Transcript Weathering and Erosion

Weathering and Erosion
Weathering
• The process that breaks down rocks and
other materials of Earth’s crust into smaller
pieces.
Erosion
• The removal of rock particles by wind,
water, ice, or gravity.
Weathering and erosion work
together to wear down and carry
away rocks on Earth’s surface
Avalon
Wildwood
Weathering
Weathering can happen two
different ways
- Physical and Chemical
Physical Weathering
• Rock is physically broken down into
smaller pieces
There are five types of physical
weathering
1. Freezing and thawing
Frost Wedging
Frost Heaving
2. Plant Growth
3. Animal Actions
Burrowing of Animals
4. Friction and impact
River rocks are
rounded and
smoothed due to the
repeated tumbling
along the river bed as
they roll downstream
5. Temperature Changes
Rocks expand (get
bigger) when they
are hot, and contract
(get smaller) when
they are cold.
This brick wall has expanded and
there is a visible crack
Chemical Weathering
• The process that breaks down rock
through chemical changes.
There are five types of chemical
weathering
1. Water
• Water weathers rock by dissolving it
2. Oxygen
• Iron combines with
oxygen in the
presence of water in
a processes called
oxidation
• The product of
oxidation is rust
3. Carbon Dioxide
• CO2 dissolves in rain water and creates
carbonic acid
• Carbonic acid easily weathers limestone
and marble
4. Living Organisms
• Lichens that grow on rocks produce weak
acids that chemically weather rock
5. Acid Rain
• Chemicals from burning coal, oil and gas
react chemically with water forming acids.
• Acid rain causes very rapid chemical
weathering
All this weathering can create
interesting landforms
Formation of Devil’s Tower,
Wyoming
http://www.youtube.com/watch?v=Hsh3_ZMKq-A
Karst Topography
• A type of
landscape in rainy
regions where
there is limestone
near the surface
• Created by
chemical
weathering of
limestone
Features of Karst: Sinkholes
Features of Karst: Caves
Features of Karst: Disappearing
Streams
Erosion
Erosion moves rock particles using
four different methods
1. Water Erosion
• Rivers, streams, and runoff
http://www.youtube.com/watch?
v=ReCt2AcydCg&feature=relate
d
2. Ice Erosion
• Glaciers
http://www.youtube.com/watch?v=X
OGbOOaPHsw&feature=related
3. Wind Erosion
http://www.youtube.c
om/watch?v=mecKn
kc9qMk
4. Gravity
• Landslides, mudslides, slump and creep
http://www.youtube.com/watch?
v=ZVjr4mii3cE&feature=player_
embedded#!
Summary
• Weathering breaks down rocks
– It can be physical (ice, plants, animals,
friction, temperature change) or chemical
(water, oxidation, acid rain, carbon dioxide,
living organisms)
• Erosion moves the rocks
• Together they produce soil
http://teachertube.com/viewVideo.php?video_id=20814&title=Weathering_and_Erosion_b
Soil
• Soil is made from
rocks, minerals
(mostly sand and
clay), and organic
materials
• Soil forms layers of
different
characteristics called
horizons
What is soil?
• Soil is a material that forms the crust of the
earth.
• It comes from the weathering of rocks and
decomposition of organisms.
• It is formed very slowly.
What’s in soil?
•
•
•
•
Minerals
Organic matter
Air and water
Living organisms
Soil is found in layers called
horizons
Soil
O horizon
(green)
• O = Organic
• The top,
organic layer
made up mostly
of leaf litter and
humus.
• Humus is
decomposed
organic matter.
A horizon
(dark brown)
• A = Topsoil.
• Dark colored
• Where seeds
germinate and
roots grow. This
is generally the
most productive
layer of soil.
B horizon
(light brown)
• B = Subsoil
• Lighter colored
• Contains clay
and mineral
deposits (iron,
aluminum, etc)
C horizon
(tan)
• C = Parent
Material
• Layer of large
unbroken rocks
R horizon
(black)
• R = Bedrock.
• The solid rock that
is under the soil
• Areas with a lot of humus and topsoil are
great for growing plants.
Mosaic
of closely
packed
pebbles,
boulders
Weak humusmineral mixture
Alkaline,
dark,
and rich
in humus
Dry, brown to
reddish-brown, with
variable accumulations
of clay, calcium
carbonate, and
soluble salts
Desert Soil
(hot, dry climate)
Clay,
calcium
compounds
Grassland Soil
(semiarid climate)
Forest litter
leaf mold
Acidic
lightcolored
humus
Humus-mineral
mixture
Light-colored
and acidic
Light, grayishbrown, silt loam
Iron and
aluminum
compounds
mixed with
clay
Tropical Rain Forest Soil
(humid, tropical climate)
Acid litter
and humus
Humus and
iron and
aluminum
compounds
Dark brown
firm clay
Deciduous Forest Soil
(humid, mild climate)
Coniferous Forest Soil
(humid, cold climate)
Soil lab online
• Tomorrow you will meet in the computer
lab (229) and compare rainfall amounts to
topsoil depths.
• You will learn how rainfall affects topsoil
depth.