agents of erosion aim: what forces cause erosion?
TRANSCRIPT
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
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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.
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.