Question

A relatively rapid form of mass movement that is most common in dry mountainous regions is _____.

Answer 1

The answer to your question is a mudflow

Answer 2

The right option is; a mudflow  

A relatively rapid form of mass movement that is most common in dry mountainous regions is a mudflow.  

A mudflow is a rapid moving mass of soil that has been made fluid by the addition of considerable amount of water (from rain or melting snow) to the source material. Mudflows usually begin as slides and later become flows when water joins it along the flow path. The major component of mudflows is clay and they are usually found in dry mountainous areas.