In geology, drift is a name for all

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

(

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel ...

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class o ...

, gravel, boulders) transported by a

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...

and deposited directly by or from the ice, or by

glacial A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betwe ...

meltwater. Drift is often subdivided into (unsorted and) unstratified drift (glacial

till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

) that forms moraines and stratified drift (glaciolacustrine and fluvioglacial sediments) that accumulates as stratified and sorted sediments in the form of

outwash plain An outwash plain, also called a sandur (plural: ''sandurs''), sandr or sandar, is a plain formed of glaciofluvial deposits due to meltwater outwash at the terminus of a glacier. As it flows, the glacier grinds the underlying rock surface and c ...

esker An esker, eskar, eschar, or os, sometimes called an ''asar'', ''osar'', or ''serpent kame'', is a long, winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North Ame ...

s, kames,

varve A varve is an annual layer of sediment or sedimentary rock. The word 'varve' derives from the Swedish word ''varv'' whose meanings and connotations include 'revolution', 'in layers', and 'circle'. The term first appeared as ''Hvarfig lera'' (va ...

s, and so forth. The term drift clay is a synonym for

boulder clay Boulder clay is an unsorted agglomeration of clastic sediment that is unstratified and structureless and contains gravel of various sizes, shapes, and compositions distributed at random in a fine-grained matrix. The fine-grained matrix consists o ...

. Both are archaic terms for glacial tills with a fine-grained matrix.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds., 2005. ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. 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 diffrerentiated from underlying bedrock. In this usage, ''drift'' includes a wide variety of deposits, e.g. loess, glacial till, river deposits,

colluvium Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, sheetwash, slow continuous downslope creep, or a variable combinati ...

, and so forth, of Quaternary age. However, this term is most commonly used to specifically describe glacial deposits.Allaby, M., 2013. ''A Dictionary of Geology and Earth Science''. Oxford, United Kingdom, Oxford University Press. 720 pp.

Etymology

In 1839, geologist Roderick MurchisonMurchison, R.I., 1839. ''The Silurian System, Founded on Geological Researches in the Counties of Salop, Hereford, Radnor, Montgomery, Caermarthen, Brecon, Pembroke, Monmouth, Gloucester, Worcester, and Stafford: With Descriptions of the Coalfields and Overlying Formations.'' London, United Kingdom, John Murray, vol. 1, 768 pp. introduced the term ''drift'' to describe unconsolidated surficial sediments previously called ''

diluvium Diluvium is an archaic term applied during the 1800s to widespread surficial deposits of sediments that could not be explained by the historic action of rivers and seas. Diluvium was initially argued to have been deposited by the action of extra ...

''. The term ''drift'' refers to the drift hypothesis proposed by Charles Lyell,Lyell, C., 1833. ''Principles of Geology''. London, United Kingdom, John Murray, vol. 3, 398 pp. as influenced by contemporary polar research, that these sediments had been transported by sea ice and icebergs drifting in marine currents. The drift hypothesis further proposed that these sediments had been released as the ice melted, to fall and accumulate on the sea floor in comparatively recent times, e.g. during the Quaternary Period. This term continued to be used long after the drift hypothesis had been abandoned in favor of the glacial theory.Harland, W.B., Herod, K.N. and Krinsley, D.H., 1966. ''The definition and identification of tills and tillites''. ''Earth-Science Reviews'', 2, pp.225-256.

References

External links

* Glacial deposits {{Glaciology-stub

Etymology

See also

References

External links