Transcript The Rock Cycle - Enter Physics Locker

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Different types of rock
There are many different types of rocks in the world.
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Identifying rocks
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Identifying rocks: summary
type
examples
sedimentary
sandstone
and limestone
metamorphic
igneous
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marble and
slate
basalt and
granite
description
the softest rock type,
containing layers and
sometimes fossils
usually harder than
sedimentary rocks,
containing thin layers
and twisted fossils
usually the hardest rock
type, containing shiny
crystals
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Different rocks = different uses
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Pancake rocks in New Zealand
These limestone rocks at Punakaiki in New Zealand are known
as the Pancake Rocks. How do you think they were formed?
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What are sedimentary rocks?
chalk
limestone
sandstone
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Properties of sedimentary rocks
What are the properties of sedimentary rocks?
 Sedimentary rocks often
have layers showing the
deposition of sediment at
different time periods.
 Sedimentary rocks are made
of lots of small grains. These
grains are weakly held
together so the rocks are
often porous and may be
soft and crumbly.
 Sedimentary rocks often have
fossils trapped within them.
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Comparing ages of sedimentary rocks
Why are sedimentary rocks near the surface younger than
sedimentary rocks deeper down?
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Forming sedimentary rocks
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How are fossils formed?
When small rock fragments are transported to the sea, they
are deposited (sink) and form a sediment.
Dead creatures may become trapped within the sediment.
Over millions of years, the pressure of layers above
cements the sediment together.
This is how sedimentary rocks
like sandstone, mudstone
and limestone are formed.
As the body of the creature
decays away, its shape is left
imprinted in the rock, forming
a fossil.
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Formation by evaporation of water
Sedimentary rocks can also be formed from minerals that are
left behind when water evaporates.
 Some minerals are
dissolved in seas and lakes.
 Over millions of years these
seas or lakes dry up.
 As the water disappears,
the dissolved minerals are
left behind.
 Chalk and limestone,
common in the UK, can be
formed in this way.
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Which type of sedimentary rock?
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What are metamorphic rocks?
What has happened to the fossils and layers of particles in
these rocks?
The layers and fossils in these rocks have become squashed
and twisted.
What caused this?
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Formation of metamorphic rocks
Sedimentary rocks are turned into metamorphic rocks by the
extreme pressures and temperatures deep within the Earth.
These conditions change the structure of the rocks so that new
layers are formed.
heat
more heat
pressure
more pressure
Mixture of grains
in structure
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Heat and pressure
compress grains
Grains form
orderly layers
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Properties of metamorphic rocks
How are the properties of metamorphic rocks different from
sedimentary rocks?
 Metamorphic rocks often contain
layers of crystals, caused by the
effect of heat and pressure.
 Metamorphic rocks are usually
denser and harder than
sedimentary rocks.
 Metamorphic rocks sometimes
show wavy or zig-zag patterns
within the rock, caused by the
movements that led to their
formation.
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Examples of metamorphic rock
marble
soap stone
slate
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What is marble?
Marble is a hard smooth
rock made from sedimentary
limestone or chalk.
Because marble is extremely
hard it is an excellent building
material, and is also often
used for sculpture.
The different colours in
marble are caused by the
different combinations of
minerals in the limestone
from which it was formed.
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What is slate?
Slate is a grey rock with fine
grains made from sedimentary
volcanic ash or clay.
Because it is composed of
many distinct layers, slate
can be split into thin sheets.
During the 18th and 19th
centuries, thin sheet of slate
were used as a writing
surface. Slate sheets have
also traditionally been used
as a roofing material.
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What is mica?
Mica is a mineral that forms sheets that split smoothly, creating
almost perfect edges. This is because its atoms are arranged
in hexagonal sheets.
Mica usually appears very shiny.
Because of its stable atom arrangement
mica is very heat resistant. For this
reason it is often used in electrical
components such as capacitors, and as
an insulator in high voltage equipment.
Because mica can be split into flat sheets it is
also often used an alternative to glass window
panes in greenhouses etc.
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Which type of metamorphic rock?
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What are igneous rocks?
The name “igneous” comes from the Latin word for fire. Where
do you think this suggests that igneous rocks are formed?
Igneous rocks are formed in, and around, volcanoes.
What are some examples of igneous rocks?
basalt
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pumice
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How are igneous rocks formed?
Magma is a type of molten rock found deep underground.
Occasionally magma rises up through the Earth’s surface,
causing volcanic eruptions.
Igneous rocks are formed when the magma cools and solidifies.
 When magma cools
above the surface,
extrusive igneous
rocks are formed.
 When magma cools
below the surface,
intrusive igneous
rocks are formed.
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extrusive
igneous
rock
intrusive
igneous
rock
magma
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Properties of igneous rocks
How are the properties of igneous rocks different from
metamorphic and sedimentary rocks?
 Igneous rocks contain interlocking crystals that are held
together very strongly and make the rock hard.
 The crystals in igneous rocks
have a disorderly arrangement.
 The size of the crystals depends
on how quickly the igneous rock
solidifies.
 Igneous rocks never contain fossils.
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Crystal size in igneous rocks
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Crystal size in igneous rocks
Magma is full of minerals that turn into crystals under the right
conditions. Magma above the Earth’s surface cools quickly,
causing only small crystals to form.
This is how extrusive
igneous rocks like pumice
and basalt are made.
Magma below the Earth’s
surface cools more
slowly. There is time for
large crystals to grow as
the magma solidifies.
This is how intrusive igneous rocks like granite are formed.
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What is granite?
Granite is an intrusive igneous
rock. It is an extremely hard rock,
and contains many large crystals.
Granite is found all over the
world, but is commercially
quarried in India, Brazil, South
Africa and Scandinavia.
Because it is so hard granite is
often used as a flooring and
exterior cladding material, as well
as decorative material in worktops
in kitchens and bathrooms.
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What is pumice?
Pumice is a pale grey extrusive igneous rock, made up of very
small crystals.
It is formed when bubbles of
volcanic gas pass through
magma as it solidifies.
Because of this, pumice
contains many air pockets,
making it extremely light
and porous.
These lightweight properties mean that pumice is often used
as a component in breeze-block bricks. Its rough surface also
means that it is useful as an exfoliating (scrubbing) tool.
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What is basalt?
Basalt is a dark glassy extrusive
igneous rock.
Basalt contains very small
crystals, and is often found in
nature as huge columns of rock.
Traditionally basalt has been
used to make weapons, tools,
jewellery and carved sculptures.
Today basalt is also used in the
production of cement and road
surfaces.
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Working with rocks
Geologists are scientists
who study rocks.
They look at rocks and
use their observations to
draw conclusions about
the Earth.
 Some geologists study rocks to learn about the history of
the Earth and how it was formed.
 Some use their work to try to find deposits of valuable
minerals and fossil fuels.
 Others try to predict earthquakes, tsunamis and volcano
eruptions.
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Working with volcanoes
Scientists who study volcanoes
are called volcanologists.
They are skilled at monitoring
the changes in active volcanoes
that can indicate when an
eruption might occur.
Monitoring equipment is very
expensive and there are not
enough resources to keep check
on every active site in the world.
This can make studying volcanic
activity quite a challenge.
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Career link
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Find the rock
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Which type of rock am I?
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The rock cycle
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The rock cycle: in words
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The rock cycle: summary
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Glossary
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Anagrams
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Multiple-choice quiz
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From weathering to sedimentation
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