Most geologic erosion occurs over short periods of time, via storms, floods, earthquakes, etc. Otherwise erosion occurs at a more or or less steady slow rate.
Re: Most geologic erosion occurs over short periods of time, via storms, floods, earthquakes, etc. (quoting myself)
I left out landscape sculpturing by glaciers. Not exactly a rapid process, but glaciers do remove a LOT of material as they grind through bedrock and plow away sediment and rubble. They are responsible for many deep u-shaped valleys throughout the world.
Sometimes major fall events happen without any of these factors being present. Erosion from running water and repeated freeze/thaw cycles fractures and weakens rock over long periods of time, setting up conditions for major fall events. You have to eliminate that before you can attribute it exclusively to the concurrent events.