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alluvial fan

n. A cone-shaped heap of alluvium deposited by a river.

alluvial fan

n. a fan-shaped deposit where a fast flowing stream flattens out [syn: alluvial cone]

Alluvial fan

An alluvial fan is a fan- or cone-shaped deposit of sediment crossed and built up by streams. If a fan is built up by debris flows it is properly called a debris cone or colluvial fan. These flows come from a single point source at the apex of the fan, and over time move to occupy many positions on the fan surface. Fans are typically found where a canyon draining from mountainous terrain emerges out onto a flatter plain, and especially along fault-bounded mountain fronts.

A convergence of neighboring alluvial fans into a single apron of deposits against a slope is called a bajada, or compound alluvial fan.

Usage examples of "alluvial fan".

Tommy yanked the wheel to send the Radio Club van sloughing off the graded road onto the sand and gravel slope of the alluvial fan which spilled from the throat of Avalanche Gulch.

She pushed, and the roiling wall of gas, burning like a sun, swept down the hillside like a great wave, igniting the air as it went, rolling out onto the alluvial fan with a mind-numbing roar to drown out the screams of men and horses standing in its path.

In the few areas where the slope is not exposed rock, but instead is covered with unconsolidated sediment, as in the alluvial fan of the Congo River, we plant the anchors by propellant-actuated embedment procedures.

Consulting my terrain maps of the AO, I conclude that the sediment I landed in first was a portion of the subsea alluvial fan formed by the egress of the Duret River into the Storm Sea, the result of geological ages of sediment carried down from the Kanthurian Mountains and the High Desert Plateau beyond.

It was a strange, isolated place, filled with the mismatched flora of two states: stagnant lakes dotted with dead cypress, solitary oaks in the middle of flat pasture, tangles of blackjack along the edges of coulees, an alluvial fan of sand dunes that were crested with salt grass and from which protruded tall palm trees silhouetted blackly against the sun.

Another vehicle with two other sol-pols sat parked in the flat alluvial fan of a broad wash that looked paler than the surrounding ground.

At this spot on the coast, however, an alluvial fan had been thrust out by the waters of the creek which had cut the ravine to Tommy's right.

They were lurking on a hillside above a playa, where the occasional gullywasher had spewed out a big alluvial fan of desert-varnished grit and cobbles.

A mound of rubbish flowed through it to form an alluvial fan inside the Plaza.

He finally made his way into the dusty alluvial fan at the canyon's mouth, stepping over flattened clay and into the darker shade.