Chapter 3 Rocks

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Chapter 3 Rocks

• Why study rocks?
• - rocks tell the story of your location
• EX Indiana is made of mostly limestone
  formed in a shallow marine setting so in the
  past Indiana was under water
• How is a rock different than a mineral?
• Rock a naturally occurring combination of
  minerals
• ? Rock will show some of the properties of the
  minerals that make it up
• EX Limestone is made of mainly calcite so it
  reacts to acid

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3 Types of Rocks

• Igneous rock made from cooled magma either
  above or below ground
• EX Granite
• Sedimentary rock formed from compacted
  cemented sediments
• EX Limestone
• Metamorphic a rock that has been changed
  (cooked) by increasing temperature and/or
  pressure to form a new rock
  EX Marble

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Rocks are continually changing from one type to
another Rock Cycle
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Igneous Rocks

• Formed from cooled magma
• Can form at 2 locations
• 1. Below Ground Intrusive
• - slow cooling of magma because ground is
  insulating this allows grains/crystals to
  grow large
• ? Coarse Grained Texture
• 2. Above Ground Extrusive
• - quick cooling no time for crystals to
  grow so extrusive igneous rocks have small
  grains
• ? Fine Grained Texture

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Igneous Rock Fine Grained Texture Cont

• - HOWEVER..Exceptionally quick cooling above
  ground can give special textures
• A. Glassy lava instantly cooled by
  seawater No grains in rock
• ? Very smooth/glassy feel
• EX Obsidian
• B. Pyroclastic Texture magma cooled instantly
  by being shot into the air (i.e. volcano)
• ? rock has air pockets and very rough feel
• EX Pumice Scoria

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How do you classify Igneous Rocks?

• Texture Coarse, Fine, Glassy, Pyroclastic
• Mineral Composition color of rock
• A. Light white, clear, light pink, light gray
• B. Intermediate equal parts black white
  (salt pepper) or dark pinks and dark grays
• C. Dark Black

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Igneous Rock Identification Chart
MINERAL COMPOSITION MINERAL COMPOSITION MINERAL COMPOSITION
Dark Intermediate Light
TEXTURES Coarse Gabbro Diorite Granite
TEXTURES Fine Basalt Andesite Rhyolite
TEXTURES Glassy Obsidian Obsidian ----------
TEXTURES Pyroclastic Scoria Scoria Pumice
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Sedimentary Rocks

• Formed from compacted/cemented sediments
• Weathering process that breaks down rocks into
  sediments
• Compaction process that squeezes or compacts
  sediments
• Cementation process where smaller dissolved
  minerals are deposited between sediments/rocks
  glues pieces together

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• 2 Types of Sedimentary Rocks
• 1. Clastic made of weathered broken
  pieces of rock
• 2. Chemical form when
• dissolved minerals precipitate (separate) from
  water
• EX lake totally dries up during the summer

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How are Sedimentary Rocks classified?

• Type Clastic vs. Chemical
• Texture grain size (coarse ? fine)
• Composition minerals
• (chemical sed. rocks only)

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Sedimentary Rock Identification Charts
Clastic Sedimentary Rocks Clastic Sedimentary Rocks Clastic Sedimentary Rocks
Texture Rock Name
Coarse/Gravel Conglomerate
Medium/Sand Sandstone
Fine/Mud Shale

Chemical Sedimentary Rocks Chemical Sedimentary Rocks Chemical Sedimentary Rocks
Composition Texture Rock Name
Calcite Very Coarse Coquina
Calcite Coarse Fossiliferous Limestone
Calcite Medium Limestone
Gypsum Fine Rock Gypsum
Halite Fine Rock Salt
Organic Matter Medium/Fine Coal
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Metamorphic Rocks

• Form when pre-existing rocks are changed by heat
  and/or pressure
• Occurs during mountain building, volcanic
  activity, etc

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• 2 types of Metamorphic Rocks
• 1. Contact when magma forces its way into
  cracks/ layers of rock
• - Rise in Temperature only
• - Small changes to surrounding rocks
• 2. Regional occurs during large scale mountain
  building
• (EX 2 continental plates colliding)
• - Extreme rise in Temperature Pressure
• - Large changes to surrounding rock
• - Rock usually becomes layered

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How are Metamorphic Rocks classified?

• Composition of parent material
• Texture layered vs. non-layered
• The longer a rock is metamorphosed, the more
  layered its appearance (i.e. the longer it has
  been cooked, the more obvious layers it
  has)

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Metamorphic Rock Identification Chart
Parent Rock Texture Rock Name
Shale Very Fine Layers Slate
Slate Fine Layers Phyllite
Phyllite Medium Layers Schist
Schist Coarse Layers Gneiss

Limestone NO Layers Marble
Sandstone NO Layers Quartzite
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Ch. 3 Final AssignmentWorth 25 points !

• Pg. 89-90
• 1, 2, 4, 5, 8 write out questions and answers
• 14, 17, 19, 21, 22 write out answers only, in
  complete sentences
• Vocabulary Words
• Cementation Metamorphic Rock
• Chemical Sed. Rock Pyroclastic
• Clastic Sed. Rock Regional Met.
• Compaction Rock
• Contact Met. Rock Cycle
• Extrusive Sedimentary Rock
• Igneous Rock Weathering
• Intrusive

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SS 8

• Put the date and SS 8 on your paper.
• Copy the question answer it.
• What is the Rock Cycle?