Agents, Forces, and Results Erosion Agents, Forces, and Results

What Causes This? http://commons.wikimedia.org/wiki/File:Water_erosion_below_Hay_Bluff_-_geograph.org.uk_-_1074175.jpg http://commons.wikimedia.org/wiki/File:Wind_erosion_Seminole_Canyon.JPG http://commons.wikimedia.org/wiki/File:Baventian_Clay_Beds_-_geograph.org.uk_-_1776748.jpg

What Is Erosion? Erosion – moving of rock material from one place to a new location Three processes must take place: detachment of particles lifting them transporting them Agents of erosion: water moving ice gravity wind Sand consists of small pieces of rock that have been: weathered from a parent rock eroded deposited somewhere else

What Is Wind Erosion Wind – responsible for wearing away rocks and creating great deserts like the Sahara Desert and Gobi Most effective in moving loose material Main effects: Wind causes small particles to be lifted and moved away. Suspended particles may impact on solid objects causing erosion by abrasion (rubbing). Occurs in areas where there is not enough rainfall to support vegetation http://commons.wikimedia.org/wiki/File:Wind_Erosion_Features_in_Wadi_Al-Hitan.jpg

Wind Erosion Wind will carry fine, dry sediments over long distances.

Wind Transport of Dust Photo shows Sahara Desert sand being transported over the Atlantic Ocean.

What Is Water Erosion Water – most influential force in erosion Moves materials Transports large objects with fast moving streams Wears away rocks: streams (rills, gullies, creeks, rivers, etc.) lakes oceans

Stream Erosion Flowing water will lift and carry small sediments such as silt and sand.

Stream Erosion and Deposition Where water moves more swiftly there will be more erosion. Where the water slows down, sediments will be deposited.

Wave Erosion Waves – relentless pounding Erodes: softer/weaker rock first harder/more resistant left behind Can take over 100 years to erode a rock to sand Energy of waves and chemical content of the water erodes the rock off the coastline. http://commons.wikimedia.org/wiki/File:Wave_Erosion,_Downpatrick_Head_-_geograph.org.uk_-_369272.jpg

Ocean Dynamics Tidal action and waves carry away weathered materials.

What Is Gravity Erosion? When sediments are weathered they may be transported downward by gravity. Mass wasting – downward movement of rock and sediments, mainly due to the force of gravity

Gravitational Erosion When sediments are weathered they may be transported downward by gravity as a slump. Slump

Gravitational Erosion Loose sediments transported by gravity are called creep. Creep Field

What Is Glacial Erosion? Ice – moves and carries rocks, grinding the rocks beneath the glacier Most powerful agent of erosion because of size, weight, and density Plucking occurs when water enters cracks under the glacier. freezing breaking off pieces of rock that are then carried by the glacier Abrade (abrasion) Scratches and cuts grooves into the rock under the glacier Smoothes and polishes the rock surface Forms U-shaped valleys http://commons.wikimedia.org/wiki/File:U-shaped_valley_at_the_head_of_Leh_valley,_Ladakh_(2).JPG

Glaciers Form at Earth’s poles and in high elevations (mountainous areas) Valley Glaciers Form in valleys of mountainous areas Occurs when ice is too heavy, flows down the mountain like liquid Continental Glaciers Cover a continent-sized area Thickest at center Callled Ice Sheets

Glacial Erosion