Erosion, Deposition, and Mass Movement Chapter 12

What is Erosion? Erosion is the transport of sediments…weathering breaks the rocks down and erosion carries them away for deposition Can be caused by wind, water, or ice Wind transports sediments by saltation, picking up grain by grain Deserts are a great location to see erosion and deposition going on in the form of dunes Great Sand Dunes National Monument. Mosca, Colorado Sand dune in the Sahara Desert, Lybia

Erosion by Ice As glaciers move across the Earth’s surface, they erode, move, and deposit large amounts of sediment Two kinds of glaciers are alpine (valley) and continental (also called ice sheets) As glaciers move, huge cracks can form, called crevasses A glacial crevasse Glacial Bay in Alaska

Glacial Landforms Horn – Mt. Simpson Glacier National Park in Montana U-shaped valley in the Alps Cirque in Colorado Arete in Wind-River Range in Wyoming

Glacier Deposits When glacial ice melts, it leaves behind a depression called a kettle (which gets filled in with the glacial melt and called a kettle lake) Sediments left behind when ice melts is called till, and the most common kind is a moraine 4 kinds of moraines 1. 1.Lateral: forms along each side of glacier 2. 2.Medial: when two lateral moraines of two glaciers meet 3. 3.Ground: unsorted sediment below a glacier 4. 4.Terminal: found at the leading edge of a glacier Medial moraine Lateral

Gravity and Mass Movement A rock fall in Big Bend National Park, Texas Slump of soil down slope along a curved surface Both pictures showing the evidence of creep, the very slow movement of the top layers of soil. Many times this can lead to curved tree trunks and tilted fences.