Flexi Says: The rate of mechanical weathering depends on the type of mechanical weathering and the environmental conditions. For example, ice wedging widens cracks in boulders with each freeze and thaw cycle during winter. Abrasion of boulders with blowing sand wears down rock very slowly over hundreds or thousands of years. The pounding of waves on a sea cliff can produce cracks slowly over time, undercutting the cliff until it gives way and crumbles during one storm event. Tree roots crack rock into smaller pieces over the lifespan of the tree.