Erosion
The carrying away of sediments by moving water, wind, or moving ice is called erosion. Water moving down a river causes much erosion. The river begins as a shallow stream, often high up in the mountains. The water flows downhill and wears away the ground. It dissolves some rocks and picks up sediments from the bottom of the stream. Over time, the stream becomes wider and deeper.
Frozen water also wears down and shapes the Earth's surface features. Thousands of years ago, huge sheets of ice called glaciers helped to shape the rolling plains in the northern United States. They also carved out the Great Lakes.
Glaciers also can push huge amounts along the bottoms and sides of the ice. The sediments grind against the surface below. This grinding carves out hollows in the land.
Ocean waves and flowing water also wear down Earth's surface. Crashing waves break down rock along the coast. Waves drag the sediments back and forth, slowly turning them into sand. Water and sediments pound at narrow sections of land that jut into the water. Such erosion cuts out features called sea caves and sea arches.
The carrying away of sediments by moving water, wind, or moving ice is called erosion. Water moving down a river causes much erosion. The river begins as a shallow stream, often high up in the mountains. The water flows downhill and wears away the ground. It dissolves some rocks and picks up sediments from the bottom of the stream. Over time, the stream becomes wider and deeper.
Frozen water also wears down and shapes the Earth's surface features. Thousands of years ago, huge sheets of ice called glaciers helped to shape the rolling plains in the northern United States. They also carved out the Great Lakes.
Glaciers also can push huge amounts along the bottoms and sides of the ice. The sediments grind against the surface below. This grinding carves out hollows in the land.
Ocean waves and flowing water also wear down Earth's surface. Crashing waves break down rock along the coast. Waves drag the sediments back and forth, slowly turning them into sand. Water and sediments pound at narrow sections of land that jut into the water. Such erosion cuts out features called sea caves and sea arches.
River Valley Formation
Usually a stream joins other streams to become a river. Now there is more water and tumbling rocks. These forces cause more erosion in the river. This erosion may carve out a steeper or wider river valley. Sometimes, fast cutting of the valley floor in the upper part of the river can form a canyon.