Erosional Forces
Chapter 7
Gravity
Section 7.1
Erosion and Deposition
Describe the relationship between weathering, erosion and deposition.
Erosion and Deposition
Weathering rock broken up into smaller pieces
Erosion these smaller pieces are moved
Deposition these moving pieces stop moving
WEATHERING EROSION DEPOSITION
Erosion and Deposition
What are the agents of erosion?
Erosion and Deposition
Agents of Erosion
Gravity
Ice (glaciers)
Wind
Water
Erosion and Deposition by Gravity
What do we call erosion by Gravity?
Erosion and Deposition by Gravity
Erosion by Gravity Mass Movement
Erosion and Deposition by Gravity
What are some examples of Mass Wasting?
Erosion and Deposition by Gravity
Slump - lose materials of rock layers slip down a slope
Underlying material will not support the sediment above
Water and mud underlying material
Curved scar is left
After earthquake or prolonged rains
Erosion and Deposition by Gravity
Creep sediments slowly inch down a hill
Leaning trees and poles
Common in areas of freezing and thawing
Erosion and Deposition by Gravity
Rockslides large blocks of rock fall down a steep slope
After heavy rain or earthquakes
Freezing and thawing break loose rocks
Rocks knock other rocks down at anytime
Erosion and Deposition by Gravity
Mudflow thick mixture of water and sediment
Occur in relatively dry areas
Cone shaped deposit at bottom of the hill
Mass Movement
Glaciers
Section 7.3
Continental and Valley Glaciers
What is a glacier?
Continental and Valley Glaciers
Glacier moving mass of ice and snow
Continental and Valley Glaciers
What are the two types of glaciers?
Continental and Valley Glaciers
Two types of Glaciers:
Continental
Valley (alpine)
Continental and Valley Glaciers
Continental Glaciers
Large
Ice age 28% of earth covered by glaciers
Today 10% of earth covered by glaciers
Mostly near poles
Greenland
antarctica
Continental and Valley Glaciers
Valley Glaciers
Can occur in warm climates at high altitudes
Build up in winter and melt back in summer
Glacial Erosion
Examine map on pages 504 505.
Glacial Erosion
Identify the position of the continental shelves
Glacial Erosion
During the last Ice age sea level was 137 meters ( 1 ½ football fields) lower than it is now.
Glacial Erosion
Where do you think the shore line of North America would be if the glaciers in Antarctica and Greenland were to melt?
Glacial Erosion
What is a cirque and how does it form?
Glacial Erosion
A cirque is a bowl-shaped basin that is created in the side of a mountain where glacial plucking has occurred. Often a cirque forms where a glacier begins.
Glacial Erosion
How does plucking occur?
Glacial Erosion
Glacial snow and ice melt and flow down into cracks in rocks. When the water refreezes in these cracks, it expands and breaks the rock into pieces.
Glacial Erosion
What are grooves?
Glacial Erosion
Long parallel scars scraped into rocks by glaciers
Glacial Erosion
What causes a mountain horn?
Glacial Erosion
A mountain horn forms on mountain peaks that have been glaciated. Three or more cirques have scoured out the rock and left fairly sharp ridges between the cirques.
Glacial Deposition
What is Till?
Glacial Deposition
Till mixture of different sized sediments that are deposited when a glacier slows down or stops.
Glacial Deposits
What is Outwash?
Glacial Deposition
Outwash Material deposited by the meltwater from a glacier
Heavy deposits close to glacier
Lighter deposit further away
Outwash plain
Glacial Deposition
What is the difference in a valley cut by a glacier and a river?
Glacial Deposition
River V-shaped
Glacier U-shaped
Wind
Section 7.4
Wind Erosion
What is Deflation?
Wind Erosion
Deflation small loose sediment is removed by wind leaving behind larger particles
Wind Erosion
What is Abrasion?
Wind Erosion
Abrasion wind blown sediments strike surfaces and break of pieces
Wind Erosion
Sand Storms occur when wind is strong enough to pick up larger particles of sand.
Wind Erosion
Dust Storms occur in dry areas where soil is loose.
Reducing Wind Erosion
What are some methods to reduce Wind Erosion?
Reducing Wind Erosion
Methods to reduce Wind Erosion:
Windbreaks line of vegetation(trees) to slow wind
Roots - plant roots hold soil together
Deposition by Wind
What are some examples of Wind Deposits?
Deposition by Wind
Wind Deposits:
Loess - very fine deposits of wind blown sediments, sometimes deflated from glacial outwash areas
Dunes Build up of sediment against an obstacle
Deposition by Wind
How do Dunes move?
Deposition by Wind
Dune Migration
Wind blows from the windward(side wind is blowing from) side of an obstacle
Sediments build up on the leeward(opposite side wind is blowing from) side because wind speed is less
Wind picks up sediment on windward side and deposits it on the leeward side causing the dune to move
Windward side gentle slope
Leeward side steep slope
