Erosion and Deposition Agents Forces and Results ule

Erosion and Deposition Agents, Forces, and Results ule R. A Dept. of Geography

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: • flowing water • moving ice • waves • gravity • wind – Sand is composed of small pieces of rock that have been: • weathered from a parent rock • eroded • deposited somewhere else

What Is Wind Erosion ? • Wind – wears away rocks and is responsible for the creation of deserts such as the Sahara and the Gobi - Most effective in moving loose material – Main effects: 1. Wind lifts small particles and moves them away. 2. Suspended particles may cause erosion on solid objects by abrasion (rubbing). – Occurs in areas where there is not enough rainfall to support vegetation http: //commons. wikimedia. org/wiki/File: Wind_Erosion_Featu res_in_Wadi_Al-Hitan. jpg

What Is Water Erosion ? • Water – most influential force in erosion – Moves materials – Transports large objects with fast moving streams – Wears away rocks: • rivers • lakes • oceans http: //commons. wikimedia. org/wiki/File: Water_er osion_below_Scarsoch_Bheag__geograph. org. uk_-_1367808. jpg

What Is 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 chemicals contained in the water erode the rock off the coastline. http: //commons. wikimedia. org/wiki/File: Wave_Erosion, _Downpatri ck_Head_-_geograph. org. uk_-_369272. jpg

What Is Gravitational Erosion ? • Mass Movement – downward movement of rock and sediments, due primarily to the force of gravity – Streams and glaciers • move material from higher to lower elevation – Occurs continuously on all slopes » slow moving and sudden movement until equilibrium is reached http: //commons. wikimedia. org/wiki/File: Purbeck_, _Old_Har ry_-_geograph. org. uk_-_1711962. jpg

What Is Glacial Erosion ? • Ice – moves and carries rocks, grinding the rocks beneath the glacier – Plucking occurs when water enters cracks under the glacier. • freezing • breaking off pieces of rock that are then carried by the glacier – Abrade (abrasion) • cuts into the rock under the glacier • smoothing • polishing the rock surface http: //commons. wikimedia. org/wiki/File: Ushaped_valley_at_the_head_of_Leh_valley, _Ladakh_(2). JPG

What is Deposition ? • Deposition – laying down of sediment that has been transported by a medium such as wind, water, or ice – Process of erosion stops: • when the moving particles fall out of the transporting medium and settle on a surface – Speed of the medium slows or the resistance of the particles increases, the balance changes and causes deposition – Speed can be reduced by large rocks, hills, vegetation, etc.

Deposition - Wind § Wind speed can be related to variations in heating and cooling. § Transportation of particles in wind: – Fine particles in suspension hundreds of km from its original source in the desert – Heavier material may be blown along the ground. – Material is deposited when the wind changes direction or loses its strength. http: //commons. wikimedia. org/wiki/File: Desert_Chihuahuan_Big_Bend. JPG

Deposition - Water • Running water enters a large, fairly still body of water and its speed decreases • SPEED • As the speed of the water decreases, the water's ability to carry sediment also decreases. • Deposited in streams, rivers, and oceans: • Running water deposits sediments where the slowing water can no longer move them. • Largest particles are deposited near the shore. • Increasingly smaller particles settle out farther from the shore where the water is calmer. http: //commons. wikimedia. org/wiki/File: Enchanted_Rock, _stream. jpg

Deposition - Ice • Glacial flows of ice – become slower when the ice begins melting – Deposits left by glaciers: – Outwashes are deposits similar to those left by rivers. – Large chunks of broken rock deposited at the base and sides of the glacier as it melts and recedes are called Moraines. – When the glacial ice melts, smaller material is carried by the rivers. http: //commons. wikimedia. org/wiki/File: Cavell_Glacier_with_Crevices_and_Annual_Rings. jpg

What’s the Difference? • WEATHERING – Think of weather wearing rock down. • EROSION – Think of a road and traveling. • DEPOSITION – Think of depositing money into a bank.