Transcript Sedimentary rocks - Harpursville Middle School

ROCKS ROCK
• Classified on the basis of FORMATION
• 3 Types
– Sedimentary
– Igneous
– Metamorphic
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Rocks
• Composed of Minerals
– Mixtures
• 2 Types
– Monomineralic
– Polymineralic
• Of the 4000 minerals, only 8 of them make
up 90% of the crust.
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Sedimentary Rocks
• Rocks that form from the accumulation of
sediments, organic material or chemical
precipitates.
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Three main types
• Clastic
–Made from fragments of other
rocks
• Chemical/non-clastic
• Organic
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Clastic
(also known as fragmental)
• Classified on the basis of grain size
• Formation–Compaction (Pressure)
–Cementation (glued)
Examples
–calcite
–silicate
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1. Layers of sediments accumulate
2. Pressure squeezes lower layers
3. Sediment becomes compacted and
cemented into rock
Pressure =
Limestone
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Pressure =
shale
Pressure =
Sandstone
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Non-clastic (chemical)
sedimentary rocks
• Formed from
evaporation of water
– Examples
• limestone
• Halite
• Also known as
evaporites
• Precipitates also
occur
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Organic Sedimentary Rocks
• Formed from the remains of
former living things
–Example: coal
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Sedimentary Rocks
• Chemical and organic sedimentary
rocks identified primarily by
composition and texture (grain size)
• Sedimentary rocks form relatively
close to the Earth’s surface
 Why?
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Sedimentary Rocks
• All clastic
sedimentary rocks
are formed in
horizontal layers
Why do you think
this is so?
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Bedding in Sandstone and Shale,
Utah
Crossbedded Sandstone, Zion Natl.
Park, Utah. Formed by Sand dunes
deposited by wind
Graded Bedding
Sedimentary Rocks
• Sedimentary rocks sometimes
contain fossils
–Igneous and metamorphic rocks
almost never do
Why not?
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Sedimentary Rocks
• Lake and ocean environments
produce different sedimentary
rocks
–Examples:
• Limestone
–Forms in oceans
• Sandstone
–Forms in water near land
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 Use your ESRT to answer the following questions.
• What is the composition of rock salt?
• What is the size range of the grains in
sandstone?
• Draw the map symbol of shale
• Which is made of rounded fragments,
conglomerate or breccia?
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