Surging and supraglacial debris

Model studies suggest that sudden formation of supraglacial debris cover might cause glaciers to advance, by inhibiting ice melt in the lower reaches and altering the driving stresses if the debris deposit is massive enough (basically the weight of the rockfall deposit forces the ice to flow faster). For example, Vacco and others (2010) used a numerical glacier flow-line model with superimposed rock debris to show that a glacier advance caused by deposition of a rock avalanche on the ice will be followed by stagnation of the advanced ice lobe, producing distributed, hummocky deposits quite different from the single moraine ridges typically dated in paleoclimatic reconstructions. This type of rapid advance is different to periodic fast and slow flow that is characteristic of true ‘surge-type’ glaciers.

The cool thing is though that the surface debris cover shows really nice evidence of former surges at the surface of the glacier. For example, look at this photo of the Susitna Glacier in Alaksa:

I found this image on wikiversity, but its credited to Brian John (The image appears on a website entitled, “Stonehenge and the Ice Age” at, though I suspect it might come from the USGS archives originally.

About lindsey

Environmental scientist. I am glaciologist specialising in glacier-climate interactions to better understand the climate system. The point of this is to understand how glaciated envionments might change in the future - how the glaciers will respond and what the impact on associated water resources and hazard potential will be.
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