Question

which phrase provides the best definition of mass movement?
the movement of material caused by erosion
the slow flow of a glacier as it moves through the valley of a mountain
the movement of large amounts of soil and rock debris down a slope
the fast movement of a boulder rolling down a slope

Explanation:

Mass movement refers to the movement of large amounts of soil and rock debris down a slope. Erosion is a separate process. A glacier's slow flow is glacial movement. A single boulder's movement is not mass movement.

Answer:

the movement of large amounts of soil and rock debris down a slope