alluvial fan

American  

noun

Physical Geography.

1. 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.

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alluvial fan British  

noun

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

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alluvial fan Scientific  

/ ə-lo̅o̅′vē-əl /

1. 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.

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Etymology

Origin of alluvial fan

First recorded in 1870–75

Example Sentences

See Examples For:

alluvial fan

It’s a desolate alluvial fan on the southern flanks of the Cady Mountains, where sparkling calcite crystals and pieces of quartz, jasper and agate are continually carried down the slopes by thunderstorms and flash floods.

From Los Angeles Times ● Jul. 16, 2023

A man stands on an alluvial fan below Tumacacori mountain, a few dozen miles north of here.

From The Guardian ● Mar. 1, 2017

The most distinctive alluvial sedimentary deposit is the alluvial fan, a large cone of sediment formed by streams flowing out of dry mountain valleys into a wider and more open dry area.

From Textbooks ● Jan. 1, 2017

The trip I joined was part of a 67-day, 1,058-mile “first,” paddling the Cuito tributary of the Okavango river, which rises in the Angolan Highlands before tipping through Namibia into the alluvial fan in Botswana.

From The Wall Street Journal ● Jul. 30, 2015

Page 283 Half an hour's walk brought us to Vista Alegre, another little clearing on an alluvial fan in the bend of the river.

From Inca Land Explorations in the Highlands of Peru by Bingham, Hiram