The Grand Canyon

The Grand Canyon in Arizona was carved out of the Earth by erosion. Erosion is the process by which weathered rock and soil are moved from one place to another. Erosion carries away the products of weathering.

Deposition is the process by which sediments are laid down in new locations.

Both erosion and deposition change the shape of the Earth’s surface. The agents of erosion are gravity, wind, glaciers, waves, and running water. (An agent of erosion is a material or force that moves sediments from place to place.)

Gravity pulls rock and soil down slopes. The downhill movement of sediments is called mass wasting. Gravity

Landslide Creep Slump Mudflow Examples:

Wind is the most active agent of erosion in deserts, plowed fields, and beaches. Deflation-wind removing loose materials Abrasion-rock particles wearing away rock Wind

Faster wind carries more particles, slower wind carries less particles. Sand Dune-mound of sand deposited by wind (feature of beach area). They protect areas away from the ocean from further erosion. Wind

Loess - many layers of fine sand and silt deposited in the same area (parts of the Mississippi River Valley) Wind

A glacier is a large mass of moving ice and snow. Glaciers move very slowly through valleys and down mountains. Glaciers

Others are formed in polar regions (continental glaciers or icecaps). Glacial ice erodes by abrasion and by plucking away the rock beneath it. Glacial erosion changes V-shaped valleys into U-shaped valleys. Glaciers

Till - Rocks and debris deposited directly by a glacier.

Till varies in size from from large boulders to fine clay particles.

When a glacier melts and retreats it leaves behind till that forms a ridge called a moraine.

Rocks can be carried great distances by glaciers. A drumlin is an oval-shaped mound of till. When valley glaciers stop advancing, melting ice forms streams that flow out from the glacier called melt-water streams. A kettle lake is formed b a block of ice left by a glacier.

Waves

The powerful force of waves constantly erodes and shapes the shoreline. As breaking waves hit the shoreline, the force of the breaking waves knocks fragments off the rock.

Waves can also cause erosion by forcing water into cracks in the rocks, which builds up pressure breaking the rocks over time. The chemical action of salt can also break down rocks.

Sea stacks are columns of rock left standing when cliffs are eroded away.

Sea caves are hollowed out parts of sea cliffs. Waves carry large amounts of sand, rock particles, and pieces of shells. At some point, waves deposit the material they carry.

Running Water

Running water is the major cause of erosion. Rivers, streams, and runoff are a form of running water. As water and sediments move downhill, they cut into the soil and form grooves called rills.

Rills get deeper and wider. Gullies form (channels for runoff)

Amount of runoff is affected by: rainfall in an area amount of plant growth shape of the land

Lots of gullies coming together forms a stream. Streams carry large amounts of sediments. Soil and rock particles carried by a stream are called a load. Streams cause erosion by abrasion.

If a stream falls over hard rock and then soft rock a waterfall will form. Streams join to form rivers.

A network of rills, gullies, streams, and rivers is called a drainage basin.

Large streams called tributaries flow in the main river.

The river empties into another river, lake, or ocean which is called the mouth of the river. The area drained by a main river and its channels is called a drainage basin. Land that separates on drainage basin from another is called a divide.

One of the largest is the Continental Divide in the United States.

An immature river is a young river in its early stage of development. Its valleys are V-shaped, and the river covers the entire valley floor.

Mature rivers have been developing for thousands of years. They have few rapids and waterfalls due to so much erosion, their valley walls a far from the river, the valley itself is broad and flat, and the course of the river has become curved and winding, forming loops called meanders.