•The key to erosion is something called "fluid flow." Water, air, and even ice are fluids because they tend to flow from one place to another due to the force of gravity. Of the three, liquid water...
Gravity is my guess because gravity pulls down on water making it run downhill.Ice can't be because ice moves "slowly" across the land. Wind can't be it either because the wind can land the sediment...
The Earth's gravitational pull on the ice in a glacier forces it to flow like a river (but much more slowly). As it does so the hard lower surface of the ice grinds away at the rock...
by wind erosion the soil is carried by the wind. as in a storm, the soil is carried by the wind. by water erosion the soil is carried by the water. as in high tides the soil is taken by the water...