Download Weathering and Erosion

Weathering, Erosion and
Deposition
Weathering
The breakdown do the materials of Earth’s
crust into smaller pieces.
Physical Weathering
• Process by which rocks are broken down
into smaller pieces by external conditions.
• Types of Physical weathering
– Frost heaving and Frost wedging
– Plant roots
– Friction and impact
– Burrowing of animals
– Temperature changes
Frost Wedging
Frost Heaving
Plant Roots
Friction and Repeated Impact
Burrowing of Animals
Temperature Changes
Chemical Weathering
• The process that breaks down rock
through chemical changes.
• The agents of chemical weathering
– Water
– Oxygen
– Carbon dioxide
– Living organisms
– Acid rain
Water
• Water weathers rock by dissolving it
Oxygen
• Iron combines with
oxygen in the
presence of water in
a processes called
oxidation
• The product of
oxidation is rust
Carbon Dioxide
• CO2 dissolves in rain water and creates
carbonic acid
• Carbonic acid easily weathers limestone
and marble
Living Organisms
• Lichens that grow on rocks produce weak
acids that chemically weather rock
Acid Rain
• Compounds from burning coal, oil and gas
react chemically with water forming acids.
• Acid rain causes very rapid chemical
weathering
Karst Topography
• A type of landscape in rainy regions where
there is limestone near the surface,
characterized by caves, sinkholes, and
disappearing streams.
• Created by chemical weathering of
limestone
Features of Karst: Sinkholes
Features of Karst: Caves
Features of Karst: Disappearing
Streams
What Caused This?
http://commons.wikimedia.org/wiki/File:Water_erosion_
below_Hay_Bluff_-_geograph.org.uk_-_1074175.jpg
http://commons.wikimedia.org/wiki/File:Wind_erosion_
Seminole_Canyon.JPG
THAT’S RIGHT! EROSION!
http://commons.wikimedia.org/wiki/File:Bave
ntian_Clay_Beds_-_geograph.org.uk__1776748.jpg
Erosion
• The process by which water, ice, wind or
gravity moves fragments of rock and soil.
Water Erosion
• Rivers, streams, and runoff
Ice Erosion
• Glaciers
Wind Erosion
Mass Movements
• Landslides, mudslides, slump and creep
landslide clip.mpeg
What is Deposition?
• Laying down of sediment that has been
transported by a medium such as wind, water, or
ice
– Process of erosion stops:
• when the moving particles fall out of the transporting
medium and settle on a surface
– Speed of the medium slows or the resistance of the
particles increases, the balance changes and causes
deposition
– Speed can be reduced by large rocks, hills, vegetation, etc.
Deposition - Wind
Wind speed can be related to variations in
heating and cooling.
 Transportation of particles in wind:
– Fine particles in suspension hundreds of km from its original
source in the desert
– Heavier material may be blown along the ground.
– Material is deposited when the wind changes direction or loses its
strength.
http://commons.wikimedia.org/wiki/File:Desert_Chihuahuan_Big_Bend.JPG
Deposition - Water
• Running water enters a large, fairly still body of
water and its speed decreases.
• SPEED
• As the speed of the water decreases, the water's ability to carry
sediment also decreases.
• Deposited in streams, rivers, and oceans:
• Running water deposits sediments where the slowing water can
no longer move them.
• Largest particles are deposited near the shore.
• Increasingly smaller particles settle out farther from the shore
where the water is calmer.
http://commons.wikimedia.org/wiki/File:Enchanted_Rock,_stream.jpg
Delta – a fan shaped deposit that forms at the mouth of a river/stream when
it enters a larger body of water like an ocean or lake
Alluvial Fan - a fan shaped deposit of sediments that forms when a
stream/river flows out of a mountain on to flat, dry plains. These are not under
water and are very visible. This only happens on the land. You can call it a
“land delta”.
Deposition - Ice
• Glacial flows of ice
– become slower when the ice begins
melting
– Deposits left by glaciers:
– The deposits of these rivers look similar to normal river deposits and are
called outwashes.
– Moraines are large chunks of broken rock left at the base and sides of
the glacier as it melts and recedes.
– Finer material is carried in the rivers that form when the glacial ice
melts.
http://commons.wikimedia.org/wiki/File:Cavell_Glacier_with_Crevices_and_Annual_Rings.jpg
What’s the Difference?
• WEATHERING – Think of weather wearing rock down.
• EROSION – Think of a road and traveling.
• DEPOSITION – Think of depositing money into a
bank.