Earth Science: Chapter 9 - Erosion and Deposition
The Big Idea: Processes on Earth’s Surface
How do erosion and deposition change Earth’s surface?
- Erosion and deposition by mass movements of flowing water, ice, waves, and wind wear down and build up the land.
Changing Earth’s Surface
- Weathering, erosion, and deposition act together in a cycle that wears down and builds up Earth’s surface.
- Gravity causes mass movement, including landslides, mudflows, slump, and creep.
- Moving water is the major agent of the erosion that has shaped Earth’s land surface.
- Through erosion, a river creates valleys, water-falls, flood plains, meanders, and oxbow lakes.
- Deposition creates alluvial fans and deltas. It can also add soil to a river’s flood plain.
- Groundwater can cause erosion through a process of chemical weathering.
The Force of Moving Water
- As gravity pulls water down a slope, the water’s potential energy changes to kinetic energy.
- Most sediment washes or falls into a river as a result of mass movement and runoff.
- A river’s slope, volume of flow, and the shape of its streambed all affect how fast the river flows and how much sediment it can erode.
- There are two kinds of glaciers:
- continental glaciers
- valley glaciers
- Glaciers can form only in an area where more snow falls than melts. Once the depth of snow and ice reaches more than 30 to 40 meters, gravity begins to pull the glacier downhill.
- The two processes by which glaciers erode the land are plucking and abrasion.
- When a glacier melts, it deposits the sediment it eroded from the land, creating various landforms.
- The energy in waves comes from wind that blows across the water’s surface.
- Waves shape the coast through erosion by breaking down rock and transporting sand and other sediment.
- Waves shape a coast when they deposit sediment, forming coastal features such as beaches, spits, and barrier beaches.
- Wind causes erosion by deflation and abrasion.
- Wind erosion and deposition may form sand dunes and loess deposits.