8G Rocks and weathering
8G Rocks and
weathering
Rocks and minerals
Erosion
Deposition
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8G Rocks and weathering
Rocks and minerals
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8G Building the Earth
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8G Rock band
The rocks we see all come from the thin, solid crust
on the outside of the Earth.
They are all made of minerals.
A mineral is a chemical found in a rock.
Most minerals are mixtures of different chemicals.
Marble
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Granite
Slate
8G Weathering
Rock does not last forever. Look at the picture here –
how can you tell that the rock has been damaged by
the environment?
What might have done this damage?
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8G Freeze-thaw
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8G True or false?
Are these statements true or false?
1. Water expands when it freezes.
TRUE
2. Rocks contract during the day and expand
at night.
FALSE
3. Acid rain dissolves some rocks.
TRUE
4. Soft rocks weather more quickly than
harder rocks.
TRUE
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8G True or false?
Are these statements true or false?
1. Plants cannot cause rocks to crumble.
FALSE
2. Granite gravestones weather more quickly
than those made of limestone.
FALSE
3. Rocks can be weathered by repeated
heating and cooling.
TRUE
4. Acid rain is made when oxygen dissolves
in falling rain.
FALSE
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8G Rocks and weathering
Erosion
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8G Break it, move it, shape it!
Rocks may last a long time but they do change.
Even the toughest rocks can be broken down to
smaller particles. We call this process weathering.
Small particles may be moved around to new
areas. We call this transportation.
The two processes together (weathering and
transportation) are called erosion.
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8G Move it! Fast!
What are the conditions that give the biggest rate of
movement?
Amount of
water
Size of
sediments
Speed of water
flow
small
small
slow
medium
medium
medium
large
large
fast
Where would you find these conditions?
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8G Move it! Fast!
What are the conditions that give the slowest rate of
movement?
Amount of
water
Size of
sediments
Speed of water
flow
small
small
slow
medium
medium
medium
large
large
fast
Where would you find these conditions?
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8G Rocks and weathering
Deposition
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8G Settle down!
As the water carrying sediments slows down, the
sediments fall out of suspension.
The sediments make a layer on the bottom of a
lake or river.
New sediments are laid down on top, pressing the
ones below together.
Over thousands of years the sediments become
stuck together to make a soft rock – sedimentary
rock.
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8G Age of sediments
Which rock type is oldest? How can you tell?
The fossil in layer 4 is part of an ammonite from
180 million years ago. What does this tell you about
the age of layer 3?
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8G Sedimentary facts
True or false?
1. Sedimentary rocks take thousands of
years to form.
TRUE
2. Sedimentary rocks never form in layers.
FALSE
3. Sedimentary rocks often contain crystals.
FALSE
4. Salt crystals stick the grains in
sedimentary rocks together.
FALSE
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8G Sedimentary facts
True or false?
1. The first process involved in making
sedimentary rocks is called weathering.
TRUE
2. Deposition lays down sediments.
TRUE
3. It is unlikely that you would find a fossil in
a sedimentary rock.
FALSE
4. Chalk is a sedimentary rock.
TRUE
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8G Water on Mars?
This image shows the surface of Mars. It’s obvious that
water flowed here once! Or is it? What do you think?
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8G Craters on the Moon
Which of these craters is the oldest? How can you tell?
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8G Why so sharp?
The features on the Moon’s surface
are very sharp.
This is because there
is no water to erode
away the edges.
This is because the
low gravity stops rocks
from crumbling.
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Which is correct?
Why?
8G Rock quiz
1. The crust of the Earth is…
a) very thin compared with the layers underneath
b) very thick compared with the layers underneath
c) missing under the Pacific Ocean.
2. Sediments are…
a) the small fragments of rocks produced by weathering
b) the water currents in a fast flowing stream
c) always formed a long time ago.
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8G Rock quiz
3. Weathering is…
a) the breakdown of rocks by the environment
b) the building up of rock by piling sediments up in layers
c) predicting the likelihood of rainfall in a particular area.
4. Acid rain dissolves limestone better than granite
because…
a) limestone contains more calcium carbonate than
granite
b) limestone is a softer rock than granite
c) granite is waterproof but limestone is not.
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8G Rock quiz
5. Fossils are…
a) remains of dead plants or animals preserved in rock
b) made when granite is eroded
c) old teachers.
6. Which stream would carry the most sediments? Why?
a) a large river in flood
b) a small river flowing very quickly
c) a large river flowing slowly.
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