Mass Movement, Wind, Glaciers

Mass Movement 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  

MaSS mOVEMENT Too little H2O does not stop material’s potential mass movement. Increase H2O, weight of material increases and acts like a lubricant. With the force of gravity , mudslides. H2O moves with material. It is not a transport agent.  

Types of Movements 1. Creeps 2. Flows 3. Slides 4. Slumps 5. Avalanches 6. Rockfalls

Creep 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.  

Creep

Flows Flows - materials flow as thick liquids. Speed - few cm’s per year to 100’s km per hour. Swift mixtures of mud and H2O. Trigger - earthquakes, volcanic eruptions heat the earth. Common in sloped, semi arid regions - short rain storms - ex. LA Basin  

Flow

Slides 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.

Slide

Slumps 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.

Slump

Avalanches 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.

Alvalanche - Swisszerland

Rock Falls 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.  

Rock Fall

Comparison of all Mass Movements

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.

Trenches along Roads

Protective Netting

Heavy Gauged Fences

Retaining Wall

Wind 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.

Methods of Transportation 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

Mechanics of Saltation

Dry moving sand (light color) is visible by streamers

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.

Deflation 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  

Deflation

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

Ventifact

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

Dunes 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  

Types of Dunes

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

Desert Pavement near Blyth CA

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

    Glaciers They shape the landscape by: a) eroding b) transporting c) depositing huge volumes of rock and sediments  Today, scientists measure movements and size changes of glaciers to track climate change.    

MOVING Masses of Ice 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.

Glacier Classification 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.

Valley Glaciers

Continential Glaciers 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.  

Continential Glacier

Glacier Erosion    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.  

Glacier History 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

cirques

ARETE

HORN – Mt. Kimmel Glacier National Park

HANGING VALLEY

WATERFALLS - Yellowstone

U SHAPED VALLEYS

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

Moraines glacier forming a Cirque

Outwash 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.  

Outwash Plain

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

Glacier LAKES 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.  

Glacier Lake

Kettle Lake