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Ch 10 Mass Movement - Coggle Diagram
Ch 10 Mass Movement
Flow
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C) MUDFLOWS
Most extreme. 30% water. They can reach 80 km/hr. Have energy to carry boulders as big as houses. A laher is a deadly form of mudflow and associates with volcanic avtivity. Example columbis 1985
A) EARTHFLOW
Saturated slope downhill. Occurs on hillsides and valley sides. Common where regolith lies on impermeable rock. If flows are short they produce small bulges and if they break vegetation they leaves scars on the landscape. They block roads and railways.
B) BOGBURSTS
Peat becomes saturated and moves downhill. Example Derrybrien, Slieve Aughty Mountains 2003. Triggered by construction. Peat dried + contracted and lost grip on bedrock. Peat became liquid. Uprooted trees, blocked roads and damaged property.
Solifluction
melting of permafrost. eg Northern Canada. The ground below the surface is frozen and the top layer is thawing. Meltwater cant seep down and the top layer becomes soggy mix of vegetation and water. If this occurs on a slope it will run downwards leaving bulges on the soil - SOLOFLUCTION LOBES
Landslide
A) SLUMPS
Slope base has been removed by human activity
Common in the North Antrim Coast.
Rocks such as basalt present a steep cliff along the coastline.
Underlying rock is easily eroded.
Sudden and rapid downward movement of material and move up to 300 km/hr.
Water eases the movement of regolith. Occurs where there are weak layers of rock, earthquakes, weathering and human activity.
Common in Hong Kong
B) ROCKSLIDES Occur along bedding planes. Occurs when materials in fractures and materials move downslope. Water can ease the movement.
Vaiont Reservoir
Occurred in nothern Italy in 1963. Water saturated clay and began to move downward.
After 10 days of rain and rate increased. 200 million tonnes slid into the reservoir at 100 km/hr
Killed 2600 people
Falls
A) ROCKFLOW Rapid. Freeze that enlarges cracks breaking rocks which gather on the ground as scree. Cutting waves create over hang . can also happen due to human activity. A covering of mesh wire to trap rocks as they fall Example Skellig Michael
B) AVALANCHE
Mass of snow and ice falling . The falling snow pushes the air ahead of it as strong avalanche wind. Snow is loose and unstable and a weak layer can collapse due to things such as earth tremor, human activity or thawing.
Meltwater seeps through crack . Snow spills downslope as an avalanche. It may occur when a small earthquake hits a snow covered region or weight can be too much eg a snowboarder.
Approx. 100 people in the Alps die each year.
Solution Artificial avalanches are the best method of controlling avalaches.
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Soil Creep
Slowest type. Involves movement of downslope of regolith. It moves at a rate of 0.5cm per year. Produces terracettes. Vegetation slows down movement.
Evidence Trees and telegraph tilted
Freeze Thaw Cycle - Water freezes between grains and expands by 9%. As it melts it pulls grains down and forward.
Wet Dry Cycle - Grains absorb moisture. They expand and move upwards. When they dry, they contract. The grains move down and forward.
Factors affecting
Gradient - Steeper the slope more likely and faster it will be.
Slope Material - If material is consolidated less likely of mass movement.
Earthquakes - Increases chances.
Water Content Water acts as a lubricant and controls speed.
Vegetation Cover - Contributes to stability of slopes.
Human Activity - Deforestation, overgrazing, construction, traffic.