D1-2
Erosion and Deposition
The erosion action of the water at Victoria Falls in Africa has resulted in the formation of a series of deep gorges downriver from the falls.
The two major external processes that shape the physical features of the Earth are weathering (see lesson C4 – Weathering and Soil Formation) and erosion.
There are four major agents of erosion. These four agents are:
These four agents of erosion will eventually drop the rock and soil sediment that they are carrying. This process is called deposition.
Did You Know?
The High Cost of Soil Erosion
The erosion of soil can have serious environmental costs. It is estimated that during the last 40 years, nearly one-third of the world’s arable (farmable) land has been lost to erosion.
Try This!
The brown color of the water at the mouth of the Atchafalaya River in Louisiana is due to the presence of eroded soil.
A River Runs Through It
The action of running water in rivers is a major agent of erosion.
The Local Scene:
- Locate the nearest river to where you live and zoom in on it.
- What is the name of the closest river to you? Answers will vary depending on location.
- Follow this river until it empties into a major body of water.
- Into which body of water does the closest river to you empty? Answers will again vary depending on location of closest river.
The North American Scene:
In this section you will locate the six longest river systems in North America.
- Complete the table below by following each river to determine what major body of water lies at its mouth. (Click on each river’s name in order to travel to its location.)
| River System | Length | Body of Water at Mouth |
| Mississippi (including Missouri) |
6,275 km (3,902 miles) | Gulf of Mexico |
| Mackenzie (including headwaters of Peace and Finlay) |
4,241 km (2,637 miles) | Arctic Ocean |
| Yukon | 3,185 km (1,980 miles) | Bering Sea (Pacific Ocean) |
| St. Lawrence (including Niagara, Detroit, St. Clair, St. Marys and headwaters of St. Louis) |
3,058 km (1,900 miles) | Atlantic Ocean |
| Rio Grande | 3,057 km (1,900 miles) | Gulf of Mexico |
| Nelson (including headwaters of Saskatchewan; North and South Saskatchewan) |
2,570 km (1,597 miles) | Hudson Bay |