Rocks

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Rocks
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Types of Rocks

• There are three main types of rocks
• Igneous - formed when molten rock cools.
• Sedimentary formed by the cementing together
  of small grains of sediment.
• Metamorphic rocks changed by the effect of heat
  and pressure.

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Igneous Rocks
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Igneous Rock Types

• There are two types of igneous rocks
• Extrusive- igneous rocks that form on the surface
• Intrusive- igneous rocks that form under the
  surface

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Igneous Rocks

• These are rocks formed by the cooling of molten
  rock (magma.)

Magma cools and solidifies forming igneous rocks
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Rate of Cooling

• The rate magma cools will determine the size of
  the crystals
• Igneous rocks that cool slowly will form very
  large crystals
• Igneous rocks that cool rapidly will form very
  small crystals

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Texture

• Texture describes the overall appearance of
  igneous rocks based on the size and arrangement
  of crystals
• Fine grained texture
• Course gained texture
• Glassy texture

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Sedimentary Rocks
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Sedimentary Rocks

• Sedimentary rocks are compacted sediments
• Sedimentary rocks make up about 5 percent of the
  rocks on Earths crust

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Sedimentary Rocks roll in History

• Fossils are found in sedimentary rocks
• 75 percent of rock on the continents are
  sedimentary
• From sedimentary rocks geologist can reconstruct
  details of Earths history

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Sedimentary Rocks

• Sedimentary Rocks are rocks formed when particles
  of sediment build up and are cemented together
  by the effect of pressure and minerals.

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Metamorphic Rocks
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Metamorphic Rocks

• Metamorphic rocks are formed by the effect of
  heat and pressure on existing rocks.
• This can greatly affect the hardness, texture or
  layer patterns of the rocks.

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Rock Cycle