Download Mechanical Weathering - Doral Academy Preparatory

Weathering
What is weathering?
The process that breaks
down rock into smaller
pieces, called sediments.
Not to be
confused with
WEATHER!
There are two types
of weathering:
Mechanical
Weathering
Chemical
Weathering
(physical)
Rocks are physically
broken into smaller
pieces.
Rocks are broken down
through chemical
changes.
The rate of weathering is affected by climate.
Mechanical happens faster in the cold weather.
Chemical is faster in warm weather.
Forms of Mechanical Weathering
Ice Wedging
Exfoliation
Abrasion
Plants and animals
Ice Wedging
(a.k.a. Frost wedging)
The cycle of water freezing and thawing in the cracks
of rocks, causing the rock to break.
Click the picture for ice wedging animation!
Exfoliation
Pressure causes rocks to crack and “peel’ away in slabs.
Abrasion
Sediments carried by wind or water rub against other
rock and wear it down. Like sandpaper!
Plant Wedging
Plant roots grow large and break apart rock.
Animals
Animals burrow into the ground and
loosen sediment and soil.
Surface Area of Rock
As rock is broken
apart by mechanical
weathering, the
amount of rock
surface area
exposed to air and
water increases.
These smaller
pieces will be
weathered faster
than a larger piece.
EXIT SLIP
1. What is weathering?
2. How do mechanical weathering and chemical weathering
differ?
3. What type of weather conditions would increase the rate
of chemical weathering?
4. The diagram shows the process of
ice wedging. Explain how this
process physically weathers rocks.
5. How can plants and animals
contribute to the mechanical weathering process?
Forms of Chemical Weathering
Oxidation
Dissolution
Hydrolysis
Organic Acids
Oxidation
When materials that
contain iron are exposed
to oxygen and water, they
become a reddish color.
Ayer’s Rock, Australia
Dissolution
Carbonic acid in rain dissolves rock. This
can form caves and cause sinkholes.
Hydrolysis
Water combines with the minerals in rock and
cause a chemical change.
If water combines with the mineral feldspar,
clay is formed.
Organic Acids
Plant roots give off acids that dissolve rock.
EXIT SLIP
6. Oxidation occurs when materials that contain iron are
exposed to what two compounds?
7. Dissolution can form sinkholes. Explain the process of
dissolution.
8. How do plants and animals chemically weather rocks?
Can you tell which
mountain is older?
What is soil?
A mixture of weathered rock, decayed organic
matters, mineral fragments, water, and air.
Factors Affecting Soil
Formation