Outwash plain
Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 6 "Landforms and their Evolution"
Meaning
An outwash plain is a broad, gently sloping plain beyond the front of a glacier or the edge of an ice sheet. Meltwater streams flow out from the ice and spread gravel, sand, silt and clay over the land in front. Each stream builds a low fan, which is called a glacio-fluvial fan. Many such fans merge side by side into one wide plain. The deposits are roughly sorted and layered because water laid them down. Coarse gravel stays near the ice, and finer silt and clay travel farther.
Example
Skeiðarársandur in southern Iceland is a vast outwash plain in front of the Vatnajökull ice cap. Meltwater rivers spread grey sand and gravel over it all the way to the sea.
Don't confuse with
- Alluvial fan: an alluvial fan is a single cone of coarse load dropped by a mountain stream where it reaches a plain. An outwash plain is a wide sheet of many merging fans built by glacial meltwater.