Erosion and deposition

Erosion and deposition

1. Erosion and Deposition Agents, Forces, and Results Presented by Md. Nazir Hossain Lecturer Geography and Environment Shahjalal University of Science & Technology Sylhet-3114, Bangladesh [email protected] GEE-421: Geomorphology-II Chapter 1

2. What Caused This? 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 http://commons.wikimedia.org/wiki/File:Water_erosion_below_Hay_Bluff_-_geograph.org.uk_-_1074175.jpg

3. 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 g ravity wind

4. Water – most influential force in erosion Moves materials Transports large objects with fast moving streams Wears away rocks: rivers lakes oceans What Is Water Erosion ? Erosion caused by flooding

5. Wind – responsible for wearing away rocks and creating great deserts like the Sahara Desert and Gobi Most effective in moving loose material M ain 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 What Is Wind Erosion ? Extreme erosion caused by wind over long periods of time

6. 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 of the coastline. What is Wave Erosion ?

7. 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 s moothing p olishing the rock surface What Is Glacial Erosion ?

8. Mass movement – downward movement of rock and sediments, mainly due 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 What is Gravitational Erosion ?

9. 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.

10. Running water enters a large, fairly still body of water and its speed decreases. SPEED A s 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. Deposition - Water

11. 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. Deposition - Wind

12. Glacial flows of ice – become slower when the ice begins melting – Deposits left by glaciers: The deposits of these rivers look similar to normal river deposits and are called outwashes . Moraines are large mass of broken rock left at the base and sides of the glacier. Finer material is carried in the rivers that form when the glacial ice melts. Deposition - Ice

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

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