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