Transcript Classifying Rocks

Classifying Rocks
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Why would it be
important to classify
rocks?
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Ways to classify rocks
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Texture
Grain size
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Course or fine
Grain shape
Conglomerate -- well rounded
Breccia -- jagged grains
Grain Pattern
Layered, swirled, wavy, or random
No visible grain
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Ways to classify rocks
Mineral Composition
Same tests as mineral ID
Origins of rock
Igneous -- from molten rock
Two types
Extrusive -- liquid rock forced to cool out on
to the surface
Intrusive -- liquid rock cooling underground
Textures
Fine -grained -cooled quickly
Course grained -- cooled slowly
Glassy -- cooled extremely fast
Porphyritic -- rock cools in two stages usually
fast at first then slower in the end
Igneous cont.
Mineral composition
Low silica -- dark in color
High Silica -- light in color
Uses of igneous rocks
Tools and building material -- WHY?
Basalt is used in construction
Pumice used in cleaning
Obsidian is heated to form perlite
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Sedimentary Rocks
How do sedimentary rocks Form?
Three main processes all have to
happen
Erosion and deposition
 Break a rock down and hall the sediment to
a new place
Compaction
 Apply pressure to the sediment
Cementation
 Minerals in the sediment dissolve in water
and then recrystalize
 Or in other words gluing the rock back
together
Types of Clastic Sedimentary
Rocks
Shale -- particles of clay
Sandstone -- particles of sand
Conglomerates -- rounded pebbles
Breccias -- jagged edged pebbles
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Types of Organic
Sedimentary Rocks
Rocks that have high amounts of
organic material in them.
Coal
Swamp plants being compacted
underwater, over time
Limestone
Animals who have shells die, their
shells build up on the bottom, and is
compacted together over time.
What does this tell you about
Minnesota??
Chemical Sedimentary
Rocks
Form from
minerals being
dissolved in
water and then
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Dead Sea is an
example
Rocks From Reefs
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Formed from Coral growing
one on top of the other
Three types of Reefs
Fringing
Close to shore in shallow water
Barrier
Lie further out best known is the
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Atolls
Lie around an sinking volcanic
island
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Metamorphic Rock
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Classified by the grains that
make it up
Foliated -- splits in layers
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put together so it will not split in
layers
Uses for Metamorphic rocks
Very strong so it is good for building
materials
Many are sliced and polished to be
used in buildings for decoration
Example MN State Capital floors
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