Landslides

The slopes above streams and rivers are subjected to a variety of processes that cause them
to recede and retreat from the river or stream channel. These processes, collectively called
mass wasting, can be classified according to rapidity of movement and according to the type
of materials that are transported. Gravity is the force behind all such downslope movement.
Factors that enable the force of gravity to overcome the resistance of inertia and friction
to move more material downslope include: saturation by water which acts as a lubricant,
steepening of slopes by streams, waves, or road construction, alternate freezing and
thawing, and earthquake vibrations. Mass wasting of surface material is widespread process
that can be found in high mountains, desert hillsides, deep ocean shelves, steep ocean shores
and even on the moon and other rocky planets.