Question

a block of rocks, soil, and vegetation slowly collapses down a curved surface, leaving a crescent - shaped cliff behind it. what type of mass movement is this?
a. slump
b. earthflow
c. creep
d. rockslide

Explanation:

To solve this, we analyze each option:

• Option A (slump): Slump is a type of mass movement where a block of rocks, soil, and vegetation moves down a curved surface, leaving a crescent - shaped cliff. This matches the description.
• Option B (earthflow): Earthflow involves the flow of fine - grained materials (like silt, clay) downslope, usually in a more fluid - like manner and not leaving a crescent - shaped cliff.
• Option C (creep): Creep is a very slow, almost imperceptible movement of soil and rock downslope, typically due to freeze - thaw or wet - dry cycles, and does not involve the collapse of a block leaving a crescent - shaped cliff.
• Option D (rockslide): Rockslide is the rapid movement of rock masses downslope, often along a planar surface, and does not leave a crescent - shaped cliff as described.

Answer:

A. slump