Outwash deposit
Also called: Glacio-fluvial deposit · Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 6 "Landforms and their Evolution"
Meaning
An outwash deposit is debris that meltwater streams carry away from a glacier and lay down. The water flows out from the bottom, sides or snout of the glacier. Because running water moves these materials, it sorts them roughly by size and lays them in layers. It also rubs the fragments, so they are somewhat rounded. That is why outwash is also called a glacio-fluvial deposit: it is laid down by glacier meltwater ("glacio") acting like a river ("fluvial"). Eskers and outwash plains are made of it.
Example
The Canterbury Plains on New Zealand's South Island are largely built of outwash gravels. Meltwater rivers carried them down from the glaciers of the Southern Alps.
Don't confuse with
- Glacial till: melting ice drops till directly, so it is unsorted and angular. Outwash is roughly sorted, layered and somewhat rounded.