the last glacial cycle. The Cryosphere 10, 639–664.

 

[10] Ely, J.C., Clark, C.D., Hindmarsh, R.C.A., Hughes, A.L.C., Greenwood, S.L., Bradley, S.L., Gasson, E., Gregoire, L., Gandy, N., Stokes, C.R., Small, D., 2019. Recent progress on combining geomorphological and geochronological data with ice sheet modelling, demonstrated using the last British–Irish Ice Sheet. Journal of Quaternary Science, in press.

 

[11] Benediktsson, Í.Ö., Jónsson, S.A., Schomacker, A., Johnson, M.D., Ingólfsson, Ó., Zoet, L., Iverson, N.R., Stötter, J., 2016. Progressive formation of modern drumlins at Múlajökull, Iceland: stratigraphical and morphological evidence. Boreas 45, 567–583.

 

[12] Ewertowski, M.W., Evans, D.J.A., Roberts, D.H., Tomczyk, A.M., Ewertowski, W., Pleksot, K., 2019. Quantification of historical landscape change on the foreland of a receding polythermal glacier, Hørbyebreen, Svalbard. Geomorphology 325, 40–54.

 

[13] Chandler, B.M.P., Evans, D.J.A., Chandler, S.J.P., Ewertowski, M.W., Lovell, H., Roberts, D.H., Schaefer, M., Tomczyk, A.M., 2020. The glacial landsystem of Fjallsjökull, Iceland: Spatial and temporal evolution of process-form regimes at an active temperate glacier. Geomorphology 361, 107192.

 

[14] Evans, D.J.A., Lemmen, D.S., Rea, B.R., 1999. Glacial landsystems of the southwest Laurentide Ice Sheet: modern Icelandic analogues. Journal of Quaternary Science 14, 673–691.

 

[15] Darvill, C.M., Stokes, C.R., Bentley, M.J., Evans, D.J.A., Lovell, H., 2017. Dynamics of former ice lobes of the southernmost Patagonian Ice Sheet based on a glacial landsystems approach. Journal of Quaternary Science 32, 857–876.

 

[16] Sutherland, J.L., Carrivick, J.L., Evans, D.J.A., Shulmeister, J., Quincey, D.J., 2019. The Tekapo Glacier, New Zealand, during the Last Glacial Maximum: An active temperate glacier influenced by intermittent surge activity. Geomorphology 343, 183–210.

 

[17] Demek, J., 1972. Manual of detailed geomorphological mapping. IUG, Prague 344 pp.

 

[18] Gustavsson, M., Seijmonsbergen, A.C., Kolstrup, E., 2008. Structure and contents of a new geomorphological GIS database linked to a geomorphological map – With an
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[19] Loibl, D., Lehmkuhl, F., 2013. High-resolution geomorphological map of a low mountain range near Aachen, Germany. Journal of Maps 9(2), 245–253.

 

[20] Boston, C.M., 2012. A glacial geomorphological map of the Monadhliath Mountains, Central Scottish Highlands. Journal of Maps 8 (4), 437–444.

 

[21] Prest, V.K., Grant, D.R., Rampton, V.N., 1968. Glacial map of Canada. Geological Survey of Canada, Map 1253A.

 

[22] Evans, D.J.A., 2009. Glacial Geomorphology at Glasgow. Scottish Geographical Journal 125, 285–320.

 

[23] Evans, D.J.A., Orton, C., 2015. Heinabergsjökull and Skalafellsjökull, Iceland: Active Temperate Piedmont Lobe and Outwash Head Glacial Landsystem. Journal of Maps 11 (3), 415–431.

 

[24] Lillesand, T.M., Kiefer, R.W., Chipman, J.W., 2015. Remote Sensing and Image Interpretation (7th Edition). John Wiley & Sons, Hoboken, USA 768 pp.

 

[25] Lukas, S., Lukas, T., 2006. A glacial geological and geomorphological map of the far NW Highlands, Scotland. Parts 1 and 2. Journal of Maps 2, 43–56, 56–58.

 

[26] Chandler, B.M.P., Chandler, S.J.P., Evans, D.J.A., Ewertowski, M.W., Lovell, H., Roberts, D.H., Schaefer, M., Tomczyk, A.M., 2020. Sub-annual moraine formation at an active temperate Icelandic glacier. Earth Surface Processes and Landforms 45, 1622–1643.

 

[27] Stokes, C.R., Clark, C.D., 2003. The Dubawnt Lake palaeo-ice stream: evidence for dynamic ice sheet behaviour on the Canadian Shield and insights regarding the controls on ice-stream location and vigour. Boreas 32, 263–279.

 

[28] Kleman, J., Jansson, K., De Angelis, H., Stroeven, A.P., Hättestrand, C., Alm, G., Glasser, N., 2010. North American Ice Sheet build-up during the last glacial cycle, 115–21kyr. Quaternary Science Reviews 29, 2036–2051.

 

[29] Storrar, R.D., Stokes, C.R., Evans, D.J.A., 2013. A map of large Canadian eskers from Landsat satellite imagery. Journal of Maps 9, 456–473.

 

[30] Jansson, K.N., Glasser, N.F., 2005. Using Landsat 7 ETM+ imagery and Digital Terrain Models for mapping glacial lineaments on former ice sheet beds. International Journal of Remote Sensing 26(18), 3931–3941.

 

[31] Smith, M.J., Clark, C.D., 2005. Methods and visualisation of digital elevation models for landform mapping. Earth Surface Processes and Landforms 30, 885–900.

 

[32] Ely, J.C., Graham, C., Barr, I.D., Rea, B.R., Spagnolo, M., Evans, J., 2017. Using UAV acquired photography and structure from motion techniques for studying glacier landforms: application to the glacial flutes at Isfallsglaciären. Earth Surface Processes and Landforms 42(6), 877–888.

 

[33] Ewertowski, M.W., Tomczyk, A.M., Evans, D.J.A., Roberts, D.H., Ewertowski, W., 2019. Operational Framework for Rapid, Very-high Resolution Mapping of Glacial Geomorphology Using Low-cost Unmanned Aerial Vehicles and Structure-from-Motion Approach. Remote Sensing 11, 65.

 

[34] Benn, D.I., 2006. Interpreting glacial sediments. In: Knight, P. (Ed.), Glacier Science and Environmental Change. Blackwell, Oxford, pp. 434–439.

 

[35] Chamberlin, T.C., 1897/1965. The method of multiple working hypotheses. Science 148, 745–759.

 

[36] Popper, K.R., 1972. Objective Knowledge. Oxford University Press, Oxford.

 

About the author

Dr Benjamin Chandler is a researcher at Stockholm University. His research interests are focused on understanding the dynamics of mountain glaciers and ice-caps and their response to climate change. This involves a combination of glacial geomorphological mapping, sedimentology, near-surface geophysics, and/or remote sensing.

Departmental webpage | Personal website | ResearchGate | Google Scholar

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