How fast do geologic processes operate? Do they all work at the same rate? How do the rates of geologic processes compare to the extent of written human history and the rate at which people modify their environment? Include some examples.
There is a great variation in time. As an example a river steadily erodes the land whereas a flash flood can carve a river channel in no time. The rate of erosion also depends on the type of rock. Some rocks such as dolomite are very resistant to erosion while water seeping through limestone forms underground caves as is seen in Florida. It is difficult for us to imagine the Appalachian Mountains once being as high as the Himalayas or the Rockies. These mountains will eventually erode away, leaving nothing but their roots as is found near Georgian Bay. Since I was born the Misssissippi Delta has shrunk because of the straightening of the Mississippi River (Compare a map of today to that of a map printed in the 1950's) Volcanism and earthquakes are also part of the geologic processes, and to us seem to be very rapid changes. In general we don't notice many geologic processes as they occur at a slow rate. As an example none of us will be around 200 million years from now when N America finally collides with Asia, nor will we be around when Niagara Falls retreats to Lake Erie.
