Transcript Agents of Erosion - Bethpage Union Free School District

Agents of Erosion
AIM: What forces cause erosion?
Vocabulary
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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. Avalancheinvolves snow and ice
http://player.discoveryeducation.com/index.cfm?guidAssetId=B2F
A4835-7736-4E1E-BAAF841B64AF37F9&blnFromSearch=1&productcode=US
2. Wind
a. Erodes fine, small, loose, dry material
b. Contributes to abrasion (physical
weathering)
c. Affected by velocity, sediment size,
ground cover, water
d. 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 30s
Wind 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/Scie
nce600/co/530.php?iRef=530&iChapter=
16
 http://www.glencoe.com/sites/common_a
ssets/science/virtual_labs/E06/E06.html
 http://www.kineticcity.com/mindgames/w
arper
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:
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Valley glacier – long and narrow, forms high in
the mountains
Continental glacier – ice caps, covers much
land, ex – Greenland, Antarctica, Alaska
3. Glaciers
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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/eg
eo/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 Outwashsediments 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_a
ssets/science/virtual_labs/ES07/ES07.ht
ml
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.