Types of Rocks:

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Types of Rocks

1. Igneous
2. Sedimentary
3. Metamorphic

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Igneous Rocks

• Rocks that forms when magma cools and hardens.
• Form by solidification (crystallization) of
  melted minerals.

• At the surface, LAVA hardens to form EXTRUSIVE
• rocks with tiny (FINE-GRAINED) crystals or GLASSY
  
• (no crystal) textures.

• Beneath the surface, MAGMA hardens to form
• INTRUSIVE rocks with easily visible
  (COARSE-GRAINED) crystal texture.

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2 groups of Igneous Rock

• Intrusive igneous rock The slow cooling of
  magma deep below the crust.
• Slow loss of heat ? Long time ? large, well
  developed crystal grains.
• Extrusive igneous rock The rapid cooling of
  lava on the earths surface.
• Fast loss of heat ? Short time ? Cant form
  large crystals

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Granite
Rhyolite
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Mineral Composition

• Felsic igneous rocks rich in light-colored
  minerals such as orthoclase and quartz

• Mafic igneous rocks rich in dark-colored
• ferromagnesian minerals

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Igneous Examples

• Dark-colored, fine- grained, extrusive
• Formed where lava erupted onto surface
• Most widespread igneous rock

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Igneous Examples

• Natural volcanic glass
• Forms when lava cools very quickly
• Usually dark, but small pieces may be clear
• Fractures along curved (conchoidal) surface

Obsidian

• Light colored, frothy
• (many air spaces)

Pumice
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Sedimentary Rocks

• Formed from the compaction and cementation of
  loose, solid particles (aka sediment).

• Types of Formation
• Lithification of sediment
• Precipitation from solution
• Consolidation of organic remains

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Types of Formation
CEMENTATION
COMPACTION
Lithification
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Types of Formation
Precipitation
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Sedimentary Rock Groups

• CLASTIC
• Comprised of
• cemented sediment
• CHEMICAL
• Precipitation of
• minerals from
• solution
• ORGANIC
• From the remains
• of organisms

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Sedimentary Examples
Conglomerate
Breccia
Rounded
Angular
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Sedimentary Examples

• Coquina
• Type of limestone made up of fossil shells with
  little or no matrix

Fossiliferous Limestone Contains the remains of
ancient plants animals, known as fossils
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Metamorphic Rocks

• Formed when existing rocks undergo great amounts
  of heat pressure.
• Minerals recrystallize to form new minerals
• Minerals change in size shape
• Minerals may line up in parallel bands
• All of this creates a new rock!

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Controlling Factors of Metamorphism

• Parent Rock composition
• Temperature certain minerals are unstable under
  specific temperatures
• Time the longer it takes for metamorphism to
  occur, the more change that occurs
• Pressure increases as depth into the Earths
  crust increases

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Types of Metamorphism

• Contact Metamorphism
• magma comes into contact with existing rock
• heat from the magma can change the structure
  mineral makeup of that rock.

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Types of Metamorphism

• Regional Metamorphism
• occurs over a large area
• changes that take place at great depth (more than
  5km) below ground
• related to plate tectonics
• causes a change in texture, structure, or
  composition of a rock.

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Regional Metamorphism
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Metamorphic Rock Groups

• Foliated minerals within the rock arranged in
  bands or planes
• Banding- alternating bands of light and
  dark minerals
• Schistocity- minerals have grown parallel
  planes in rock
• Rock Cleavage- looks like a rock can
  break into plates

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Foliation
Realigned minerals in bands
Minerals in random order
HEAT
HEAT
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Foliated Metamorphic Rocks
Banding
Schistocity
Rock Cleavage
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Identifying Rocks

• Observe and ask questions
• What does the rock look like?
• Examine the grain of a section.
• What is the rock's composition?
• Determine what minerals are in it.
• Where was the rock found?
• Mountain
• Stream or river
• Volcano
• Ocean floor