Rocks

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Rocks
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Whats a Rock?

• A solid chunk of one or more minerals (or
  sometimes mineral-like matter)

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The Rock Cycle
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A Quick Quiz

• The type of rock that starts it all!
• IGNEOUS!
• A rock formed by squeezing and heating.
• METAMORPHIC
• A rock formed from smaller rocks and material
  being compacted together.
• SEDIMENTARY

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More Questions!

• A rock formed from cooling magma or lava
• IGNEOUS
• A sedimentary rock might have originally been one
  of this(these) kind of rock(s)
• IGNEOUS, METAMORPHIC, or SEDIMENTARY
• A metamorphic rock might have originally been one
  of this(these) kind of rock(s)
• IGNEOUS or SEDIMENTARY

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Rocks, Part 2

• Igneous Rocks

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Igneous

• From Latin ignis FIRE!
• Formed when lava or magma cools and hardens

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Examples of Igneous Rocks
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Several Ways to Classify Igneous Rocks

1. Intrusive vs. Extrusive
2. Texture
3. Composition

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2. Texture

1. Coarse Grain Texture
2. Fine Grain Texture
3. Glassy Texture

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Coarse Grain Texture

• Relatively Large Crystals
• Formed by slow cooling of magma in Earth

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Fine Grain texture

• Smaller Crystals
• Formed by rapid cooling of magma or lava

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Glassy Texture

• Crystals so tiny the rock looks like glass
• Formed by extremely fast cooling of lava

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3. Composition

1. Granitic Composition
2. Basaltic Composition

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Granitic Composition

• Lots of light-colored silicates, esp. quartz and
  feldspar
• Usually speckled with about 10 dark silicates
• Make up most of continental crust

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Basaltic Composition

• Mainly dark silicates
• Darker and denser than granite
• Make up most of ocean floor (formed at ocean
  ridges)

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Rocks, Part 3

• Sedimentary Rocks

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Sedimentary

• From Latin sedimentum settling
• Formed when sediments are compacted and cemented
  together

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Create a Sedimentary Rock in Only 3 Steps!

• Step 1 Weather/erode parent rock and deposit
  sediment.
• Step 2 Compact sediment.
• Step 3 Cement sediment.
• Voila! Your sedimentary rock is complete.

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Step 1 Weather/erode parent rock and deposit
sediment.
Table Mountain, South Africa
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Step 2 Compact sediment.

• As sediments are buried, the increasing weight of
  sediments above them squishes them together and
  removes most water.

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Step 3 Cementation.

• Finally, dissolved minerals are deposited in the
  spaces between the sediments. The minerals
  solidify and cement the particles together (like
  mortar).

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Examples of Sedimentary Rocks
Rounded, Gravel-sized Sediment
Conglomerate
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Another Example
Angular Gravel-sized Sediment
Breccia
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And Another
Sand-sized Sediment Grains
Sandstone
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Sandstone in Architecture
The Treasury Petra, Jordan
And Its Still Used Today!
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And Another Example
Fine-grained Sediment
Shale
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More Sedimentary Rocks
Siltstone
Chalk
Limestone
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A Special Word About Limestone

• Very common
• Main mineral Calcite (CaCO3)
• Often used as building material
• Often formed from marine organisms

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Indiana Limestone in Buildings
AND 35 of 50 Statehouses made of Indiana
Limestone!
National Holocaust Museum
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Why Studying Sedimentary Rocks is Useful

• Formed by adding successive layers
• Contents of layers tell a story of that time
• Fossils of organisms, floods, volcanoes,
  earthquakes, climate

Limestone from Indiana???
A Trilobite Fossil
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Rocks, Part 4

• Metamorphic Rocks

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Metamorphic

• To change form due to heat and pressure
• Formed from either igneous or sedimentary rocks

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The Role of Heat

• Provides energy to drive reactions between
  minerals
• Existing minerals may be re-crystallized into a
  different form or new minerals may be formed
• Source of heat
• Contact with magma itself
• Increasing depth (temperature increases 20-30oC
  per kilometer)

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Role of Pressure

• Farther down a rock is buried, the greater the
  pressure
• Increased pressure smooshes minerals together or
  causes them to re-crystallize
• Under high temp and pressure, rocks flow
  instead of fracturing

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Foliated vs. Nonfoliated Metamorphic Rocks

• Foliated striped

• Nonfoliated not striped

Gneiss
Marble
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More Metamorphic Rocks
Slate
Shale
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Another Meta
Gneiss
Granite
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And Another
Marble
Limestone
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One More
Quartzite
Sandstone
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And Lastly

• Hornfels
• No specific composition
• Was baked by magma in contact the parent rock