External Forces that Shape Earth: Weathering
• Weathering: processes that change the characteristics of rock
• Creates sediment, or small pieces of rock (mud, sand, silt)
Sandstone hills on the Utah-Arizona border
Types of Weathering
Mechanical• Changes SIZE or SHAPE• Ex. Rocks splitting due to
ice or tree roots
Chemical• Changes COMPOSITION• Ex. Iron rusting, damage
caused by acid rain
External Forces: Erosion• Material is moved by wind, water, ice or
gravity• Reshapes landforms, coastal regions and rivers
Water Erosion
• Can be vertical or horizontal- streams can become deeper & wider
• Creates V-shaped valleys• When a river empties
into an ocean, it deposits sediment in a fan-like landform called a delta
• Examples: waves changing the coastline, Grand Canyon
Nile River Delta
Wind Erosion• Dust storms can carry
6,000 tons of sediment per cubic mile of air
• May produce new landforms
• Loess- wind blown silt & clay sediment that becomes fertile soil
Arizona
Glacial Erosion
• Glaciation is the changing of landforms due to glaciers
• Creates U-shaped valleys