Weathering The breaking down of rock into smaller pieces that remain next to each other Weathering forms sediments There are two types of weathering Mechanical Physical Chemical Mechanical Weathering ID: 614198
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Slide1
What is Weathering?Slide2
Weathering
The breaking down of rock into smaller pieces that remain next to each other.
Weathering forms sediments.
There are two types of weathering.
Mechanical (Physical)
ChemicalSlide3
Mechanical Weathering
Mechanical weathering is the
breaking down of rock without any change in the chemical composition of the rock
.
Sometimes called “
physical
” weathering
Rock is
torn apart
by physical force, rather than by
chemical breakdown
Smaller pieces
do not move
to a new location, but remain next to one another until erosion carries them away
There are 4 main types of Mechanical Weathering
Ice Wedging
Exfoliation
Thermal
BioticSlide4
Ice Wedging
Water
enters the cracks in rocks, and then
freezes and expands
about 10%.
The ice puts stress on the walls around the cracks and causes cracks to
get deeper and wider
.
Water can flow deeper into the rock as
the ice thaws
. As the cycle repeats, rocks grow
weaker
over time.
Along the cracks, the rock will
break into angular pieces
over time.Slide5
Ice WedgingSlide6
Exfoliation
Rocks formed
deep in the Earth
are under a huge amount of
pressure
.
When the overlying rock
is removed by erosion
,
pressure
is released and the once buried rocks are exposed.
Expansion
occurs along the outer parts of rocks. This stress will cause fractures to form parallel to the rock surface.
Along the exposed rock fractures,
sheets of rock
will break away.Slide7
ExfoliationSlide8
Thermal
Thermal
weathering
is
a result of extreme changes in temperature that causes the expansion or contraction of rock.
Common in
deserts
, where it is hot in the day and cold at night; different minerals expand and contract at different rates causing the rock to
split
The outer layers
peel off
into thin sheets.Slide9
ThermalSlide10
Biotic
Biotic weathering is caused by
living organisms
.
Most often,
plant roots
are the cause.
They act as a
wedge
, widening and extending the cracks.
Digging animals
can also cause weathering.Slide11
BioticSlide12
Chemical Weathering
Chemical weathering
is the breaking down of rock into smaller pieces because of chemical changes within the rock.
Rock reacts with
water, gases, and solutions
(may be acidic); these reactions will add or remove elements from minerals.
Rocks fall apart because the
bonds holding them together
are broken down by chemical reactions
.
There are 4 main types of Chemical Weathering
Oxidation
Hydrolysis
Carbonation
BioticSlide13
Oxidation
When oxygen
combines with other elements in rocks
and chemical reaction known as oxidation occurs and new types of rock are formed.
The new types of rock are
easier
to break apart because they are much softer than the original substances.
A reddish-brown coloration on the surface is called
rusting
.Slide14
OxidationSlide15
Hydrolysis
Hydrolysis
is the weathering reaction that occurs when
water and chemical compounds
in a rock meet.
This results in the
decomposition
of the rock surface by forming new compounds
.
Most common reaction is the
hydrolysis of
feldspars producing clay (kaolinite)Slide16
HydrolysisSlide17
Carbonation
When
carbon dioxide
reacts with water or rain, carbonation occurs and a weak
carbonic acid
is formed.
This is the same acid found in
soda
.
The acid is too weak to
harm
plants and animals, but slowly causes feldspars and limestone to decompose.
New types of
softer substances
are formed within the rocks.Slide18
CarbonationSlide19
Biotic
Lichens and similar plants
live on the surfaces of rocks.
Plants lower the local
pH
to make it
more acidic
.
Their
roots
give off a
chemical
that
dissolves
rocks and minerals.Slide20
Biotic