Correct option is B
Introduction
Mass movements are classified by the speed of the moving material. A
Rock-fall is a form of very rapid mass movement where individual rocks or a mass of rock detach from a steep slope or cliff face and fall freely, bounce, or roll down. This free-falling action makes it the
fastest type of mass movement.
Information Booster
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Mass Movement: A process where material moves down a slope under the influence of gravity.
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Speed:
Rock-fall is the
fastest type of mass movement.
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Mechanism: Detached rocks fall through the air with little or no interaction with other materials on the cliff face.
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Slope: Occurs almost exclusively on very steep or vertical cliff faces.
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Contrast: Other movements like creeps (slowest), slumps, and slides are much slower than free-falling rock.
Additional Points
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Rock-slide and
Debris-slide: These are movements where the rock or debris slides along a relatively well-defined plane; while fast, they are generally slower than a free-fall.
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Rock-slump: A form of rotational slide that is slower than a rock-fall, characterized by a backward rotation of the moving mass.