Alluvial Fan

Alluvial Fan Landforms

Alluvial fan landforms have 2 main characteristics:

  1. Fan or cone shaped
  2. Build up of sedimentary material such as gravel and silt

Examples of Alluvial Fan Landforms:

Death Valley National Park, California, USA

Near the mountains south of the Taklamakan Desert in Xinjiang, China lies an alluvial fan 25 miles long and nearly as wide. The best example of an alluvial fan is the one in Nepal created by the streaming Koshi River. It has an area of almost 15000 square kilometers.

 What is an Alluvial Fan Landform?

An alluvial fan is a fan-shaped or triangular pattern of sand, gravel or other sediment that is spread by water over an area of the ground, hillside or mountain.

 How are alluvial fans formed?

An alluvial fan is formed by running water like rivers and streams that carries sand, gravel or other sediment over the ground, hillside or mountain. It begins from a single point and is spread by the movement of water that flows over the area. If an alluvial fan happens on a steep mountainside, it can be very narrow. Over flat areas of land, the fan shape can be very wide.

Where can an Alluvial Fan be Found?

An alluvial fan may be found in the desert where flooding has occurred. Occasional heavy rainfall causes water to rush over some areas of the desert, creating patterns on the ground. Alluvial fans also occur on hillsides and mountainsides where water escapes from a single point as water from rainfall flows downward. They sometimes occur when rivers rise during periods of heavy rainfall. Water can escape the river at one point, flowing outward over the land to create a fan shaped pattern. They can even be found underwater, created by currents that move sediment over the sea floor.

How Large is an Alluvial Fan?

An alluvial fan can be as small as a few inches, or it can be many miles wide. A portion of the Koshi river in Nepal has created an alluvial fan that covers almost 6000 square miles of land.

 Famous Alluvial Fans:

  • Death Valley National Park, California, USA
  • Planet Mars
  • Taklimakan Dessert, Xin Jiang, China
  • Zagros Mountains, Iran

Parts of an Alluvial fan

The apex is the narrower part of the alluvial fan and the apron is the wide triangle. The apron of an alluvial fan can have length of just a few centimeters dispersing out from the drops of water out of a drainpipe. This means that alluvial fans can really be small. On the other hand, there are alluvial fans that can show great lengths and widths.

Can You Live on an Alluvial Fan?

Areas where alluvial fans occur can be flooded again and again when there is heavy rainfall. Building a home on an alluvial fan is not a good idea.

Alluvial fan definition:

A fan shaped or triangular pattern of sand, gravel or other sediment that is spread by water over an area of the ground, hillside or mountain

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