Download FACTORS AFFECTING WEATHERING RATES

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TOPIC 9
WEATHERING & EROSION
Weathering
Vs.
 The breakdown of
rock material
Erosion
 The transport of
broken down rock
material
Weathering
Physical
 Breakdown of rock
material without
changing the
chemical makeup of
the rock.
Example: smashing
chalk with hammer.
Chemical
 Breakdown of rock
material by changing
the chemical makeup
of the rock
Example: dissolving
chalk in acid
 Frost Action- water
expands when frozen
 Plant Action
 Abrasion
 Oxidation
 Carbonation
 Hydration
Cape May “Diamonds”
FACTORS AFFECTING
WEATHERING RATES
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Particle Size
Composition of Rock
Climate
Exposure
Particle size:
rate
 As particle size increases, weathering
rate decreases. (indirect relationship)
 This is due to an increase in surface
area.
size
Composition:
 Some rocks are more resistant to
weathering than other rocks.
 Rocks that are more resistant will weather
slower than those that are less resistant.
More resistant
Less resistant
You might also see it like this…
Climate:
 Warm climates - Chemical weathering
 Cold climates - Physical weathering
 As moisture increases, weathering rates
increase or…
 “Wetter is Better !!!”
 a warm, moist climate will have greater
weathering rates than a warm, dry
climate
Cleopatra’s Needle
Exposure:
 As a rocks exposure to the Earth’s surface
increases, the weathering rate increases.
Im OK!
EROSION:
*GRAVITY is the driving
force behind erosion !
The 5 Agents of erosion are…
Streams
Glaciers
Wind
Waves
Gravity
Stream Erosion
 The most predominant agent of erosion.
 Why?
 Methods of transport:
Stream velocity depends
on…
 Gradient (slope)
-as slope increases, velocity increases.
 Discharge (amt. of water in the stream)
-as discharge increases, velocity
increases.
Velocity vs. Sediment
 When the velocity increases…
1. The amt. of sediments carried
increases
2. The size of the sediments carried
increases.
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Erosion
Frost action
Oxidation
Caves
Abrasion
Plant action
Hydration
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Weathering
Discharge
Meander
Delta
Alluvial fan
Horizontal sorting
Streams move fastest…
 Just below the
surface
 In the center of the
channel
Meanders
High KE
More Erosion
Low KE
Less Erosion
* Water moves
fastest on the
outside of
meanders.
DELTA:
 Sediments deposited at the mouth of a
stream.
 Sediments are deposited because the
stream velocity decreases abruptly.
Horizontal Sorting
 The sediment size decreases as the
distance from the mouth increases.
Largest Sediments
Smallest sediments
Alluvial Fan (land delta)
 Fan shaped deposit formed when
streams flow off of mountains onto more
level land.
Stages of Stream
Development
Stream Sediments
 Sediments deposited by a
stream are usually sorted,
rounded and smooth.
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Narrow V-shaped
Downcutting
Swift water
Steep gradient
Erosion is dominant
 Wide meanders and oxbow
lakes
 Wide floodplain
 Low velocity
 Low gradient
 Dynamic equilibrium between
erosion and deposition
Glaciers
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Large mass of
moving ice.
Continental vs.
Mountain glaciers.
Ice forms from the
pressure caused by
the weight of the
accumulating
snow.
Glacial features:
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Till- sediments transported by
glaciers
Sediments are Unsorted and
Angular.
Glacial features:
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Till- sediments transported by
glaciers
Sediments are Unsorted and
Angular.
Striations- scratches and grooves in
bedrock.
Glacial features:
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Till- sediments transported by
glaciers
Sediments are Unsorted and
Angular.
Striations- scratches and grooves in
bedrock.
Erratics-large boulders deposited by
a glacier that DO NOT match the
local bedrock.
U- Shaped Valleys

Stream Valley

Glacial Valley
Moraines
Other Features:

Drumlins
Other Features:
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Drumlins
Eskers
Long Island- Terminal Moraine
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Long Island- Terminal Moraine
Finger Lakes
Other Features:
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Drumlins
Eskers
Kames
Long Island
Finger Lakes
Crevasses
Valley Glacier
Continental Glacier
Till
Erratics
Striations
Drumlins
Eskers
Kettles
Kames
Outwash Planes
Outwash
Moraine
WIND EROSION

Wind transported sediments are…
1. Small
2. Dry
3. Loose (free to move)
** Sediments are frosted and pitted
Features:

Wind erosion may cause abrasion.
ex: Arches, toadstools, ventifacts, desert
pavement
Deflation
Sandblasting

Winds blow sand against rocks causing
abrasion.
Dune:

Deposit of windblown sand.
WAVE EROSION
 Sediments are transported due to the
energy created by breaking waves.
Mass Movement:
 Any variety of erosion and/or deposition
done directly by gravity.
Examples:
 Rock slides
 Avalanches
 Slump
 Creep
Deposits are unsorted and angular.
 Mr. Arcuri
 John Deere
 Cafeteria
 Mr. Egresits
 Stewarts
 Golden Knights
 Mr. Andrews
 Mr. Goodelle