Download Weathering & Erosion

Weathering
Weathering is the physical and
chemical breaking down of rock
material into smaller fragments
due to exposure to processes that
occur at Earth’s surface
Weathering occurs when rocks in the
lithosphere are UPLIFTED and is
exposed to the atmosphere,
hydrosphere, and biosphere
Weathering
 The most important agent involved in the
weathering of material is WATER
Two Types OF Weathering:

1) Physical
weathering is
breaking rock by
force into smaller
pieces of the SAME
material
ex: hitting,
scratching,
cracking
2) Chemical
weathering is the
chemical reaction
of water and
water vapor
breaking down
rock by changing
its chemical
composition
 The minerals that
make up the rocks
are changed into
another substance

4 Types of Physical Weathering
1) Frost action
 (ice wedging)
1.Water seeps into small cracks in rocks.
2.When the water freezes it expands
creating great pressure.
3.The crack widens and allows water to
seep deeper into the rock.
4.Alternating Freezing and Thawing
Examples of Frost Wedging :
Potholes

2) Plant action-
1.Tiny root hairs
seek out small
cracks and pits
in rock.
2.Once the root
hairs find a
place they grow
and expand.
3.The expansion
causes great
pressure and
cracks the rock.

3) Exfoliation
1. Rocks formed deep
in the Earth are
made under high
pressure.
2. When the pressure
is released the
rocks expand &
crack.
3. May also be caused
by alternate
heating and
cooling of rocks by
weather
conditions.
4. This is basically
the “peeling away”
of rock
Water
4) Abrasionrubbing by
other rocks
 Scraping,
grinding, and
wearing away
other rocks
during erosion

WIND
Types of Chemical Weathering
 Oxidation
 Hydrolysis (water)
 Carbonation (acid rain)

OxidationOxygen in the
atmosphere
chemically
reacts with
minerals.
ex.: rusting

Water
(hydrolysis)
Minerals are
dissolved in
water.
ex.: Halite,
calcite
Much of the time
these minerals
will end up as
clay

Acid- Carbonic
acid:
C02 dissolves in
rain water
forming a weak
acid.
This acid
dissolves the
calcium
carbonate
(calcite) in
limestones and
marbles

Acid Rain:
Sulfur Dioxide
in the
atmosphere
dissolves in
rain water
forming a
strong acid
(sulfuric acid).
Carbonation – Stalagtites and
Stalagmites (karst topography)
Carbonation – Karst Topography
 Karst Topography is the name given to a region
where the bedrock is easily chemically
weathered
 This leads to the rock weathering away and
forming sinkholes, caverns, disappearing
streams
Karst Topography
Differential Weathering
 Masses of rock do not weather uniformly due to
regional and local factors
 Results in many unusual rock formations
 Example: Bryce Canyon
Bryce Canyon National Park
Rates of weathering will be
influenced by:
Surface area exposed weathering occurs on the
surface. 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.
Rates of Weathering will depend on:
 Mineral
composition- some
minerals are more resistant
than others.
– ex.:Quartz is resistant to chemical
and physical weathering.
Where is the rock more resistant to
weathering?
Where is the rock least resistant to
weathering?
You might also see it like this…
You might also see it like this…
Rates of Weathering will depend on:
 Climatic
Conditions:
Cold and/or dry climates favor
physical weathering.
Warm and wet climates favor
chemical weathering.
Frost action works best in areas
where the temperature fluctuates
wildly.
Soil - The product of
weathering
 Soil-
rocks, minerals (mainly
sand and clay), and organic
material (regolith and
organic matter)
 Soil forms layers of different
characteristics called
horizons.
Soil Horizons