Abyssal Fans, also known as deep-sea fans, underwater deltas, and submarine fans, are underwater structures that look like deltas

River delta

A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...

 formed at the end of many large rivers, such as the Nile

Nile

The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...

 or Mississippi River

Mississippi River

The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...

s. Abyssal fans are also thought of as an underwater version of alluvial fan

Alluvial fan

An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain. A convergence of neighboring alluvial fans into a single apron of deposits against a slope is called a bajada, or compound alluvial...

s.

Formation

Abyssal (or submarine) fans are formed due to turbidites. Turbidites are essentially gravity-driven underwater avalanches. As sediment is deposited on the continental slope, the steepest part of the ocean, it is prone to sliding down onto the continental rise due to gravity. Once the weight of the sediment accumulating gets to be too much, the pile of sediment will slide down all at once falling down onto the continental rise. After thousands of years of turbidite deposition on the rise, a fan forms towards the top of the continental rise. This fan is similar to an alluvial fan

Alluvial fan

An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain. A convergence of neighboring alluvial fans into a single apron of deposits against a slope is called a bajada, or compound alluvial...

 found on land near mountains and rivers. The abyssal fan has characteristics of a standard turbidite. The Bouma Sequence is used to describe the nature and sediment patterns of a turbidite.

See also

• List of Oceanic Landforms