Are there debris-covered glaciers in Antarctica? And if so, where are they?

Asked by Pierre

Debris-covered glaciers, those glaciers with layers of rock and debris on their surface, occur world-wide. They form part of a continuum with other icy, rocky features, such as rock glaciers. Debris-covered glaciers and rock glaciers both flow, resulting in their lobate forms. Rock glaciers are one end-member, with higher amounts of debris held together largely by interstitial ice, and clean ice is at the other end of the spectrum, with very little debris on the ice surface. The proportion of rock and ice within and on top of the ice is highly variable.

Debris-covered glaciers and rock glaciers

Debris-covered glaciers and rock glaciers form when a high amount of debris falls on the ice surface. Debris-covered glaciers are not known from the interior of the Antarctic Ice Sheet, because the large ice sheet overwhelms local topography, meaning that a steady supply of rock is not available. To find them, we must look to the fringes of the Antarctic Ice Sheet.

Rocks glaciers on the Antarctic Peninsula

Rock glacier on James Ross Island

Rock glaciers are common on the Antarctic Peninsula, particularly on James Ross Island1, as shown in the photograph above. They form here at the base of scree slopes, and extensive periglacial activity ensures a steady supply of rocks. I have also observed them on Alexander Island, at Fossil Bluff.

Debris-covered glaciers in the Dry Valleys

The other place where debris-covered glaciers occur is in the Dry Valleys of East Antarctica2. Compared with the Antarctic Peninsula, this area receives very little precipitation and the glaciers flow very slowly. Some of the glacier ice is millions of years old. Because of the limited precipitation, rocks falling steadily onto the surface of the glaciers builds up, resulting in debris-covered glaciers.

 

1.            Davies, B.J., Glasser, N.F., Carrivick, J.L., Hambrey, M.J., Smellie, J.L., & Nývlt, D. Landscape evolution and ice-sheet behaviour in a semi-arid polar environment: James Ross Island, NE Antarctic Peninsula. in Antarctic Palaeoenvironments and Earth-Surface Processes, M.J. Hambrey, P.F. Barker, P.J. Barrett, V.C. Bowman, B.J. Davies, J.L. Smellie, and M. Tranter, Editors. 2013, Geological Society, London, Special Publications, volume 381: London. 353-395.

2.            Shean, D.E. &Marchant, D.R. Seismic and GPR surveys of Mullins Glacier, McMurdo Dry Valleys, Antarctica: ice thickness, internal structure and implications for surface ridge formation. Journal of Glaciology. 56, 48-64 (2010).

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