WATER EROSIONEROSION AND DEPOSITION

Runoff and Erosion Precipitation over the United States averages

about 75 cm per year. About 22.5 cm becomes runoff. Generally, more runoff means more erosion.

Runoff and Erosion Water flowing across the land runs

together to form rills, gullies, and streams.

Erosion by Rivers A waterfall forms where a flat layer of tough rock lies

over a layer of softer rock that erodes easily. When the softer rock erodes, pieces of the harder rock above break off, creating the waterfall’s sharp drop.

Erosion by Rivers Erosion often forms meanders and oxbow

lakes where a river winds across its floodplain.

Deposits by Rivers Deposition creates landforms such as alluvial

fans and deltas.

Alluvial Fan

The Course of a River The slope and size of

a river, as well as the sediment it carries, determine how a river shapes the land.

Groundwater Erosion Karst topography is found in many parts of the

United States where the bedrock is made up of thick layers of limestone.

Groundwater Erosion Chemical weathering of limestone and

groundwater erosion can create a limestone cave.