weathering means the process of breaking down rocks and …...two types of weathering: mechanical...
TRANSCRIPT
Weathering means the process of
breaking down rocks and other
substances at Earth’s surface.
Two Types OF Weathering:
Mechanical (Physical) Weathering is
When rock is physically broken into
smaller pieces (but still
have the same chemical composition).
Chemical weathering is
Breaking down rocks through chemical changes (different
composition -what its made of and physical makeup- how it
looks).
There are 5 Types of Mechanical
Weathering
Change in Temperature
Environmental, Frost Wedging
Changes in Pressure
Actions of Plants and Animals
Abrasion (wind, water, gravity)
1- Freezing and thawing of water.
(Ice/ Frost Wedging)-
The repeated freezing and
thawing of water found in
cracks of rocks.
As water flows into the cracks in
rocks it freezes and expands.
Common in mountainous regions.
2- Change in environmental temperature –
Thermal Stress
As temperatures rise a rock will expand or get
larger. As temperatures cool, a rock will contract
or get smaller. These changes in temperature weakens and cracks rock.
Release of pressure
As erosion carries away
rocks from the top of a
mountain it reduces
pressure on the rocks
below. This causes the
outer layer of rocks to
crack and flake off like
layers of an onion.
Plant action-
Plant roots grow in
cracks of rocks and pry
rocks apart.
Actions of Animals
Animals burrow in the ground and break apart
rocks.
Abrasion- rubbing by other
rocks.
Sand and other rock particles
carried by wind, water, ice, or gravity wear away rocks.
Abrasion
Water: moving water causes
rocks to tumble.
Rocks are usually
round and smooth.
Wind: Wind lifts small
particles – think sand blasting.
Gravity: Ex- Landslides
Can also occur with rocks in
glaciers – how??
Reactions with Oxygen (Rust)
Reactions with Acids (Acid precipitation
Reactions with Water
Reactions with Organism
Types of Chemical Weathering
Reaction with oxygen –AKA Oxidation-
Oxygen combines with water
to make rust. (Oxidation)
ex.: rusty bicycle
Acid precipitationBurning fossil fuels causes
sulfur, carbon, and nitrogen to
mix with water vapor in clouds
to form acid precipitation.
CO2
Carbon dioxide dissolves in rainwater to make
carbonic acid (weathers marble and limestone).
Water (ground water)Minerals are dissolved in water.
(minerals come from rocks that the
water is coming into contact wirh.
ex.: Halite, calcite
Living Organisms
Plants produce weak acids that dissolve rocks. Lichens
grow on rocks and make weak acids.
Rates of Weathering will depend on:
Surface area exposed - More surface exposed,
the faster the weathering will occur.
A full, solid block has the least surface area. The interior is safe from exposure.
A smashed piece has greatest surface area exposed. The interior can now be attacked.
Type of Rock - some rocks and minerals are
more resistant than others. – ex.:Quartz is resistant to chemical and physical
weathering. Slate tombstones weather slower than
marble tombstones.
Rates of Weathering will depend on:
Climate:
Cold and/or dry climates favor physical
weathering.
Warm and wet climates favor chemical
weathering.
Rates of Weathering will depend on: