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Weathering is the process
that breaks down rock and
other substances at the
Earth’s surface.
Heat, cold, water, and ice
all contribute to
weathering.
Repeated freezing and
thawing for example can
crack rock apart into
smaller pieces.
Weathering of rock creates
sediments which can form
rocks, sand, and soil.
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The forces of weathering
breaks rocks into smaller
and smaller pieces. Then
the forces of erosion
carry the pieces away.
Erosion is the movement
of rock particles by wind,
water, ice, or gravity.
Weathering and Erosion
work together to wear
down and carry away the
rocks at the Earth’s
surface.
Erosion Video-How the
Earth Was Made
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Weathering and erosion
together can form things
like:
Caves
Canyons
Valleys
Arches
Steep Cliffside's
Remember this is
primarily caused by
wind, water, and gravity.
Erosion and Weathering
Photo Gallery
 Through
erosion a
river creates valleys,
waterfalls, flood
plains, and meanders
(loop like bend in a
river)
 Grand Canyon
Formation
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Both weathering and
erosion produce
sediment.
Deposition is the process
in which these new rock
sediments are laid down
in new locations.
So collectively erosion
and weathering break
down rock and
deposition relocates the
new sediments into
layered rocks or
sedimentary rock.
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Mechanical Weathering
occurs when rock is physically
broken into smaller pieces.
Mechanical weathering
breaks rocks into pieces by
freezing and thawing, growth
of plants, actions of animals,
and abrasion.
Abrasion is the grinding away
of rock by rock particles
carried by water, ice, wind, or
gravity.
Mechanical Weathering works
slowly but over long periods
of time it wears down whole
Mountains
Mechanical Weathering in
Ireland
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Chemical Weathering is
the process that breaks
down rock through
chemical changes.
The agents of chemical
weathering include
water, oxygen, carbon
dioxide, living
organisms, and acid rain.
Chemical Weathering
produces rock particles
that have a different
mineral makeup from the
rock they came from.
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Over time many rocks will
dissolve in water.
Rock that contains iron will rust
through the process of
oxidation.
Carbon Dioxide becomes
dissolved in rainwater and in
water that sinks through air
pockets in the soil. The result is
a weak acid called carbonic
acid which can easily weather
marble and limestone.
Burning coal, oil, and gas can
pollute the air with sulfur,
carbon, and nitrogen
compounds. These compounds
react chemically with the water
vapor in clouds to form acids.
 The
rate of
weathering usually
depends on the type
of rock and the local
climate.
 Chemical weathering
occurs faster at
higher temperatures.
Usually were the
climate is hot and
wet.
Gravity is the force that
moves rock and other
materials downhill.
 Mass movement of
rocks or sediments can
be fast or slow.
 The different type of
mass movements
caused by gravity
include landslides,
mudslides, slump, and
creep.
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Most destructive kind of
mass movement is a
landslide.
Landslides occur when
rock and soil slide
quickly down a steep
slope.
Landslides are common
when road builders have
cut highways through
hills or mountains.
Hawaii Weathering and
Erosion
 Mudflow
is the rapid
downhill movement
of a mixture of water,
rock, and soil.
 Mudflows often occur
after heavy rain
 The amount of water
in a mudflow can be
as high as 60%.
 Slumps
occur when a
mass of rock and soil
suddenly slips down
a slope.
 Unlike a landslide the
material in a slump
moves down in one
large mass.
 Caused by gravity’s
pressure over time.
 Creep
is the very
slow downhill
movement of rock
and soil.
 Creep often results
from the freezing and
thawing of water in
cracked layers of
rock beneath the soil.
Scientists use the Law
of Superposition to
determine the relative
ages of sedimentary
rock layers.
 According to the Law of
Superposition, in
horizontal sedimentary
rock layers the oldest
layer is at the bottom.
Each higher layer is
younger than the layers
below.
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The law of uniformitarianism
states that all geologic
phenomena may be explained as
the result of existing forces
having operated uniformly from
the origin of the earth to the
present time.
This means the way rocks
form and the way the plates of
the earth move currently is the
wave they have always moved
and behaved since they
formed.
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Lava that hardens on the
surface is known as an
extrusion.
The rock layers below and
around an extrusion are
always older then the
extrusion.
Beneath the surface, magma
may push into bodies of rock.
There, the magma cools and
hardens into a mass of
igneous rock called an
intrusion.
An intrusion is always younger
then the rock around it and
below it.
 An
unconformity is a
gap in the geologic
record.
 An unconformity
shows where some
rock layers have
been lost due to
erosion.
Most elements are
stable, they do not
change under normal
conditions.
 Some elements exists
in forms that are
unstable. Over time
these elements break
down or decay, by
releasing particles and
energy in a process
called radioactive
decay.
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The rate of decay of each
radioactive element is
constant.
Elements have a half life’s this
is what it takes for half of the
radioactive atoms to decay.
Geologists use radioactive
dating to determine the
absolute age of rocks.
Geologists compare how
much of the element is left
compared to how much is
normally there under normal
conditions. Since they know
the half-life of elements they
can then deduce the actual
age of the rocks.
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Most particles or elements of
carbon have an atomic mass of
12.011 there are some isotopes
of carbon that have a larger
atomic mass, for example
carbon 14, which is found in
most organic material.
We us the isotope carbon 14 to
tell us the relative age of rocks,
if they contain organic material.
For example we know the half
life of carbon 14 is 5,730 years.
So if we find a rock that has
carbon and it’s atomic mass is
approximately 7 then 5,730
years have passed since it
originally formed.
Soil is a mixture of
decayed organic
material and minerals.
 The organic material
comes from dead
plants, such as last
years leaves.
 The minerals come
from rocks
underground typically
known as bedrock.
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 Geologists
believe
that the Earth is
roughly 4.6 BILLION
YEARS OLD!!!!!!!
Have you ever skidded
on a rug that wrinkled
up as your feet pushed
it across the floor?
 Rock stressed by
compression may bend
slowly without
breaking creating
folds.
 Folding can cause the
youngest rock to not
always appear on the
top of rock formations.
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Mountain building can
be caused by folds and
faults.
This process takes
millions of years!!!
Faults usually occur
along plate boundaries
where the forces of plate
motion compress, pull, or
shear the crust so much
that the crust breaks.
Faults can also cause
layering where the
youngest rock is not
always on top.