Agents of Erosion

AIM: What forces cause erosion?

Vocabulary

Erosion Mass movement Landslide Creep Slump Mudslide Avalanche Liquefaction

Retaining Walls Slope

1. Erosion

Movement of sediments from one location to another.

Landforms are created by a combination of weathering and erosion.

Often the forces that cause erosion also cause the weathering of the sediment at the same time.

2. Gravity

a.    ***Driving force of all erosion **** b.    Causes Mass Movement or Mass

Wasting (Ex - Landslides, mudslides, slump and

creep) c.    Affected by slope, ground cover, water,

climate Can be triggered by earthquakes d. Sediments are angular and rough

a. Landslides or rockslides – fast moving

Retaining walls and metal nets help prevent landslides

b. Mudslides Downward flow of water,

rock and soil After heavy rain when

ground is overly saturated, where vegetation has been stripped, and on steep slopes

Volcanoes can trigger a melt Liquefaction – when the

land becomes fluid and moves

c. Slump – a sudden sag or dip

d. Creep – very slow movement downhill

Slanted fences, walls, trees or gravestones are a sign of creep.

e. Avalanche- involves snow and ice

http://player.discoveryeducation.com/index.cfm?guidAssetId=B2FA4835-7736-4E1E-BAAF-841B64AF37F9&blnFromSearch=1&productcode=US

2. Wind

a. Erodes fine, small, loose, dry materialb. Contributes to abrasion (physical

weathering)c. Affected by velocity, sediment size,

ground cover, waterd. Sediments are angular with frosted or

pitted appearance e. Occurs in deserts, arid areas, seashores

Wind erosion forms sand dunes.

http://www.physicalgeography.net/fundamentals/10ah.html

Wind makes odd shapes and angular rocks

Wind also makes swirly patterns

The Great Dust Bowl – the Dirty 30sWind can erode away topsoil

Vegetation reduces erosion of dunes

Draw a sand dune with the sand blowing from the right.

How does gravity play a role in wind erosion?

Gravity causes wind to drop it’s sediments in a new location.

What kind of weathering does wind cause while it’s eroding sediments?

Wind carries sand and fine particles which can abrade rock (abrasion by wind).

Weatherhing and erosion games

http://www.glencoe.com/sec/science/Science600/co/530.php?iRef=530&iChapter=16

http://www.glencoe.com/sites/common_assets/science/virtual_labs/E06/E06.html

http://www.kineticcity.com/mindgames/warper

1) The photograph shows a sand dune that formed in a coastal area.                                                 This sand dune was most likely formed by

A) water flowing from the left

B) water flowing from the right

C) wind blowing from the left

D) wind blowing from the right

The picture below shows a geological feature in the Kalahari Desert of southwestern Africa.                                                                       Which process most likely produced the present appearance of this feature? A) wind erosion

B) volcanic eruption

C) earthquake vibrations

D) plate tectonics

3. Glacial Landmasses

a. Glacier – a large mass of moving ice, found in areas of

- High elevation ( mountaintops)- High latitude ( polar regions)

b. Two types: Valley glacier – long and narrow, forms high in

the mountains Continental glacier – ice caps, covers much

land, ex – Greenland, Antarctica, Alaska

3. Glaciers c. Gravity pulls weight of glacier down mountain d. Glaciers can move cm/day e. Affected by slope, weight, and velocity f. Erodes many sizes - boulders to sand g. Sediments are unsorted (mixed sizes) h. Sediments have sharp angles, irregular

shapes,rough, grooves (striations) i. Carve U-shaped valleys

Ice ages – when glaciers covered large parts of the Earth’s surface

Glaciers – carve a U-shaped valley

As the glacier moves it drags sediment downhill.

Other glacial landforms

Glacial erosion

Plucking – rocks freeze to the glacier and moves it

Abrasion – rocks in glacier scratch bedrock causing striations

Striations – grooves carved in rock can tell you the way a glacier moved

Glacial Deposition

When sediments are eroded, they must come to rest somewhere. They are deposited in a location that creates a landform.

Glaciers deposit sediments, as well as water, wind and gravity.

Glacial Deposition Till – the sediment piles

that are created by glaciers are unsorted deposits, meaning they have many shapes and sizes of sediments.

Glacial Deposition

Moraine – till deposited at the edge of a glacier makes a mound

How moraines are formed

http://www.wwnorton.com/college/geo/egeo/flash/18_1.swf

Glacial Deposition

Drumlin-elongated whale-shaped hill formed by glacial ice. They point the direction of glacial retreat.

Glacial Deposition

Glacial Erratic – a boulder dragged by a glacier to a new location, from a different origin

Glacial Deposition

A kettle lake is a hole left by a chunk of ice and filled by melting glacial water and runoff.

Glacial Deposition

Glacial Outwash- sediments washed away from the glaciers front end. These sediment are deposited, sorted by size in layers.

Glacial Deposition

Eskers – a long winding ridge formed when a river of melting ice forms inside the glacier

Glacial Outwash

Glacier Game

http://www.glencoe.com/sites/common_assets/science/virtual_labs/ES07/ES07.html

4. Wave Action

a. Wave action brings in (deposits) and carries away (erodes) sand along coastlines.

b. Wind creates waves.

b. Affected by tides.

c. Sediments are rounded from abrasion.

Waves shaping the coast

5. Stream erosion (Running Water)

a.    ****Primary agent of erosion ****

b.    Size of sediment carried depends on velocity of water

c.    Sediments are rounded from abrasion

d. Carve V-shaped valleys

Stream carved V-shaped valley

Streams weather and erode waterfalls – softer rock erodes, while harder rock remains

Waterfall formation waterfall formation

Broken boulders at the bottom of the falls

Question…

Which agents of erosion also weather rocks at the same time?

Question…

How is gravity involved in stream erosion?

Now it’s your turn…

1. Look at the following pictures

2. Identify the type of erosion

3. Match the cut-out sediment type transported in each example.