Introduction to glacial landsystems

What are glacial landsystems | The landsystems approach | Studying landform–sediment assemblages | Why are glacial landsystems useful? | Summary | Key terms | References

What are glacial landsystems?

Research in glacial geology has increasingly concentrated on glacial landsystems1,2. In broad terms, the landsystems concept attempts to understand how a landscape was created through investigation of the complete collection of landforms and sediments within it.

Formally, a landsystem can be defined as1:

An area with a common set of features that is different to that of neighbouring areas. This includes the surface topography (of which landforms are a part), but also its underlying sediments and soils, and overlying vegetation.

There are two key principals to the landsystem approach:

The first is that landforms (such as an esker, moraine, or roche moutonnée) and sediments are considered not in isolation, but in combination as landform–sediment assemblages that make up a landscape (see “Key terms” at bottom of page).

The second is that, in landsystems research, the emphasis is on linking landform–sediment assemblages to the processes that create them – to produce process–form models – which, when applied to a particular landscape, can even be linked to local environmental (e.g. climate) and geological (e.g. topography) controls.

The glacial tongue and foreland of Skaftafellsjökull glacier in Iceland, with assemblages of closely-spaced sawtooth push moraines. Iceland has been an important testing ground for the study of process–form models at active glacier margins (see Evans, 2003; ref. 1) Photo: Chensiyuan

The landsystems approach

For the landsystems approach to be effective, glacial geologists must carefully study the glacial landform–sediment assemblages of two settings:

One – they investigate the landforms and sediments being actively created in currently glaciated areas (such as Iceland, the European Alps, or the Southern Alps of New Zealand) to establish clear links with the glaciological processes that produce them, and;

The partially debris-covered terminus of the Fox Glacier, South Island, New Zealand, in 2013. Here, a glacial geologist could study the process–form relationships of a temperate valley glacier with a high supraglacial debris load. Photo: M. Basler

Two – they study the landforms and sediments of areas where glaciers are no longer present (such as the British Isles) to reconstruct past glacial systems and the processes that operated within them.

The cirque floor of Cwm Idwal, North Wales, with a chain of moraine ridges flanking Llyn (lake) Idwal and a staircase sequence of lateral moraines descending the opposite valley side (right of image). This is a good example of landform–sediment assemblages produced by a small cirque glacier during the Loch Lomond Stadial in upland Britain. Photo: J. Bendle.

From this, you should see that the accuracy of the landsystem approach – and the reconstruction of former glacier systems – relies on a clear understanding of the processes that create specific landform–sediment assemblages at active glaciers – i.e. on process–form relationships.

Studying landform–sediment assemblages

In practice, studying process–form relationships at active glaciers, and the application of the landsystem approach to a formerly glaciated landscape, involve broadly the same method: a detailed physical inspection of the landscape to identify landform–sediment assemblages and patterns in their spatial distribution.

This is typically achieved by mapping the type, size, and shape of landforms from aerial and satellite imagery, or through fieldwork (this can even be achieved using Google Earth imagery, making it an interesting and accessible topic for A-level and undergraduate research projects).

Google Earth image of the Skálafellsjökull glacier margin and immediate foreland (Iceland). Glacial geologists use satellite images such as this to map the type and distribution of landform–sediment assemblages.

In addition, the sedimentological characteristics of landform-assemblages – for example, the size, shape, and roundness of particles in a moraine – are recorded in the field or analysed in a laboratory. This extra information tells us much about how a feature was formed, such as whether the sediment was laid down directly by ice or by glacial meltwater2,3.

Exposure in the ‘Little Ice Age’ moraine of the Exploradores Glacier, Patagonia (South America). Glacial geologists carefully record the constituents (e.g. the size, roundness and shape of particles) of landforms such as moraines to better understand how they were created. Photo: J. Bendle

Why are glacial landsystems useful?

One of the main advantages of the landsystems approach is the ability to reconstruct – not just the size and shape of former glaciers – but the distinct characteristics of these glaciers and the processes that once operated there, more accurately and in much greater detail than is possible by studying individual landforms in isolation1.

One example would be the ability to determine the thermal regime of a former glacier based on the suite of landform-sediment assemblages it left behind. Active temperate (warm-based) glaciers, for example, are often associated with low-amplitude push, dump and squeeze moraines, flutes, drumlins, and glaciofluvial features, such as eskers and outwash plains4,5. These assemblages develop under wet-based conditions that encourage basal sliding and subglacial deformation. Cold-based glaciers, by contrast, which are frozen to their beds, produce different landform–sediment assemblages typified by ice-contact fans, thrust-block moraines, and periglacial screes, with no subglacial features like flutes and drumlins6,7.

Google Earth image of the Svínafellsjökull glacier (Iceland) showing the landform–sediment assemblages typical of an active temperate glacier margin, such as flutes and debris stripes, sawtooth push moraines, and outwash deposits (see ref. 8)

Another advantage of the landsystem approach occurs where distinctive landform-sediment assemblages overprint or overlap one another, as they contain evidence of temporal changes in glacier processes or characteristics. One example relates to assemblages of cross-cutting drumlins (and/or other subglacially moulded landforms) or bedrock striations, which indicate changes in the direction of ice flow over time.

Summary

The landsystems approach is a holistic method of studying glacier and landscape history that (i) makes inferences using the full suite of landform–sediment assemblages that constitute a landscape, and (ii) is supported by process–form models established at active glaciers.

Other pages in this section of the website give examples of the main glacial landsystems to be identified in both actively and formerly glaciated areas.

Key terms

Landform-sediment assemblage: a distinctive group of landforms and sediments that together reflect a common process or age. A glaciated landscape is typically made up of lots of distinctive landform–sediment assemblages related to different (e.g. subglacial, supraglacial, ice-marginal) processes.

Process–form model: a theoretical model (based on detailed observation) that links physical processes to the landforms and sediments they create. In glaciated systems, processes of glacier erosion, ice and debris transfer, and deposition create landform–sediment assemblages.

References

[1] Evans, D.J.A., 2003. Glacial landsystems. Hodder–Arnold.

[2] Benn, D.I., and Evans, D.J.A., 2014. Glaciers and glaciation. Routledge.

[3] Evans, D.J.A., and Benn, D.I., 2004. The practical guide to the study of glacial sediments. Hodder–Arnold

[4] Evans, D.J.A., and Twigg, D.R., 2002. The active temperate glacial landsystem: a model based on Breiðamerkurjökull and Fjallsjökull, Iceland. Quaternary Science Reviews21 (20-22), 2143-2177.

[5] Evans, D.J.A., 2003. Ice-marginal terrestrial landsystems: active temperate glacier margins (ed.) in Evans, D.J.A., Glacial Landsystems. Hodder–Arnold, pp. 89-110.

[6] Fitzsimons, S.J. 2003. Ice-marginal terrestrial landsystems: polar continental glacier margins (ed.) in Evans, D.J.A., Glacial Landsystems. Hodder–Arnold, pp. 89-110.

[7] Hambrey, M.J., and Fitzsimons, S.J., 2010. Development of sediment–landform associations at cold glacier margins, Dry Valleys, Antarctica. Sedimentology57 (3), 857-882.

[8] Evans, D.J.A., Ewertowski, M.W., and Orton, C., 2019. The glacial landsystem of Hoffellsjökull, SE Iceland: contrasting geomorphological signatures of active temperate glacier recession driven by ice lobe and bed morphology. Geografiska Annaler: Series A, Physical Geography101 (3), 249-276.

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