Transcript Weathering and Erosion - Mr. Ahearn's Earth Science

Weathering, Erosion,
Deposition
Mr. Ahearn
Earth Science 2010
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
Describe how ice causes
weathering?
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
What evidence of
weathering do you see in
this picture?
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
Rates of Weathering will depend on:
• Climatic Conditions:
– Cold and/or dry climates favor
physical weathering.
– Warm and wet climates favor
chemical weathering.
– Frost action works best in areas
where the temperature fluctuates
wildly.
Where is the rock more resistant to
weathering?
Where is the rock least resistant to
weathering?
Complete Questions #1-16
Review Book p. 82
Erosion
• The process by which water, ice, wind or
gravity moves fragments of rock and soil.
What is Erosion?
• Erosion, is gradually wearing down
the surface of the earth.
• Erosion is the process by which
weathered rock and soil (sediment) are
moved from one place to another.
• Erosion carves the Earth's surface
creating canyons, gorges, and even
beaches.
Erosion
How much erosion takes place is
determined by the:
• Sum
• Slope
• Speed
• Surface
Water Erosion
• Rivers, streams, and runoff
Water Erosion
When rain falls to the Earth it can evaporate,
sink into the ground, or flow over the land
as Runoff.
When it flows over land, erosion occurs.
Runoff picks up pieces of rock and "runs"
downhill cutting tiny grooves (called rills)
into the land.
Ice Erosion
• Glaciers
Glaciers
Glaciers can pick up and carry sediment that ranges in
size from sand grains to boulders bigger than houses.
Moving like a conveyor belt and a bulldozer, a single
glacier can move millions of tons of material!
Wind Erosion
Mass Movements
• Landslides, mudslides, slump and creep
Slower
Faster
landslide clip.mpeg
Plants Can Prevent Erosion
Complete Questions 24-37
Review Book p. 88
Deposition
Rock particles that are picked up and transported
during erosion will ultimately be deposited
somewhere else
Deposition is the process by which sediments (small
particles of rock) are laid down in new locations.
• Together, Erosion and Deposition build new
landforms.
• Deltas
• Canyons
• Meanders
• Floodplains
Delta
• Where rivers meet the
ocean is called the
mouth of the river.
Soil and dirt carried
by these rivers is
deposited at the
mouth, and new land
is formed. The new,
soil-rich land is known
as a Delta
Canyons
Canyons are large valleys
created by a river or stream.
Meander
Meandering streams wander side to side as they constantly
seek out the lowest elevation.
This constant motion creates a series of S-shaped “loops”.
Floodplains
• These are low-lying
areas along the sides of
a river channel that have
regular times of heavy
waterflow to cause the
river to spill over and
flood the land.
Complete Questions 38-56
Review Book p. 91
The End