ROCKS

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ROCKS

• Mr. DeMarco

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The Main Concepts

• What are Rocks
• The Rock Cycle
• Igneous Rocks
• Sedimentary Rocks
• Metamorphic Rocks

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Rocks are mixtures of minerals..
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There are 3 major classes of rock.

• Igneous rocks form when hot molten rock material
  cools and hardens.

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Sedimentary Rocks

• Sedimentary rocks form when bits and pieces of
  other rocks are weathered and eroded away,
  accumulate (usually in a large body of water),
  and are cemented together.

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Metamorphic rocks..

• form when other rocks are altered by heat,
  pressure, and/or chemical action.

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The rock cycle begins with each of the 3 major
rock groups.
Igneous
Metamorphic
Sedimentary
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Igneous rock can weather and erode to from
sediments...
Igneous
Sediments
Metamorphic
Sedimentary
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Which can be cemented together to form
Sedimentary rocks
Igneous
Sediments
Metamorphic
Sedimentary
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These rocks can then melt to form magma...
Igneous
Sediments
Metamorphic
Magma
Sedimentary
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Which cools and hardens to form Igneous rock
Igneous
Sediments
Metamorphic
Magma
Sedimentary
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The igneous rock could also be heated /or
pressurized.
Igneous
Sediments
Metamorphic
Magma
Sedimentary
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to form a new Metamorphic rock.
Igneous
Sediments
Metamorphic
Magma
Sedimentary
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Or the Igneous rock could melt and cool to form a
new Igneous rock.
Igneous
Sediments
Metamorphic
Magma
Sedimentary
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The Metamorphic rock could also melt and cool to
form a new Igneous rock.
Igneous
Sediments
Metamorphic
Magma
Sedimentary
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The Metamorphic rock could also erode to form
sediments.
Igneous
Sediments
Metamorphic
Magma
Sediments
Sedimentary
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which is cemented together to form a new
sedimentary rock.
Igneous
Sediments
Metamorphic
Magma
Sediments
Sedimentary
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The sedimentary rock can be heated /or
pressurized to form a metamorphic rock.
Igneous
Sediments
Metamorphic
Magma
Sediments
Sedimentary
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The sedimentary rock can be eroded to form
sediments....
Igneous
Sediments
Metamorphic
Magma
Sediments
Sedimentary
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Which are cemented together to form new
sedimentary rocks.
Igneous
Sediments
Metamorphic
Magma
Sediments
Sedimentary
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Finally, the metamorphic rock can be heated and
pressurized.
Igneous
Sediments
Metamorphic
Magma
Sediments
Sedimentary
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to form a new metamorphic rock.
Igneous
Sediments
Metamorphic
Magma
Sediments
Sedimentary
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The Rock Cycle
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Igneous Rocks

• Igneous rocks form when hot liquid rock called
  magma (if it is deep within the earth) or lava
  (if it is near or at the earths surface) cools
  and hardens.

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Igneous rocks are classified as being Intrusive
of Extrusive

• Extrusive igneous rocks (aka Volcanics) form as
  lava cools and hardens at or near the earths
  surface.

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Intrusive (aka Plutonic)

• These rocks form deep in the earth as magma cools
  and hardens.

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Crystal size and cooling time...

• As minerals take form, molecules fall into
  place layer upon layer in a definite orderly
  pattern. Minerals which cool over a long period
  of time will therefore develop large crystals.

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Rapid cooling, however.

• does not permit the atoms to arrange themselves
  in an orderly pattern. Thus, rocks which cool
  quickly usually have a glassy or fine texture.

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Igneous rocks can be identified by their..

• Color - Is the mineral dark or light ? This
  color usually reflects the mineral composition of
  the rock
• Texture - Is the rock coarse grained (crystals
  are easily visible with the naked eye), fine
  grained (crystals are only visible with a
  magnifier) or glassy (no crystals are visible
  even under magnification) ?

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Use your Earth Science Reference Tables to
identify igneous rocks.
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If your sample is light colored..
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and is fine grained..
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The rock must be Rhyolite