Alluvial Fan

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alluvial fan

[ə′lüv·ē·əl ′fan]
A fan-shaped deposit formed by a stream either where it issues from a narrow moutain valley onto a plain or broad valley, or where a tributary stream joins a main stream.

Alluvial Fan


a type of relief in the form of a slightly convex fan, formed through the accumulation of loose detrital material in the estuarine part of temporary streams and small rivers where they emerge from mountains onto piedmont plains or from gorges onto broader valleys. It forms as the result of the deposition of material suspended in water when the speed of the current of water decreases owing to a change in gradient. Populated areas are frequently situated on alluvial fans.

References in periodicals archive ?
The age of alluvial fan deposition at a site in the Southern Uplands of Scotland, Earth Surfaces Processes and Landforms 19: 333-48.
In Holocene time, regional uplift, or movement along the Cerro Bola fault, possibly in addition to climatic change, caused dissection of the older pediment and alluvial fans, and creation of new, younger alluvial fans and a new, younger pediment surface at a lower level.
Previous episodes of such regrading is implied by the remnants of an older pediment surface and alluvial fans preserved around Cerro San Ignacio.
Seven plenary meetings are planned in communities most affected by rapid growth on alluvial fans as projected by local governments through 2030.
If we look more broadly in Gale Crater, we can see that there is a prominent feature that geologists call an alluvial fan.
Three alluvial fans within the plain; namely: the Zarub fan in the north, the Moundassah fan in the middle and the Ajran fan in the south (Al-Shamsei, 1993).
Most significant is that all strata in the two successions were deposited in continental environments-mainly fluvial and alluvial fan settings (Nadon 1981; Nadon and Middleton 1985).
In the view to the north, erosion has produced subtle shadings of red and gray, with cream-colored accents spreading out in alluvial fans.
With a little patience, though, during the late fall, winter, and especially spring, spectacular wildflowers may grace the alluvial fans and desert slopes along the Amargosa and Panamint ranges.
Most of the localised recharge happens during summer storms, where ephemeral creeks lose part of their water in the alluvial fans.
The early stretches of this 6-mile round-trip walk provide more of an introduction to the rocky complexity of alluvial fans than you might like.