Download A Closer Look At Rocks

A Closer Look At Rocks
Do you remember the names of the 3 rock
families?
That’s Right!
 Igneous
 Sedimentary
 Metamorphic
Let’s Take a Closer Look at Igneous Rocks!
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These rocks are formed from either magma or lava
Intrusive igneous rock are formed inside the Earth from magma
– Usually take a long time to cool and have large crystals
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Extrusive igneous rock is formed on the Earth’s surface from lava
– Take a shorter time to cool and have small crystals
 Igneous
rocks are usually the hardest type of rock and last
longer than any other type of rock
 These
Sedimentary Rocks
rocks are formed from sediment
– Rock particles, decaying animals, plants and minerals
– Layers can be made on land or in water
 Particles
are moved around by water, wind and ice
Forming Loose Sediment into Rock
Rock particles get pressed together forming layers that
make up sedimentary rock
 Some small particles may be formed into rock by
pressure alone examples silt and clay
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In some sedimentary rocks the particles are held
together by minerals that have crystallized acting as a
cement
Metamorphic Rock
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Heat and Pressure Change Rocks
When a rock changes by heat and or pressure it
undergoes metamorphism
– The original igneous or sedimentary rock is called the parent
rock
– It changes into a metamorphic rock
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A metamorphic rock can also be a parent rock
– It changes into another metamorphic rock
Metamorphism
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Pressure causes the minerals to flatten out
It remains as a solid
Rocks DO NOT MELT when they undergo metamorphism
Recrystallization
Heat and pressure break bonds. Then the atoms rejoin
in a new way and form new bonds
 Crystals can become larger as more atoms join the
crystal structure
 Atoms can combine in a different way and new minerals
can be formed.
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Metamorphic Rocks Develop Bands of Minerals
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Foliation
Arrangement of minerals in flat or wavy parallel bands
Foliated rocks
Foliation occurs when a rock is under pressure
This develops when minerals flatten out
Non-foliated rocks
May not display foliation because it is made up of one mineral
Example – marble
It may not have been subjected to high pressure