Igneous Rocks

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Igneous Rocks

• Earth Science
• Ms. Cammarano

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Igneous Rocks- Fire Rocks

• Igneous rocks are formed by the crystallization
  of molten rock .
• Molten is liquid minerals and
• rocks.

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Igneous Rocks

• Liquid rock BENEATH the surface is called MAGMA
• Liquid rock ABOVE the surface is called LAVA

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Intrusive Igneous Rocks

• When igneous rocks form BENEATH the surface from
  magma it is called INTRUSIVE

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Extrusive Igneous Rocks

• When igneous rocks forms ABOVE the surface from
  lava it is called EXTRUSIVE

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How Do We Identify Igneous Rocks?

• ESRT!!!
• Identification is done by looking at the CRYSTAL
  SIZE and TEXTURE within the rock.
• When magma or lava cools it forms a network of
  interlocking crystals

Interlocking Crystals
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Crystal Size- Grain Size

• The size of the CRYSTALS in an igneous rock
  depends on the conditions under which it was
  formed

Large Crystals
NO CRYSTALS
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Slow Cooling Magma- Intrusive

• When magma cools slowly underground, INTRUSIVE,
  large crystals are formed.
• If it cools slow CRYSTALS will GROW!!!

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Fast Cooling Lava- Extrusive

• When lava cools quickly above ground, EXTRUSIVE,
  smaller crystals are formed.
• If it cools too fast CRYSTALS WONT LAST!

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Fast- wont last

• Cools too fast--- small crystals- small cookies

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Slow- Crystals Grow

• Slow- time to grow- Big Cookies!

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No Crystals

• If lava cools quickly no crystals are formed.
• This is called Non-Crystalline. Crystal need
  time to form.

No Crystals!
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Texture

• Big crystals have a rough, Coarse texture.

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Fine texture

• Small crystals have a smooth, FINE texture.

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No Crystals

• Glassy
• Vesicular- Gas Pockets pop and leave holes in the
  rock.

Gas Pocket
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Environment of Formation

• Answer the following questions.
• If the rock is a non-crystalline with a glassy
  texture the rock was formed in a ________
  environment.
• Extrusive (Volcanic)
• A rock that has a coarse texture and large
  crystals (1mm to 10mm) is_________.
• Intrusive (Plutonic)

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Color and Composition

• Felsic Rocks that are light in color and have a
  low density.
• Obsidean, Pumice, Rhyolite, Granite, Pegmatite
• Mafic Rocks that are dark in color and have a
  high density.
• Basalt, Scoria, Gabbro, Peridotite

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Minerals

• Use the ESRT to find the rocks mineral
  composition by reading the table straight down
  from the rocks name.

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Questions

• The diagram below represents four rock samples.
  Which rock was formed from slow cooling in a
  plutonic environment?
• 4- Large interlocking
• Crystals. Slow crystals
• Grow!

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Questions

• The diagram below represents four rock samples.
  Which rock was formed by rapid cooling in a
  volcanic lava flow?
• 2- too fast- crystals
• Wont last!

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DO NOW
Which rock sample can be classified as a rock
with interlocking crystals.
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DO NOW

• Basalt (E) is a dark colored crystalline rock
  that formed when magma cooled and solidified
  slowly under the surface of the earth.
• Rock B is classified as an
• 1. Extrusive igneous rock with a coarse texture
  and felsic composition
• 2. Intrusive igneous rock with a fine texture and
  mafic composition
• 3. Intrusive igneous rock with a course texture
  and felsic composition
• 4. Intrusive igneous rock with a fine texture and
  mafic composition.

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