flash flooding in the desert showing muddy runoff flowing over bedrock
In arid areas where vegetation is sparse, heavy rainfall can cause flash flooding. Runoff after a storm in the lower Park Avenue area of Arches National Park, Utah.

NPS photo.

When a rock particle (loosened by one of the two weathering processes) is moved by some flowing agent such as air, water or ice the process is called erosion.

Glacier Ice

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    Flowing Water

    Rivers and Streams


    Sand, gravel, and silt deposited by rivers and streams in a valley bottom.

    Alluvial Fan

    A fan-shaped pile of sediment that forms where a rapidly flowing mountain stream enters a relatively flat valley. As water slows down, it deposits sediment (alluvium) that gradually builds a fan.

    Coastal and Shorline Processes


    Aeolian is the technical term for wind-driven erosion and transportation, wind-blown sediment (such as sand and silt), and wind generated deposits (such as sand dunes).

    Last updated: September 9, 2019