Talus

talus (tā`ləs), deposit of rock fragments detached from cliffs or mountain slopes by weathering and piled up at their bases. A talus is a common geologic feature in regions of high cliffs. The angle of slope of a talus is rarely greater than 40°. The constant weathering to which a talus is subjected, which breaks the rock fragments into finer pieces, and the impact of new material being added from above give the base of the talus a tendency to creep and slide. The term talus is often used to refer to the fragments themselves.

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talus [′tal·əs]

(anatomy)

astragalus

(geology)

Also known as rubble; scree.

Coarse and angular rock fragments derived from and accumulated at the base of a cliff or steep, rocky slope.

The accumulated heap of such fragments.

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talus, tallus

1. The slope or inclination of any work, as a talus wall.

2. Coarse rock fragments, mixed with soil, at the foot of a cliff or natural slope.

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Talus 

(talus deposits), drifts formed at the base and on the lower parts of the slopes of elevated areas as the result of the washing out of disintegrated rocks from the upper parts of these slopes by rain and snow water and also because of the force of gravity, frost displacement, and soil movement (solifluction). The products of weathering that constitute talus are varied (from clays and sands to large boulders) and are characterized by weak sorting. In petrographic composition, talus differs from its underlying bedrock, revealing its relation to the rocks that crop out higher on the slope and on the peaks of the elevated areas. Talus is common in mountain areas. Talus deposits on the lower parts of slopes usually form mantle-like covers (talus trains), which soften the transition to the adjacent plain. Talus frequently contains placer deposits of gold, tin, tungsten, and other metals. Talus loams are used in the making of bricks. Academician A. P. Pavlov identified talus as one of the genetic types of continental deposits (1888).

REFERENCES

Pavlov, A. P. “Geneticheskie tipy materikovykh obrazovanii lednikovoi i pozdnelednikovoi epokhi.” Izv. Geologicheskogo komiteta, 1888, vol. 7, no. 7.
Obruchev, V. A. Osnovy geologii. Moscow-Leningrad, 1947.

V. A. GROSSGEIM

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Talus 

an accumulation of rock fragments at the base and on the lower part of a steep mountain slope. Talus forms when rock weathers and fragments roll down a slope. The material is un-sorted and usually consists of angular fragments varying in size from sand grains and chippings to blocks several meters across. The angle of repose of a talus slope is between 30° and 40°, close to the angle of the natural slope. Talus shows differing degrees of stability depending on the steepness of the slope angle.