alluvial fan

noun

, Physical Geography.

a fan-shaped alluvial deposit formed by a stream where its velocity is abruptly decreased, as at the mouth of a ravine or at the foot of a mountain.

alluvial fan

a fan-shaped accumulation of silt, sand, gravel, and boulders deposited by fast-flowing mountain rivers when they reach flatter land

alluvial fan

/ ə-lo̅o̅′vē-əl /

A fan-shaped mass of sediment, especially silt, sand, gravel, and boulders, deposited by a river when its flow is suddenly slowed. Alluvial fans typically form where a river pours out from a steep valley through mountains onto a flat plain. Unlike deltas, they are not deposited into a body of standing water.

First recorded in 1870–75

Half an hour's walk brought us to Vista Alegre, another little clearing on an alluvial fan in the bend of the river.

Undoubtedly this alluvial fan had been highly prized in this country of terribly steep hills.

In their place an extensive delta and alluvial fan have been formed.

Ancient alluvial fan sequences may also be hydrocarbon reservoirs.

Steep valleys descend from the higher country to join the main valley and at the mouth of every tributary is an alluvial fan.

April 25, 2024firkin

[fur-kin ]

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