till

The surface of the ground in this area adjacent to Sherman glacier is covered with a coarse glacial till. Chugach Mountains, Chugach National Forest, Alaska. Credit: USGS

Also known as boulder clay, the unsorted material left behind on the land after the retreat of a glacier. Till is a heterogeneous mixture of different sized material deposited by moving ice (lodgement till) or by the melting in-place of stagnant ice (ablation till). After deposition, some tills are reworked by water.

See also drift, drumlin, moraine.

Related category

• GEOLOGY AND PLANETARY SCIENCE

Source: USGS

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