Transcript Weathering and Erosion

Weathering and Erosion
Weathering
• The breakdown of the materials of Earth’s
crust into smaller pieces.
2 Types of Weathering
• Physical Weathering
• Chemical Weathering
Physical Weathering
• Process by which rocks are broken down
into smaller pieces by external natural
conditions.
• Types of Physical weathering
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Frost heaving and Frost wedging
Plant roots
Friction and impact
Burrowing of animals
Temperature changes
Wind
rain
-humans!
Frost Wedging
When water freezes in
cracks and expands,
causing the cracks to
increase in size.
Frost Heaving
Plant Roots
As plants grow, their
roots also grow. This
can cause rocks to
break from the force.
Friction and Repeated Impact
Water or wind can continuously
impact rocks, causing them to
breakdown. This is how streams
become rivers.
Burrowing of Animals
Some animals build homes in the ground.
These holes weaken the land.
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
Erosion
• The process by which water, ice, wind or
gravity moves fragments of rock and soil.
• Erosion (transport)
There are 5 main agents of
erosion:
1. *Running Water*
2. Glaciers
Weathering has to happen before erosion. The rocks
3. Wind
have to be broken into smaller sediments before they
4. Gravity
can be eroded away.
5. Man
Wind Erosion
Glacier
Water Erosion
• Rivers, streams, and runoff
Ice Erosion
• Glaciers
Wind Erosion
Gravity
Mount Rushmore
It will not be there forever!!
There is a pile of weathered material
at the bottom. It is slowly being eroded
down hill by gravity.
Man
• There are 5 ways that man can cause
erosion:
1. Forestry – all vegetation of removed, and without
roots, the soil will erode away.
2. Strip Mining – removing rock cover to get to the
resources below, which causes the loose sediments
to erode away.
3. Construction – the clearing of land to build
buildings/houses also causes all loose soil to erode
away.
4. Improper Farming – not plowing the land at right
angles to slopes causes soil to erode away.
5. Salting Highways – the salt is washed off the road
to the sides, where it prevents vegetative growth
along the sides.
Mass Wasting
• Landslides, mudslides, slump and creep
landslide clip.mpeg
Landslide- Downslope movement of rock, soil, and mud.
Mudslide- rapid downslope movement of a mixture of water,
rock, and soil
Slump- A type of landslide in which a mass of rock breaks
away along a curved surface and rotates more or less intact
downslope.
Creep- a slow moving landslide
Deposition – the process where sediments are
released/dropped by their agent of erosion.
Most deposition happens in standing/still bodies of water
(oceans/lakes).
Deposition is caused by the slowing down (loss of kinetic
energy) of the agent of erosion.