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1.  A down slope movement of loose sediment and weathered rocks resulting from the force of gravity.  Erosion following weathering climatic conditions.

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Presentation on theme: "1.  A down slope movement of loose sediment and weathered rocks resulting from the force of gravity.  Erosion following weathering climatic conditions."— Presentation transcript:

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2  A down slope movement of loose sediment and weathered rocks resulting from the force of gravity.  Erosion following weathering climatic conditions determine which materials and how much  All mass movements occur on slopes  Several variables influence mass movement  1) Material weight result from gravity  2) Materials resistance to sliding or flowing  3) Trigger ie. Earthquake  4) Water  Movement occurs when a force works and pulls materials is the stronger than its resistance  Erosion and undermining soil increases the materials pull down of the slope  2

3  Too little H 2 O does not stop material’s potential mass movement.  Increase H 2 O, weight of material increases and acts like a lubricant. With the force of gravity, mudslides.  H 2 O moves with material. It is not a transport agent. 3

4 4  1. Creeps  2. Flows  3. Slides  4. Slumps  5. Avalanches  6. Rockfalls

5  Creep - slow/steady flow of loose weathered material.  Noticed over a long period of time. Indication - tilt of structures.  The slow, downhill movement of loose, water-logged materials that occurs in regions of permafrost is called solifluction. 5

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7  Flows - materials flow as thick liquids. Speed - few cm’s per year to 100’s km per hour.  Swift mixtures of mud and H 2 O. Trigger - earthquakes, volcanic eruptions heat the earth.  Common in sloped, semi arid regions - short rain storms - ex. LA Basin  7

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9  Slides - Rapid downward movements of earth materials that  occur - landslides - speed 200 km per hour. Stop at the bottom of slope as debris piles. Common - steep slopes.  Rockslides - type that occur when a sheet of mud moves down hill on a sliding surface. Trigger - Earthquakes. 9

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11  A slump is a mass of material in a landslide that rotates along a curved surface.  Locations of slumps are in areas of thick soil on moderate to steep slopes and highways.  Common after rain, reduces friction, forces between the center of the soil.  Slumps leave crescent shaped scars on the slope. 11

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13  Avalanches - Landslides that occur in mountainous areas with thick accumulation of snow. - slopes 35°.  10,000 avalanches occur in U.S. Sun melts the snow.  It reflects/ more snow added weight causing breakoff. 13

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15  Rockfalls - Occur at high elevations in step road cuts and on rocky shores.  Physical weathering process - breakdown - rock - rock falls straight down.  Human Factor - affect mass movement construction - heavy building - roads- weight helps makes slopes unstable. Leakage/septic tank seaps around. 15

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18  Catastrophic mass movement - most common on slopes greater than 25° with annual rainfall of over 90 cm.  Preventative action for land movement: trenches along roads to catch debris; protective fencing; steel netting along slopes; retaining walls. 18

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23  Wind transports material up hill and down erosional agents that are modified, ie. wind changes the landscapes in arid and coastal regions.  Ability to move material as less than H2O and ice.  Wind transports materials causing them to move different ways. 23

24 Strong winds - carry long distance (suspension) Saltation - Bounding motion of particles, ie. sand wind transport occurs in areas with little vegetation, ie., desserts, some arid areas, seashores and lakeshores 24

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27  Wind transports material up hill and down erosional agents that are modified, ie. wind changes the landscapes in arid and coastal  regions.   Ability to move material as less than H2O and ice.   Wind transports materials causing them to move different ways.  27

28 Deflation - lowering of the land’s as surface result of movement. Problem - agriculture regions: 1930’s Dust Bowl - Sever dust storms - clouds of dust blown by the wind create deflation blowouts - shallow depressions 28

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30  Abrasions - when particles such as sand rub against the surface of rocks and other materials. Rocks shaped by wind blown sediments are called ventifacts. 30

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32 32 Occurs in arid regions of change in wind velocity. Particles drop out of the air to the ground

33 Formation of Dunes - sand accumulates from the dropping of wind. A dune is a pile of wind blown sand. Conditions necessary for formation of dunes: 1) Availability 2) Wind velocity 3) Wind direction 4) Amount of vegetation 33

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36  Desert Pavement - when finer sediments are blown away by wind and the heavier larger particles and pebbles are left behind.   Tallest dunes - Sands in Arabia - more than 100m in height   Quartzs Sand - most common   Gypsum Dune - white sand - National Monument in New Mexico   Calcite Dune - Bermuda and areas of the Caribbean Sea  36

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38  Loess - wind carries fine, lightweight particles, ie. Clay and silt   Loess deposits - Illinois, Iowa, Missouri, South Dakota, Nebraska 38

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40  Glacier – a large moving mass of ice.  Formed near the earth’s poles and at high elevations in the mountains.  They cover only 10% of the earth. 40

41  Classified in two ways:  1) Valley Glaciers - form in valleys in high mountainous areas, occurs when growing ice mass becomes too heavy to maintain its rigid shape and begins to flow.  Flow begins when the accumulation of snow and ice exceeds 20 meters in thickness. 41

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43  2) Continental Glaciers - cover broad, continent sized Areas.  They form under the same climatic conditions as valley glaciers, but move in a different way.  The weigh of this glacier forces it to flatten is all directions.  These glaciers are also called ice sheets. 43

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45  Of all erosional agents, glaciers are the most powerful because of their great size, weight, and density when a valley glacier moves, it breaks off pieces of rock through a process called plucking.  When glaciers with embedded rocks move over bedrock valley walls, they grind out parallel scratches into the bedrock.  Small Scratches are called striations, larger ones are called grooves.  45

46  Scratches and grooves provide evidence of a glacier’s history and establish its direction of movements.  Glacier features include:  1) cirques - deep depressions  2) arete - where two cirques on opposite sides of a valley forming a sharp, steep ridge.  3) horn - glaciers on three or more sides of a mountain top, a steep, pyramid shaped peak forms. Ex. Switzerland’s Matterhorn  4) hanging valley - tributary valley that enters a U- shaped valley from high up a mountain side  5) waterfalls  6) U-shaped valleys 46

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54  Glacial till is the mixed debris that glaciers carry.  Moraines are ridges consisting of till deposited by glaciers. 54

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56  It is melt water contains gravel, sand, and fine silt formed by the grinding action of the glaciers of the glacier.  When this sediment is deposited by melt water, it is called out-wash.  The area at the leading edge of the glacier, where the melt water streams flow and deposit outwash, is called an outwash plain. 56

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58  Glaciers that move over older moraines and forms the materials into elongated land forms called drumlins.  58

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60  Glacial Lakes - Sometimes a large block of ice breaks off a glacier and is later covered by sediment.  When the ice block melts, it leaves behind a depression called a kettle hole. After the ice blocks melts, the kettle hole fills with water from rain and runoff. 60

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