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Mass Movements, Wind, and Glaciers
Earth ScienceChapter 8
Erosion and DepositionMoving and Changing the Landscape!
Erosion and Deposition
• Erosion: the movement of materials from place to place by the actions of wind, waves, glaciers, gravity, and/or running water.
• Deposition: the laying down of sediments in a new location.
• Each agent of erosion/deposition will produce a variety of unique surface features.
Land erosion
Sand deposition
Agent One: Gravity
Gravity is the force of attraction between two objects. Gravity is influenced by precipitation rates, human interactions, and gradient (steepness of slope). The effect of gravity as an agent of erosion is mass movement. All three examples occur quickly.
SlideBlocks of earth move down slope
landslide
FlowMovement of water rich particles down slope
mudslide
FallPortion of rock move down slope
Rock fall
8.1 MASS MOVEMENTS • Mass movement is the downward transportation of
weathered materials by gravity• Many types of mass movement:– Talus—rock fragments weathered from a cliff that have
“fallen” due to gravity– Landslide—movement of a mass of bedrock or loose soil
and rock down the slope of a hill, mountain, or cliff.• Can be triggered by earthquakes or volcanoes• More prone along steeper slopes• Often follow heavy rains
TYPES OF LANDSLIDES• Creep—slow, imperceptible movement of soil down a slope—causes
poles, fence posts to lean downhill.• Slump—bottom of a slope becomes unable to support the soil at the top
of a slope. The bottom wears away and the top “slumps” downward.• Earthflow—a mass of weathered material that has been saturated with
water flows downhill.• Mudflow—the rapid movement of water that contains large amounts of
clay and silt.– Contain more water than earthflows– Can move over 100 km/hr– Can take out houses, trees, etc.– Often occur in dry regions when they experience extremely heavy rainfall
Agent One: GravityLandslide Landslide
Agent One: GravityCreep
Slow down slope movement of subsoil
Agent One: Gravity
Avalanche
Rapid downhill movement of snownational geo
8.2 Agent Two: WindWind is the movement of air due to the unequal
heating of the Earth’s surface. • Abrasion: • The wearing away of
materials through constant pounding of wind-driven sediments.
• Deflation: • The smoothing of land
caused by the scrubbing of wind-driven sediments.
Agent Three: WavesEmergent Coast
Agent Three: WavesEmergent Coastline
CHAPTER 15: GLACIERS
• Only about 3% of the earth’s water is freshwater and that of that 3%, about 75% is locked up in glaciers.
• A glacier is a large mass of compacted snow and ice that moves under the force of gravity.
• A glacier erodes the earth’s features in one place and redeposits those materials elsewhere.
• Glaciers can form anywhere in the world where there is a snow line. A snow line is the lowest elevation at which a permanent layer of snow exists in the summer.
HOW GLACIERS FORM
• Buried snow becomes compressed and recrystallizes into a rough, granular ice material called firn or ne’ve’.
• Over time, the firn thickens.• The weight of the material at the top compresses the
firn below turning it to solid ice.• Due to the weight, the ice begins to flow downward
or outward.• This moving mass of snow and ice is called a glacier.
TWO TYPES OF GLACIERS
• Valley glaciers—moves within valley walls– Long, slow-moving, wedgelike stream of ice– Also called alpine glaciers– Exist on all continents except Australia
• Continental glaciers—covers a large part of a continent– Occur in areas where all precipitation is snow.– Snow and ice build up and move outward in all directions– Can break off into chunks when it reaches the sea– Greenland glacier—size of Mexico– Antarctica glacier—bigger than U.S. and Mexico combined– A glacier that is less than 50 000 square meters is called an
ice cap.
GLACIAL MOVEMENT AND EROSION
• Some glaciers move only a few centimeters a day while others move over a meter each day.
• This movement erodes rock and land surfaces below the glacier—can even move boulders the size of houses
Agent Four: Glaciers
• Glacier is a large body of ice moving slowly down a valley slope or spreading outward over land.
• There are two types of glaciers- valley and continental.
Continental Glacier
Valley Glacier
Agent Four: Glaciers
• When a portion of the glacier breaks off over a body of water it is referred to as an iceberg.
• Only the melting of continental glaciers causes sea level rise
