Water Erosion
Moving water has a big part that has shaped Earth's surface. Runoff is water that moves over Earth's surface. The more runoff there is the more erosion there is. The five main factors of runoff are, amount of rain, vegetation, soil, shape of the land, and hoe people use the land. Gravity makes runoff and the materials it contains move downhill. When runoff travels it forms little grooves in the soil called rills. Gullies are large grooves in the soil that carry runoff after it rains. A stream is a channel which water is continually flowing down a slope. A tributary is a river or stream that flows into a larger river or stream. Water erosion start when it rains. Groundwater is what geologists call underground water. When water goes in the ground it mixes with carbon dioxide to from a weak acid called carbonic acid. Carbonic acid can break down limestone. Ground water, erosion, and deposition can create caves in the ground.