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AGENTS OF EROSION

WHAT IS EROSION?

• Erosion is the process of weathered rocks and soil moving from one place to another

• Erosion moves sediments- tiny pieces of broken rock or soil

• After erosion, deposition occurs when the pieces of sediments and soil settle on land or in water.

AGENTS OF EROSION

There are 5 agents (or causes) of erosion: 1. Gravity2. Moving Water3. Glaciers4. Waves5. Wind

(1) GRAVITY

• Definition: the force that pulls all things towards the earth’s center• Erosion begins with gravity pulling material

towards the center of the earth• Mass Movement is the downhill movement of

weathered materials caused by gravity

WHAT DOES GRAVITY CREATE?

• Mass movement, caused by gravity, can create:

1. Mudflows- water, rock, and soil mixed together that moves downhill

2. Landslides- when rock and soil slide quickly down a steep slope

3. Slumps- a mass of rock and soil suddenly slips down a slope in one large piece

4. Creep- slow downhill movement of rock and soil

(2) MOVING WATER

• Why it matters: Moving water has shaped more of the earth’s surface than any other agent• Moving water creates runoff- water from rain or

snow that flows into streams and rivers• More runoff means more erosion!

• Moving water can form the following: 1. Streams2. Valleys3. Waterfalls4. Deltas…. And more!

WATER EROSION

• Through erosion, a river can create valleys, waterfalls, flood plains, meanders, and oxbow lakes.

1. Waterfalls- formed when a river meets hard rock that erodes slowly

2. Flood Plain- flat, wide area of land along a river formed from water over gently sloping land

WATER EROSION

3. Meanders- a loop-like bend in a river that is formed from water flowing through soft rock

4. Oxbow Lakes- a meander that has been cut off from the river due to sediments from a flood

WATER DEPOSITION• Every time water moves, it carries sediments with it

that are dropped off in new places• Through deposition, moving water can create

landforms, such as deltas and alluvial fans1. Deltas- a triangular deposit of sediment located

at the mouth (end) of a river that empties into a still body of water (like an ocean or lake)

2. Alluvial Fan- a wide, sloping deposit of sediment formed where a stream leaves a mountain range

VIDEOS

Summary of water erosionhttp://www.schooltube.com/video/e920ff2f44ed84d96788/HowStuffWorks-Show-Episode-4-Power-Of-Water-Erosion

What is the role of plate tectonics in water erosion? https://www.youtube.com/watch?v=f62_MjB6-Ok

GROUNDWATER EROSION

• Sometimes rain or snow melts and is soaked into the ground, filling in cracks in rocks, creating groundwater erosion• Groundwater can cause

erosion through chemical weathering. • Water combines with carbon

dioxide to create carbonic acid. Carbonic acid can wear down certain rocks and create caves.

AGENTS OF EROSION

There are 5 agents (or causes) of erosion: 1. Gravity2. Moving Water3. Glaciers4. Waves5. Wind

We are going to focuson the last 3 today!

(3) GLACIAL EROSION

• Definition: a glacier is a large mass of ice that move slowly over land • 2 types of glaciers1. Continental: glacier that covers

most of a continent or large island and they flow in all directions

2. Valley: a long, narrow glacier that forms when snow and ice build up high in a mountain valley

ICE AGE

• An ice age is when a continental glacier covers a large part of the earth’s surface• About 1 million years ago, 1/3 of earth’s land was

covered in glaciers!

What is the ice age?https://www.youtube.com/watch?v=dJ5GYQrkvxI Movie Preview: 1. What types of erosion do you see? 2. What about this preview is realistic? Unrealistic?https://www.youtube.com/watch?v=cMfeWyVBidk

HOW GLACIERS CAUSE EROSION

2 processes by which glaciers erode the land1. Plucking: when rocks are broken by moving

glaciers and then freeze to the bottom of the glacier. As the glacier moves, the frozen rocks stuck to the bottom move, too.

2. Abrasion: when these frozen rocks stay on the glacier and are dragged across the land. This dragging of rock can scratch the rock.

HOW GLACIERS CAUSE DEPOSITION

Once a glacier melts, it deposits the sediment it eroded from the land, creating various landforms. These sediments deposited by a glacier are called till

Glaciers can create the following landforms: • Moraine- when a glacier deposits a mountain or

ridge• Kettle- a small depression or ice is left in a glacial

till • Fiord- a valley that was created by a glacier that is

now filled with water• Cirque- a bowl-shaped hollow eroded by a glacier

(4) WAVE EROSION

How do waves cause erosion and deposition? • Energy in waves come from the wind• When the wind hits the water, waves form• As the wave hits the shore, it moves the sand

forward, then backwards into the water. • The waves also shape the shoreline

https://www.youtube.com/watch?v=775FQ5_YLvE

WAVE EROSION

Waves shape the coast through erosion by breaking down rock and moving sand and other sediment

Waves change direction based on the land masses that they hit

A headland is a part of the shore that sticks out into the ocean

WHAT WAVES CAN CREATE

Wave erosion can create…• Sea Cave• Wave-Cut Cliff• Sea Arch

Wave deposition can create…• Beaches• Sandbars• Barrier Beaches• Splits

(5) WIND EROSION Wind causes erosion by deflation. • Deflation: the process by which wind

removes surface materials, like sediments and sand, to new place

Wind deposition occurs once the sediments picked up by wind fall to the ground. This can create…• Sand dunes- wind blown sediments

that has built up • Loess deposits- pieces of sediment

smaller than sand that are carried by the wind