Introduction

Glacial Landforms

There is a huge variety of glacial landforms recognised in the geological record. However, they are difficult to see in Antarctica, because they are usually buried beneath ice. On a few small islands around the Antarctic Peninsula, however, you can see evidence of past glaciations through glacier sediments and landforms. On the next few pages, you can learn more about different kinds of glacial landforms found around Antarctica. See:

Types of glacial landform

The types of landforms that are generated are particular to glacier flow, basal processes, the substrate (soft and deformable? Hard crystalline bedrock?), the basal driving stress and thermal regime, and the ice temperature. There are diagnostic landforms associated with wet-based sheet flow, ice streams, and surging ice. Surging glaciers are a particular phenomenon where the ice flows periodically fast and then more slowly, and are uncommon in Antarctica. On the other hand, the continental shelf around the Antarctic Peninsula is littered with landforms diagnostic of ice streams. The onshore glaciers around the Antarctic Peninsula, instead, are polythermal or cold-based.

Some different types of glacial landforms under different ice flow regimes

Streaming ice Surging ice Sheet flow Cold-based ice
Mega scale glacial lineations (MSGLs) Looped medial moraines Marginal / subglacial / glaciofluvial domains May be very little modification of previous landforms
Progressive elongation of landforms down-ice Thrusted end moraines Push, dump, squeeze moraines Small glaciotectonic structures
Trough mouth fans Concertina eskers Subglacial till, flutes, drumlins, overridden moraines Some deposits with a coarse, sandy to boulder-gravel texture.
Till, glaciotectonised sediments Till, glaciotectonite, complex till stratigraphies Roche moutonnees, striated and polished bedrock Little evidence of fluvial reworking, but aeolian reworking may be common.
Drumlins, meltwater channels, terminal moraines, grounding lines Crevasse-squeeze ridges; flutings Till, glaciotectonite
“Sticky spots” (bedrock bumps/cold-based ice/dry bed) Hummocky moraine Sandur, eskers, kame terraces,  proglacial lakes, braided channels, pitted outwash

The contrast between landforms being made by different processes is clear around the Antarctic Peninsula. Small islands and ice-free areas, such as James Ross Island, are characterised by small moraines made by polythermal glaciers. However, on the continental shelf, there are large landforms generated by ice streams at the Last Glacial Maximum (LGM). The next section contrasts these different environments and their landforms.

James Ross Island

Geological map of James Ross Island, NE Antarctic Peninsula

Some of our examples of glacial landforms come from James Ross Island, which is located on the northeast tip of the Antarctic Peninsula, at about 64°S (see map below)[1]. The area was glaciated during the Last Glacial Maximum, with cosmogenic nuclide exposure ages indicating recession of the main glacier ice around 11,000 to 9500 years ago[2] (see ice sheet evolution). The landscape is now characterised by permafrost (see Periglaciation)[3, 4], with small cold and polythermal glaciers, and periglacial landforms, such as rock glaciers[5], protalus ramparts, patterned ground, snow patches and small ephemeral streams.

The most obvious glacier landforms on James Ross Island are ice-cored moraines around small glaciers on Ulu Peninsula. These glaciers are surrounded by sharp-crested moraines with a core of glacier ice. The glacier ice is stratified with blue and white, bubble-rich ice and debris-rich bands, suggesting that it is basal glacier ice. The crests of the moraines range from sharp-crested to chaotic, with the ice wasting and melting in situ. The buried glacier ice means that water cannot drain away, and many small frozen and unfrozen lakes and ponds are impounded on the moraines.

You can see many more examples of glacial landforms on the Glaciers Online photoglossary.

Go to top or jump to Dating Glacial Sediments.

References


1.            British Antarctic Survey, Antarctic Sound and James Ross Island, Northern Antarctic Peninsula, in Series BAS (UKAHT) Sheets 3A and 3B, 1:250000. 2010, United Kingdom Antarctic Heritage Trust: Cambridge.

2.            Johnson, J.S., Bentley, M.J., Roberts, S.J., Binney, S.A., and Freeman, S.P.H.T., 2011. Holocene deglacial history of the north east Antarctic Peninsula – a review and new chronological constraints. Quaternary Science Reviews, 2011. 30(27-28), 3791-3802

3.            Fukuda, M., Strelin, J.A., Shimokawa, K., Takahashi, N., Sone, T., and Trombott, D., 1992. Permafrost occurrence of Seymour Island and James Ross Island, Antarctic Peninsula region, in Recent progress in Antarctic Earth Sciences, N. Yoshida, K. Kaminuma, and K. Shiraishi, Editors. Terra Scientific Publishing Company (TERRAPUB): Tokyo. p. 745-750.

4.            Lundqvist, J., Lillieskold, M., and Ostmark, K., 1995. Glacial and periglacial deposits of the Tumbledown Cliffs area, James Ross Island, West Antarctica. Geomorphology, 1995. 11: p. 205-214.

5.            Fukui, K., Sone, T., Strelin, J.A., Torielli, C.A., Mori, J., and Fujii, Y., 2008. Dynamics and GPR stratigraphy of a polar rock glacier on James Ross Island, Antarctic Peninsula. Journal of Glaciology, 2008. 54: p. 445-451.

6.            Davies, B.J., Hambrey, M.J., Smellie, J.L., Carrivick, J.L., and Glasser, N.F., 2012. Antarctic Peninsula Ice Sheet evolution during the Cenozoic Era. Quaternary Science Reviews, 2012. 31(0): p. 30-66.

7.            Graham, A.G.C., Larter, R.D., Gohl, K., Hillenbrand, C.-D., Smith, J.A., and Kuhn, G., 2009. Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control. Quaternary Science Reviews, 2009. 28(25-26): p. 2774-2793.

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