When material on a hillside has weathered (the process described in chapter 19), it is likely to move downslope because of the pull of gravity. Soil or rock moving in bulk at Earth's surface is called mass wasting. Mass wasting is one of several surficial processes. Other processes of erosion, transportation, deposition - involving streams, glaciers, wind, and ocean waves - are discussed in following chapters.
Landsliding is the best known type of mass wasting. Landslides destroy towns and kill people. While these disasters involve relatively rapid movement of debris and rock, mass wasting can also be very slow. Creep is a type of mass wasting too slow to be called a landslide.
In this chapter, we describe how different types of mass wasting shape the land and alter the environment and what factors control the rapidity or slowness of the process. Understanding mass wasting and its possible hazards is particularly important in hilly or mountainous regions.
