Falling rocks are common in mountainous areas. Cracks (or joints) in bedrock
allow rain water or snow melt to seep in then freeze into solid ice, which in
turn expands and widens the cracks over time. Not a one time event, the freezing
and thawing takes place continuously as the warmth of sunlight thaws ice then
the colder nights freeze the water once again. This freeze/thaw cycle is common
in mid-latitudes. The process is called frost action (also known as frost wedging).
Eventually the cracks become so large and deep that they compromise the integrity
of the bedrock, loosening large chunks that eventually fall to the base of the
mountain.
Is this fallen rock an example of weathering or erosion?
