Erosion and Deposition n Erosion wears away surface materials and moves them from one location to another. n Agents of erosion are: gravity, glaciers, wind, and water. n Deposition is the dropping of sediments.

Erosion and Deposition by Gravity n Mass Movement: when gravity alone causes materials to move down-slope. n Slump n Creep n Rockslide n Mudflow

Slump n A mass movement that happens when loose materials or rock layers slip down a slope. n Happen most frequently after earthquakes or heavy rain

WINTER PARK, FL, SINKHOLE

Creep n Sediments slowly inch their way down a hill. n Common in areas of freezing and thawing.

Rockslide n Large blocks of rock break loose from a steep slope and start tumbling. n Happen most often after earthquakes or heavy rain, but can happen at anytime without warning.

SHALLOW SOIL SLIP

Mudflows n A thick mixture of sediments and water flowing down a slope. n Happen in dry areas where sediments have accumulated and heavy rain begins to fall.

LANDSLIDE BLOCKS THE CANYON FLOODING COMMUNITY OF THISTLE, UTAH BY CREATING A NATURAL DAM.

VAIONT DAM IN ITALY, 2600 LIVES WERE LOST WORLD’S WORST DAM DISASTER, OCTOBER 9, 1963

Glaciers n A moving mass of ice. n Continental and Valley n Continental glaciers cover large amounts of land. n Valley glaciers are found in high mountains where average temperatures keep the ice and snow from melting in the summer.

Valley Glaciers n As the ice moves it pushes loose materials out of its path. n Plucking is when boulders, gavel, and sand are added to the bottom of the glacial ice. n The glacier leaves behind distinctive features: arete, cirque, striations, moraines, U-shaped vallies. Fig 7-12

Glacial Deposition n Till- a mixture of different sized sediments dropped from a glacier. n Fig. 7-3 p. 184 shows various features of glacial deposition and outwash plain.

ARETE

MORAINE

Wind n Deflation, is the removal of finer particles by the wind. Sand, silt, and clay are blown away leaving larger size particles behind. n Abrasion, is the wearing of other rocks by the wind carried particles such as sand.

Sand and Dust Storms n Sand storms occur in the desert and at the beach. n Dust storms occur when very dry soil is blow away by the wind.

Reducing Wind Erosion n Windbreaks made of plants prevent reduces the wind energy. n Roots help hold soil together.

Loess n Fine-grained wind deposits.

Dunes n A mound of sand drifted by the wind. n Dunes are constantly moving, one sand grain at a time. n Fig. 7-21, p. 195, illustrates the migration of a dune.