WeatheringWeathering
And And
ErosionErosion
Weathering
And
Erosion
WeatheringThe breaking down of the Earth’s crust into smaller
pieces. It is caused by physical, chemical, or biological means.
The Different Types of Weathering
Physical WeatheringProcess 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
Frost Action or ice wedging slowly breaks up this sedimentary rock into
unusual shapes.
Root Pry
The tree is growing in the rock and soon the rock will break apart
because of the tree roots.
Plant Roots
Friction and Repeated Impact
Burrowing of Animals
Temperature • Temperature can produce mechanical
weathering. During the day, the sun’s energy heats a rock’s surface. During the night, the rock’s surface cools. The repeated change from hot to cold may cause the rock to peel or flake layers that are parallel to the rock’s surface. This peeling or flaking is known as exfoliation.
Temperature Changes
This is a picture of the
Half Dome. The rock is
peeling away from the
mountain in layers just
like an onion. This is
exfoliation.
These rocks have been blasted by wind and sand causing them to become rounded.
WIND ABRASION
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
This rock is red because of the oxidation of iron in the
sediment when the rock was being formed.
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
Acid Rain
1908 to 1969
Acid rain has eaten away this limestone statue.
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: Caves
Features of Karst: Disappearing Streams
Features of Karst: Sinkholes
Erosion• The process by which water, ice, wind or gravity
moves fragments of rock and soil.
• Erosion loosens & transports sediment formed by weathering.
ErosionThere are many kinds of
Erosion.
Here are a few:• Wave Action
• Running Water
• Landslides
• Avalanche
•Glaciers
• Slump
•Creep
• Rock Fall
• Mud Flow
Erosion
Moving water & wind cause changes to existing land forms & create new landforms such as valleys, plateaus, flood plains, canyons, caves or dunes
Colorado River as it winds its way through the Grand Canyon.
Grand Falls, near Leup, Arizona
Water Erosion
• Rivers, streams, and runoff
Wave action is when waves hit the rocks and pieces of rock
break off.
In this picture the running water eroded the sides of
this canyon and created the V-shaped valleys.
Ice Erosion
• Glaciers
This is a picture of a glacier which carves out a U-shaped valley
where it flows dragging rocks and boulders along the way.
Wind Erosion
Mass Movements• Landslides, mudslides, slump and creep
This is a picture of a landslide. A type of mass
wasting.
This is a picture of an avalanche. It is similar to a landslide with ice and
snow instead of rock.
Mudslide
This is a diagram of creep. The hillside slowly slips over many
years from temperature or water.
Creep
In this picture the land has slumped
into the road below.
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