The Rock Cycle

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The Rock Cycle

• An Interactive Presentation by
• Andrew DeWitt

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The Rock Cycle Home Page

• Overview of Rock Cycle
• Igneous Rocks
• Sedimentary Rocks
• Metamorphic Rocks
• Resources
• Concept Map

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Overview of the Rock Cycle

• The rock cycle describes Earths natural process
  of recycling rocks and sediments. All the rocks
  on Earth fall into the three distinct categories
  of sedimentary, igneous, or metamorphic rocks.
  The names of these rock types refer to the way
  the rocks were formed.

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Igneous Rocks

• Igneous rocks are formed from magma, the molten
  form of Earths mantle layer. These rocks can
  form above ground when lava comes out of a
  volcano, or they may form under the Earths
  surface when magma cools. When igneous rocks are
  broken down chemically and physically the pieces
  of this rock may be lithified creating
  sedimentary rock. Or, if these rocks undergo
  heat and pressure they may turn into metamorphic
  rock.

Granite is a common igneous rock that is formed
under the Earths surface. About 75 of the
Earths crust is granite.
Click here for examples of igneous rocks
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Sedimentary Rocks

• Sedimentary rocks form from weathered pieces of
  other rocks (metamorphic, igneous, or other
  sedimentary rocks) or from weathered shells of
  sea creatures. Also, sedimentary rocks can be
  precipitated directly out of water as is the case
  with limestone. Coal is also an example of a
  sedimentary rock. Coal forms when dead organic
  matter is squeezed together before the material
  can be decayed. Whatever the case, these rocks
  must be squeezed and cemented together.

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Click here for examples of sedimentary rocks
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Metamorphic Rocks

• Metamorphic rocks form under intense heat and
  pressure. These rocks may start out as igneous,
  sedimentary or another type of metamorphic rock,
  but due to heat and pressure the characteristics
  change, generating a metamorphic rock. It is
  important to know that rocks continue to change
  form. What was once a sedimentary rock may
  become a metamorphic rock when subjected to
  extreme heat and pressure. With sufficient time
  and weathering, that metamorphic rock can become
  a sedimentary rock once again.

Evidence of deformation and stress is often
associated with metamorphic rocks due to the fact
that they were subject to extreme heat and
pressure.
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Click here for examples of metamorphic rocks
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Resources

• Photos from the following siteshttp//evolution.
  itgo.com/rock_cycle/cycle.htmlwww.rocksandmineral
  s4u.com/rock_cycle.htmlwww.geol.umd.edu/.../GEOL3
  88/lectures/02.htmlgeology.com/rocks/igneous-rock
  s.shtml
• Video from United Streaminghttp//streaming.disc
  overyeducation.com/index.cfm

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Examples of Igneous Rocks
Rocks formed as lava cooling on Earths surface
Rocks formed as magma cooling under the Earths
surface
Basalt
Gabbro
Diorite
Rhyolite
Obsidian
Granite
Click to go back to igneous rocks information
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Examples of Sedimentary Rocks
Click to go back to sedimentary rocks information
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Examples of Metamorphic Rocks
Increasing metamorphic grade (more heat and
pressure) from lower left to upper right.
Schist
Gneiss
Slate
Phyllite
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Click to go back to metamorphic rocks information
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Concept Map
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