Fact 1: Rocks interacting with wind over long periods of time causes weathering.

Fact 2: Winds grind down rocks.

Given the two facts above, answer the question "What grinds rocks over time?" with the following options: 
- deltas
 - erosion
 - Time and energy
 - weathering
 - Echinoderm.
 - deuterostomes
 - amoebae
 - bullfrogs


 

    weathering     