Transcript for Drift Ice as a Geologic Agent, segment 05 of 11


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Ice keels dragging on the seabed also produce trenches and in the process bulldoze sediment along their path. Grounded flows usually are pushed by surrounding ice and can produce gouges several kilometers long with cross sections up to fifty meters across.

In experiments we dragged concrete blocks of various sizes similar to small ice keels through sand with implanted, painted, and numbered objects in order to model the associated forward sediment transport and attempt quantification. Many years of surveying and precise resurveying have established that ice keels off northern Alaska typically hit a particular spot every twenty-five years. They bulldoze generally from east to west, parallel to depth contours, and can plow the bottom to water depths of sixty meters. The amounts of sediment bulldozed across the shelf are enormous compared to what, for example, is transported in the surf zone.