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.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

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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.

Numerical Investigation into the Evolution of Groundwater Flow and Solute Transport in the Eastern Qaidam Basin since the Last Glacial Period

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.

Paleoseismological evidence of Holocene activity of the Los Tollos Fault (Murcia, SE Spain): a lately formed Quaternary tectonic feature of the Eastern Betic Shear Zone

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.

Mapping alluvial areas in semi-arid region of Brazil through collateral data and satellite images/Mapeamento de areas aluvionares no semiarido brasileiro por meio de dados colaterais e imagens orbitais

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).

Equivalent linear earthquake site characterization of layered soil deposits at Shakardarra and Muzaffarabad

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.

Old Streambed on Martian Surface Found

The rocks in the outcrops were formed when water transported gravels downslope to bottom of alluvial fan, where they remained for some time.

Curiosity finds 'concrete' evidence of historical running water on Mars

--The resulted gully erosion organisms and the processes of creeping form numerous alluvial fans in our surveyed areas;

Considerations on the actual geomorphological processes within Valsan catchment-the Steiului and Turnului Valleys sector

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.

Geomorphology and habitat diversity in the Pantanal/Geomorfologia e a biodiversidade no Pantanal