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Igneous Rocks

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Igneous Rocks Hot rocks/Fire Rocks Igneous comes from Latin and means fire . Key Questions What is an Igneous Rock? How are Igneous Rocks classified? – PowerPoint PPT presentation

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Title: Igneous Rocks


1
Igneous Rocks
  • Hot rocks/Fire Rocks
  • Igneous comes from Latin and means fire.

2
Key Questions
  1. What is an Igneous Rock?
  2. How are Igneous Rocks classified?
  3. What are the two types of Igneous rocks?
  4. What are the characteristics of Intrusive Igneous
    Rocks?
  5. What are the characteristics of Extrusive Igneous
    Rocks?
  6. What is Volcanic Glass?

3
Igneous Rock
  • Igneous rocks form when molten rock cools and
    solidifies.
  • Molten rock is called magma when it is below the
    Earths surface and lava when it is above.

4
when molten rock cools and solidifies
Magma (below)
Lava (above)
5
Igneous Rock classification
  • Igneous rocks are classified two different ways
  • Where they were formed
  • What they are made from (mineral composition)

6
Intrusive Igneous Rocks
  • Igneous rocks that form below the Earths surface
    are called intrusive igneous rocks.
  • They form when magma enters a pocket or chamber
    underground that is relatively cool and
    solidifies into crystals as it cools very slowly.

7
Crystal size
magma
Intrusive
slowly
Magma (below)
when molten rock cools and solidifies
large
Lava (above)
8
Intrusive Igneous Rock
  • Most intrusive rocks have large, well formed
    crystals. The mineral crystals within them are
    large enough to see without a microscope.
  • The more slowly molten rock cools within the
    Earth, the larger the igneous rocks crystals will
    be.
  • Examples of intrusive igneous rocks are granite,
    gabbro and diorite

Diorite
9
Crystal size
magma
Intrusive
slowly
Magma (below)
when molten rock cools and solidifies
large
Lava (above)
Granite, gabbro, diorite
10
Extrusive Igneous Rocks
  • Extrusive igneous rocks, or volcanics, form when
    magma makes its way to Earth's surface. The
    molten rock erupts or flows above the surface as
    lava, and then cools forming rock.
  • Most extrusive (volcanic) rocks have small
    crystals. Examples include basalt, rhyolite, and
    andesite.

11
Lava
Crystal size
Quickly
Small or not visible
Extrusive
Pumice, obsidian, basalt
magma
Intrusive
slowly
Magma (below)
when molten rock cools and solidifies
large
Lava (above)
Granite, gabbro, diorite
12
Volcanic Glass
  • Pumice, obsidian, and scoria are examples of
    volcanic glass.
  • These rocks cooled so quickly that few or no
    mineral grains formed.
  • Most of the atoms in these rocks are not arranged
    in orderly patterns, and few crystals are
    present.

13
Glassy Igneous Rocks
Glassy Igneous Rocks cool so rapidly, that atoms
dont have enough time to get together, bond and
form crystals. To cool this quickly the rocks
MUST be extrusive.
  • Pumice (left)
  • Scoria (bottom left)
  • Obsidian (bottom)
  • Note gasses in the lava can cause fine holes
    called vesicles as seen in the pumice and scoria.

14
Classification
  • Igneous Rocks are also classified by their
    physical and chemical properties.

15
Lava
Crystal size
Quickly
Small or not visible
Physical chemical properties
Pumice, obsidian, basalt
Extrusive
magma
Intrusive
slowly
Magma (below)
when molten rock cools and solidifies
large
Lava (above)
Granite, gabbro, diorite
16
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