Download How Rocks are Formed

How Rocks are Formed
http://magma.nationalgeographic.
com/ngexplorer/0605/quickflicks/
Everywhere you look, you see ROCKS.
 The concrete high-rises are made from
limestone.
 The Cement you walked on this morning –
ROCKS
 The Mountains in the distance - ROCKS
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Bill Nye - ROCKS
http://www.youtube.com/watch?v=v3-JZQt1ws
 http://www.youtube.com/watch?v=tBk1mj9
6EX8&feature=related
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Only show second clip until 2:27
Three Families of ROCKS
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Scientists group rocks into three major
families, based on how they are formed.
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The three families are:
 Sedimentary
 Metamorphic
 Igneous
Igneous Rock
Forms when hot magma or lava cools and
becomes solid
 Magma is melted rock found deep below
Earth’s crust, where temperatures and
pressures are high.
 Lava is molten rock on Earth’s surface.
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More Igneous Rock
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Geologists classify igneous rock based on
whether it was formed above or below Earth’s
surface.
Rock that cooled below (in) Earth’s surface is
called intrusive rock. ie Granite.
Rock that forms when lava has cooled is called
extrusive rock. Volcanic rocks such as pumice
are extrusive.
The size of the crystal in igneous rocks depends
on how quickly the rock cooled.
Sedimentary Rocks
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is made from sediment and/or by chemical
reactions
Sediment is loose material, such as bits of
rocks, minerals, plants and animals.
Sediment slowly settles over sediment, forming
layers.
Sedimentary rocks are usually made in the
ocean and lakes where the larger, heavier
fragments settle first. Each layer of sediment is
squeezed together by the weight above it.
The process of squeezing together layers of
sedidment is called compaction.
Cementation
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The minerals in some rocks dissolve as water
soaks into the rocks. The dissolved minerals
form a natural cement that sticks the larger
pieces of sediment together.
Other sedimentary rocks, such as limestone, are
formed in water by a chemical change.
The three processes that make sedimentary
rocks are:
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Compaction
Cementation
Chemical Change
Sedimentary Rocks and Fossils
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Fossils are evidence of once-living organisms.
BC contains a wealth of fossils. Sedimentary
rocks throughout the province contain fossilized
shells, bones, scales, footprints, teeth and
leaves.
Fossils provide evidence of the environment
and the climate in which the animals or
plants lived.
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Scientists know that BC was once covered by tropical
forests because tropical plant fossils have been
discovered.
Yoho Valley
The fossils found in Yoho Valley (Eastern
BC) are so special that it has been
declared a World Heritage Site. It is home
to some of the most famous and unusual
fossils in the world.
 Burgess Shell
 Show Bill Nye at 2min
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http://www.youtube.com/watch?v=4ve7lUy5910
Types of Fossils
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The remains of plants and dead animals decay
and are destroyed quickly. When their remains
are protected from bacteria and scavengers their
bodies can be fossilized.
Actual Remains – very rare – an entire animal or
plant can be encased is amber, ice, natural
paraffin or tar.
Unaltered Hard Parts –
Occasionally the unaltered
bones of dinosaurs are
found
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Carbonization – In the process, all of the volatile
substances decay and leave behind a thin layer
of carbon. Both plants and animals can be
preserved by this method of incomplete decay.
Petrifaction – After death of the organism, the
organic matter starts to decay. Water containing
dissolved mineral soaks into every cavity and
begins to recrystallize. These fossils can be
made of silica, calcite, pyrite or limestone.
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Moulds and Casts – These are formed
when the animal or plant dies, decays and
leaves a cavity in the sediment.
Sometimes this cavity is not filled and
remains a mould. Usually, however, more
mineral matter is moved in by water and
fills the mould to form a cast.
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Trace Fossils – These are indirect
evidence of behaviour of the organism.
Trace fossils can include tracks, track
ways, eggs and nests, tooth marks,
imprints, trails, and burrows. Imprints are
external moulds of very thin objects, such
as leaves. Coprolites are fossilized feces.
Metamorphic Rocks
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Made when heat, pressure, or fluids change one
type of rock into another type of rock.
Can be made from igneous and sedimentary
rocks. Also from other metamorphic rocks.
The formation is a long and slow process!
Metamorphic rocks are always formed below the
surface of the Earth where heat an pressure are
always high.
More Metamorphic Rocks
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Hot, watery fluids can flow into igneous,
sedimentary or metamorphic rock and change
the rock both physically and chemically.
The original rock that is being changed is called
the parent rock.
Metamorphic rocks that have layers are said to
be foliated – thin, leaf like layers
When the mineral structure changes, the
metamorphic rock does not have layers and is
said to be non-foliated.