In 1973, part of the flat ground on which a subdivision was located became saturated and began to flow toward the Saint Lawrence River at speeds of up to 26 kmph (16 mph). The ground that flowed consisted of silts and clays-not large, rocky regolith. What type of mass wasting event was this?
A) debris avalanche
B) soil creep
C) Earth flow
D) lahar

Question

Quizplus · Accepted Answer

The fact that the ground was comprised of silts and clays and flowed at a relatively slow speed indicates that this was likely an earth flow. A debris avalanche would require larger, rocky material and typically moves at much higher speeds. Soil creep involves a slow movement of soil downhill, whereas a lahar is a type of mass wasting event specific to volcanic areas involving a mixture of volcanic ash and water.

In 1973, Part of the Flat Ground on Which a Subdivision