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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.
Also called alluvial cone.
Origin of alluvial fan
First recorded in 1870-75 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for alluvial fan
Historical Examples
  • In their place an extensive delta and alluvial fan have been formed.

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

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

    Inca Land Hiram Bingham
  • Undoubtedly this alluvial fan had been highly prized in this country of terribly steep hills.

    Inca Land Hiram Bingham
British Dictionary definitions for alluvial fan

alluvial fan

a fan-shaped accumulation of silt, sand, gravel, and boulders deposited by fast-flowing mountain rivers when they reach flatter land
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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alluvial fan in Science
alluvial fan
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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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