Process:  -When water freezes it becomes 10% bigger, or takes up 10% more space -As water expands it puts great pressure on the walls of anything containing it, including any rocks which happen to be surrounding it -The force of the pressure exerted on the rock surrounding it is enough to wedge the walls of the crack farther apart, thus expanding and deepening the crack -Clay expends when wet like ice does -This causes rock to break apart -Some plants like mosses and lichens are capable of growing without soil on bare rock -When they do this their roots penetrate pores and crevices and cause rocks to split apart as the roots force their way down through the rocks -
 Question: What is the effect of increased automobile use on less or slower erosion of rocks.?
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