Erosion

and

Deposition

Agents, Forces, and Results

What Caused This?

What is Erosion?

•Erosion – moving of rock material from one place to a new location

Weathering has to happen before erosion. The

rocks have to be broken into smaller sediments

before they can be eroded away.

Weathering & Erosion Study Jams

AGENTS OF EROSION

•Wind

•Flowing water

•Waves

•Gravity

•Moving Ice (glaciers)

What Is Wind Erosion?

• Wind – sediments that have been transported by wind appear pitted (holes) and frosted (glazed) – Effective in moving small, loose material

– Occurs in areas where there is not enough rainfall to support vegetation

– Main effects: 1. Wind causes small particles to be lifted and moved away.

2. Suspended particles may impact on solid objects causing erosion by abrasion (rubbing).

What Is Water Erosion?

• Flowing Water – sediments transported by water appear rounded and smooth

– Most influential force in erosion

– Transports large objects with fast moving streams

– Helps create landforms:

• rivers

• lakes

• oceans

What Is Wave Erosion?

• Waves – relentless pounding can throw broken rocks against the shore and wash away fine grains

• Erodes (transports):

• softer/weaker rock first

• harder/more resistant left behind

• Can create landforms based on where waves hit land and which rocks they transport

What Is Gravitational Erosion?

• Gravitational Erosion – 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

What Is Glacial Erosion?

• Glaciers– moving ice that carries rocks; appear

scratched and grooved

What is Deposition?

• Deposition – the process where sediments are released/dropped by their agent of erosion

– 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

Transportation of particles in wind:.

– Material is deposited when the wind changes direction or loses its

strength.

– Fine particles can be deposited hundreds of km from its original

source in the desert

– Heavier material may be blown along the ground

–Dunes: a mound that forms when particles suspended in the

wind hit an obstacle and stop

Deposition - Water

• 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.

DEPOSITION - ICE

• Glacial flows of ice – become slower when the ice begins melting

– Deposits left by glaciers:– look similar to normal river deposits and are called outwashes.

– Moraines are large chunks of broken rock left at the base and sides of the glacier as it melts and recedes.

– Finer material is carried in the rivers that form when the glacial ice melts.

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.