Drops of rain hit soil and rock and displace grains. When water flows over the surface, it loosens and carries away pieces of rock or soil. There is a tremendous amount of energy in a raindrop. Over days, weeks, months, years, centuries, and millennia, the erosive power of water can cut through even the strongest rocks. The material that the flowing water picks up is eventually deposited when the flow of the stream slows down—this is known as deposition.
Old Faithful in Yellowstone National Park is the most famous geyser in North America. Its eruptions occur so regularly that you can almost set your watch by them.