Transcript The Forces of Weathering and Erosion

Weathering
Weathering
And
And
Erosion
Erosion
Weathering
The 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
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
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
1908
to
1969
Acid rain has eaten away this
limestone statue.
Acid Rain
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.
Erosion
There are many kinds of Erosion.
Here are a few:
• Wave Action
• Avalanche
•Creep
• Running Water
•Glaciers
• Rock Fall
• Landslides
• Slump
• 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.