Download Just remember, oldest is at the bottom because it was deposited first

Just remember, oldest is at the bottom
because it was deposited first
Which
fossils are
the oldest
in this
diagram?
This is
called
relative
fossil
dating.
There are two main types of
weathering
•  Chemical weathering:
•  Mechanical
the chemical
Weathering:
the breakdown of breakdown of rocks
and minerals into new
rock into smaller
pieces by physical substances (ex:
oxygen, water, acid
means (ex: ice,
rain)
water, gravity,
plants)
Mechanical Weathering:
the physical breakdown of rocks
Rusting: An example of chemical weathering
Some of the effects of Erosion and
Weathering
•  h#p://www.youtube.com/watch?v=n1cCs9
S5EKc>
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•  h#p://www.youtube.com/watch?
v=w40JgaKNihY&feature=related>
>
Mudslide
How (specifically) does this
stuff get loosened before it
moves?
Mechanical Weathering: Frost Wedging
•  When water seeps into a crack in a rock during warm
weather and then freezes during cold weather, it
expands.
•  And when it expands, it pushes against the sides of the
crack, forcing it to open wider.
•  This process is called frost (ice) wedging.
Ice/ Frost Wedging
Cracks in rock due to ice
Frost Wedging Video
http://goo.gl/K9W4x
Mechanical Weathering: Abrasion
•  Abrasion: the action of rocks and
sediments grinding against each other and
wearing away exposed surfaces
•  Caused by wind, water, and gravity
•  Wind blows against exposed rock, the
sand eventually wears away the rock s
surface
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Mechanical Weathering:
WIND, WATER and GRAVITY
•  Water: When rocks and pebbles roll along the
bottom of swiftly flowing rivers, they bump into
and scrape against each other.
•  They eventually can become river rocks.
How weathered is it?
Which piece is more weathered, left
or right?
Mechanical
Weathering:
WIND, WATER
and GRAVITY
•  Gravity: As rocks are
pulled down by
gravity, they can start
falling down
mountains. As the
rocks hit each other,
they rub against each
other causing
abrasion to occur and
leading to the
weathering of rocks.
Mechanical>Weathering:>PLANTS>
•  Plants often send
their roots into
existing cracks in
rocks.
•  As the plant gets
bigger, the force of
the expanding root
becomes so strong
that the crack is
made larger.
Biological Weathering (plants)
Mechanical Weathering: ANIMALS
•  Almost any animal
that burrows
causes mechanical
weathering
•  These may include
animals like ants,
mice, coyotes, and
rabbits
Animals burrowing home in rock
Chemical Weathering: WATER
•  Many>types>of>rock>can>be>dissolved>by>water>
•  Even>hard>rock,>like>granite,>is>broken>down>
by>water>
•  It>may>take>a>few>thousand>years>
The decay of underground rock,
forming sinkholes
•  h#p://www.nachi.org/images10/Guatemala9
Sinkhole.jpg>
Decayed Tombstone
Change in rock s mineral
composition
Chemical Weathering: ACID RAIN
•  Acid precipitation: precipitation that contains acids
due to air pollution
•  Precipitation such as rain and snow is naturally
acidic and contains carbonic acid
•  These acids can slowly break down rocks and other
matter
Chemical Weathering: ACID RAIN
continued
•  When fossil fuels
are burned, they
give off gases,
and when these
compounds
combine with
water in the
atmosphere, they
can fall back to
the ground in rain
or snow
Chemical Weathering: Acidic waters
•  Create limestone caves!
Chemical Weathering: AIR
•  In rocks that contain
iron, oxidation (rust)
may occur
•  Oxidation is a
chemical reaction in
which an element
combines with
oxygen to form an
oxide i.e. rusts
This%is%why%clay%in%North%
Carolina%is%red,%because%the%
iron%in%our%clay%has%rusted%
Real life example:
Devil s Tower (Wyoming, USA)
This used to be a volcano
Left: What it used to look like/ Right: What is
looks like now
Differential Weathering:
•  Not all rocks weather at the same rate
•  Some are more resistant to weathering
(tougher to break down)
•  Devil's Tower is an amazing example of
differential weathering. All that remains
of the volcano today is this central plug
of resistant lava that forms the tower.
Another example of differential weathering
Bisti Badlands – New Mexico
Weathering Lab
•  One partner should break 2 Smarties into
chunks, the other partner should take out
two Smarties candies
•  Make sure you are ready to record time!
• Drop your 2 solid pieces or chunks of
2 Smarties into your cup of acid
•  You can eat the rest of your pack ☺
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>
Create a Most Wanted Poster
1.  Pick a type of
mechanical or
chemical weathering
2.  Put on your poster
what crime it s
committed (i.e. it
destroyed a rock)
3.  Draw a picture and
say what the reward
is
Exit Ticket
1.  How>can>you>tell>which>fossil>is>older?>
2.  What>are>the>different>types>of>mechanical>
and>chemical>weathering?>
3.  Does>everything>weather>at>the>same>rate?>
4.  Does>size>make>a>difference>in>how>
something>weathers?>
5.  Is>there>a>way>to>tell>how>weathered>a>piece>
of>rock>is?>
Bill Nye on Rocks and
Weathering
h#ps://www.youtube.com/watch?
v=9Xv1DoqkARQ>