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 ?
Within the walls of Acopios 1 and Acopios 2 a high angle (subvertical), south-dipping fault zone affecting alluvial fan deposits can be seen (Figs.
The Urao lake shows a transition from the alluvial fan deposits in the northern margin of the basin towards the fine clay deposits of the lake centre.
When we look at the location of the Curiosity landing site with respect to the alluvial fan we can see that the rover landed downstream of the 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).
Accumulation processes have a lower manifestation, especially, in creeks confluence area with the Valsan river mouth and its tributaries valleys as alluvial fan.
It features a depositional tract of sandy sediments derived from the plateaus of sedimentary basins, forming huge alluvial fans and lacustrine and fluvial environments.
The alluvial fans and hillsides had some difficulties for crop production, because the streams can sweep the soil instead of depositing it; furthermore, the streams can change their course over the alluvial fan from one year to another.
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).
The gentle alluvial fan of the Preak Tnaot was also generally not inundated, except for its low-lying eastern skirt (within Phnom Penh city).
Alluvial fans develop where the stream trunk enters the "Delta" as these streams lose their energy and their bed load.
Two research groups of the Geological Society of London claim that they chose Sorbas, in southeastern Spain as the cite for 2003 a conference on alluvial fans because it is a tectonically active dry region with a wide range of Quaternary alluvial fans.