Alluvial Fan


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alluvial fan

[ə′lüv·ē·əl ′fan]
(geology)
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 simulation thickness gradually increases from the top of the alluvial fan to the central basin, and the maximum simulation thickness is 1800 m.
In this area the fault controls a conspicuous relief front that shows a hard calcrete-crust developed over Pleistocene alluvial fan deposits dipping towards northwest.
Surficial patterns of debris flow deposition on alluvial fans in Death Valley, CA using airborne laser swath mapping Geomorphology, v.74, p.152-163, 2006.
The drill hole encountered slightly compact but poorly consolidated Holocene and Pleistocene greenish grey gravelly sand (alluvial fan deposits to 2 meters with a Vs equal to 185 m/s).
Overall, however, the western piedmont is dominated by coalesced alluvial fans generated by innumerable smaller streams that debouch from the uplands (figure 4).
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.
The rounded shape of some stones in the conglomerate indicates long-distance transport from above the rim, where a channel named Peace Vallis feeds into the alluvial fan. The abundance of channels in the fan between the rim and conglomerate suggests flows continued or repeated over a long time, not just once or for a few years.
The rocks in the outcrops were formed when water transported gravels downslope to bottom of alluvial fan, where they remained for some time.
--The resulted gully erosion organisms and the processes of creeping form numerous alluvial fans in our surveyed areas;
indicate the existence of complex processes of change in the landscape of the Pantanal, resulting from the sedimentary dynamic in alluvial fans. In these fan regions the landscape changes continuously because of sedimentation and by avulsion processes.