Drift (geology)

In geology, drift is a name for all sediment (clay, silt, sand, gravel, boulders) transported by a glacier and deposited directly by or from the ice, or by glacial meltwater. Drift is often subdivided into (unsorted and) unstratified drift (glacial till) that forms moraines and stratified drift (glaciolacustrine and fluvioglacial sediments) that accumulates as stratified and sorted sediments in the form of outwash plains, eskers, kames, varves, and so forth. The term drift clay is a synonym for boulder clay. Both are archaic terms for glacial tills with a fine-grained matrix.^[1]

In the United Kingdom, drift is also applied as a general term for all surficial, unconsolidated, rock debris and sediment that is moved from one place to accumulate in another and mapped separately or otherwise differentiated from underlying bedrock. In this usage, drift includes a wide variety of deposits, e.g. loess, glacial till, river deposits, colluvium, and so forth, of Quaternary age. However, this term is most commonly used to specifically describe glacial deposits.^[1][2]