What does outwash mean?
Outwash is the sand, gravel, and finer sediment deposited by meltwater leaving a glacier. As a glacier retreats, streams carry debris beyond its edge and spread it across the landscape, creating level outwash plains, terraces, and aprons. The term is most often used in geology, geomorphology, and related field sciences, though it also appears in descriptions of soils and landforms in formerly glaciated regions, especially in North America and northern Europe. Outwash is valuable to geologists because its grains and layering record how glacial meltwater behaved and how the landscape changed during deglaciation. In ordinary speech, the word is uncommon and technical. Although it can sometimes be confused with alluvium, alluvium refers broadly to material deposited by flowing water, whereas outwash is specifically associated with glacial meltwater.
nounMaterial, chiefly sand, gravel, and finer sediment, deposited by meltwater flowing from the front of a glacier. The term may also refer to the deposit or landform formed by such material.
- Sediment deposited by meltwater issuing from a glacier, including the associated deposit or landform.
"The farmers built a road across the sandy outwash beyond the terminal moraine."
"Meltwater spread sand and gravel across the valley, creating a broad outwash plain."
"The soil samples contained gravel typical of glacial outwash."
Outwash is usually used as a mass noun, but the plural outwashes is used when referring to distinct deposits or outwash areas.
"Several outwashes are visible beyond the ridge."
A glacier's meltwater does more than carry rock dust away—it lays down the flat plains that later hold farms and towns.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does outwash come from?
Outwash is an English compound formed from the elements out and wash, describing material carried outward from a glacier by meltwater. The compound became established in English geological vocabulary for the sediment and landforms associated with glacial drainage. Its second element, wash, is a native Germanic word cognate with German waschen and Dutch wassen, all meaning “to wash.”
How outwash is actually used
This is primarily a technical term in geology, geomorphology, and soil science rather than everyday vocabulary. It is especially common in descriptions of formerly glaciated landscapes in North America and northern Europe.
Easily confused with outwash
A washout is a place where water or erosion has removed material, such as a damaged road, whereas outwash is sediment deposited by glacial meltwater.