Classifying Rocks

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Classifying Rocks

• Rocks are made of minerals and other materials

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Ways to determine composition

• Color
• Texture
• Mineral Composition

3
Texture

• The appearance (look feel)
• Grain size
• large crystals coarse grained
• small crystals fine grained

4
Texture

• Grain shape
• Smooth
• Jagged
• Grain pattern
• Banded
• Non-banded
• No visible grain

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Origin of Rocks

• Igneous Cooling of MOLTEN rock (below or above
  surface)
• Sedimentary Compaction and cementation of
  minerals and plant/animal remains
• Metamorphic Exposed to heat, pressure, /or
  chemical reactions.

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Compare and Contrast

• How are Igneous, Sedimentary, and Metamorphic
  rock alike different.

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Igneous Rock

• Classified by 3 characteristics.

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Igneous Rock

• Origin
• Texture
• Mineral Composition

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Origin

• Where rock was formed
• Extrusive formed from lava on the surface. Ex
  (basalt) small crystals
• Intrusive - formed from hardened magma. Ex
  (granite) large crystals

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Texture

• The size and shape of mineral crystals.
• Fine grained fast cooling small
• Coarse grained slow cooling large
• Glassy
• Porphyritic large small crystals. (2 stages
  of cooling)

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Compare and Contrast

• How are Basalt and Granite similar.
• How are Basalt and Granite different.

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Mineral Composition

• Low silica dark color (basalt)
• High silica light color (granite)

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Sedimentary Rocks

• Particles deposited by water, wind, and ice.

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Transforming Sediment to Rock

• Erosion
• Deposition
• Compaction
• Cementation

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Sedimentary Rock

• Erosion
• H2O or wind loosen and remove fragments of rock
• Deposition
• Sediment settles out of H2O or wind

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Sedimentary Rock

• Compaction
• Process that presses sediment together
• Cementation
• Process which dissolved minerals crystallize
  and glue particles of sediment together.

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Types of Sedimentary Rock

• Clastic
• Organic
• Chemical

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Clastic

• Rock fragments squeezed together
• Shale formed from clay, smooth feel/easily
  splits.
• Sandstone compaction/cementation of sand
• Conglomerate/Breccia Various size grains.
  Conglomerate round Breccia sharp

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Compare and Contrast

• Compare and contrast shale and sandstone.
  Include what they are made of and how they form.

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Organic

• Formed where the remains of plants and animals
  are deposited in thick layers
• Ex Coal compaction of swamp plants in water.
• Ex Limestone hard shells ? calcite ? chalk

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Chemical

• Formed when minerals dissolved in a solution
  crystallize.
• Or
• Mineral deposits left when seas or lakes
  evaporate.
• Ex Gypsum Halite

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Coral Reefs

• Form in warm shallow water
• 3 types
• Fringing close to shore. Separated by shallow
  water.
• Barrier about 10 km from land
• Atoll Ring shaped, far from land.

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Metamorphic Rock

• Changing form
• Heat and pressure beneath Earths surface change
  rocks.

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Classifying Metamorphic Rocks

• Arrangement of grains that make up the rock.
• 2 Basis forms
• Foliated parallel layers or bands
• Ex slate, schist, and gneiss.
• Non-foliated random arrangement
• Ex Quartzite and marble

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Critical Thinking

• Why are you less likely to find fossils in
  metamorphic rocks than in sedimentary rock?

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The Rock Cycle
http//www.classzone.com/books/earth_science/terc/
content/investigations/es0602/es0602page02.cfm

• A series of processes on the surface and inside
  Earth that slowly changes rock from one kind to
  another

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The Rock Cycle
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2 Types of Plate Movement

• Subduction of oceanic plates
• Colliding continental plates

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Critical Thinking

• Begin with a grain of sand on a beach. Describe
  what happens as you follow the grain through the
  rock cycle until it returns to a beach as a grain
  of sand again.