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Mass Movements, Wind and Glaciers
Chapter 8 Notes
Mass Movement….
• What factors determine how fast you go down a waterslide?
Mass Movement: Changing the Landscape
• Definition: Movement of soil and rock downslope due to gravity
• All mass movements occur on slopes (i.e. almost everywhere)
• Can be subtle (creep) or catastrophic (landslide) and everything in between
• Range in size from small sediment to large boulders
Factors that influence mass movement
• Climate• Composition of the earth material• Weight of the material• Friction• Triggers (an earthquake, for example)• Water/rainfall: increases weight and
decreases friction
Types of Mass Movements• Creep– Solifluction
(permafrost)
• Flows• Slides• Slumps • Falls
Examples of Mass Movement
Creep Slump
Note the curved crescent shape at the top of the slump.
Examples of Mass Movement
Flows Slides
lahar
Examples of Mass Movement
Avalanche Falls
Wind Erosion
• Moving air can transport sediment– Suspension– Saltation (bouncing motion of sand particles)
• Precipitation limits wind erosion:– Precipitation promotes plant growth that anchors
sediment– Moist soil is not carried as easily by wind
Dust Bowl: Great Plains 1930s
Wind Erosion and Transport
Abrasion Deflation
Desert pavement
Wind Deposition
• When wind velocity decreases, particles are deposited.
• Dunes: piles of windblown sand– Windward side is not as steep as the leeward side– Wind causes dunes to move (“migrate”)
• Loess: Thick windblown silt deposits. – Loess soils are very fertile due to abundant
nutrients and minerals.
Wind Deposition
Loess Dunes
Glaciers
• Large moving masses of ice
• Currently, 10% of Earth’s surface is covered by glaciers
• Can be– Valley glaciers (alpine
glaciers)– Continental glaciers
Valley Glaciers
• Turns V-shaped river valleys into U-shaped glacial valleys
Glacial Erosion
U-shaped valley with hanging stream
Horn
Glacial Erosion
Cirque Arête
Formation of a Cirque
Glacial Deposition
Glacial Deposition
Drumlin
Glaciers in Indiana
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