Erosion and Deposition ► The process that wears away surface materials and moves them from one place to another is called erosion. ► Causes of erosion -1. Gravity -2. Water -3. Wind -4. Glaciers ► Gravity is the force of attraction that pulls objects towards Earth’s center. ► Agents of erosion drop the sediments as they lose energy. This is called deposition. ► When sediments are eroded, they are not lost, they are just relocated.
Mass Movement ► Any type of erosion that happens as gravity moves materials down slope is called mass movement. ► Some happen very slowly, others happen quickly and cause catastrophes. ► When a mass of material slips down along a curved surface, the mass movement is called a slump. This can be caused by water weakening the mass, or if a strong rock layer lies on top of a weak rock layer, commonly clay. A curved scar is left where the slumped materials originally rested.
Creep ► Creep occurs where sediments slowly shift their positions downhill. ► Leaning trees and human-built structures, such as houses show evidence of creep. Creep is common in areas of frequent rainfall and snowfall.
Mass Movement Cont. ► Rock falls happen when blocks of rock break loose from a steep slope and tumble down, causing more and more rocks to crash into each other and break loose. -This can be caused when water freezes in rocks and the cracks expand. ► Rock slides occur when steep layers of rock slip down slope suddenly. -Rock slides are common in mountainous areas or areas with steep cliffs. They can occur after heavy rains or during earthquakes.
Mass Movement Cont. ► Mudflows occur in areas that have thick layers of loose sediments. -These happens after vegetation has been removed. -When heavy rains fall on the area, the water mixes with sediments causing it to be thick and pasty. -Gravity causes the mass to flow downhill, where it loses energy and deposits everything it has been carrying.
Consequences of Erosion ► People live on steep slopes because they like to have a great view and live in scenic areas. ► When people build homes on steep slopes, they make slopes steeper or remove vegetation. This speeds up erosion.; ► One of the best ways to reduce erosion is to plant vegetation. ► Drainage pipes can help prevent water from building up. ► Walls or boulders can reduce soils erosion by holding soil in place. ► Eventually, regardless of time and money spent to preserve land, gravity always wins.