Rocks

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Rocks
ROCKS

• Chapter 10

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Rocks

• Naturally occurring solid material made of one or
  more minerals
• Grouped into 3 main types, based on the way it
  was formed

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IGNEOUS ROCKS
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IGNEOUS ROCKS

• Formed from magma that cools and hardens
• Fire Formed

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IGNEOUS ROCKS 2 types

• Intrusive rocks
• formed deep within Earth
• Cools slowly, large crystals
• Coarse grained

• Extrusive rocks
• formed from lava at Earths surface
• Cools quickly, small crystals
• fine grained

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IGNEOUS ROCKS texture

• Size of crystal grains and chemical composition
  are used to classify igneous rocks
• Texture depends on time it takes a rock to harden
  (cooling rate)

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IGNEOUS ROCKS porphyry(POR-fuh-ree)

• Igneous rock with a mixture of large and small
  crystals

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Two types of magma

• Felsic
• Light-colored
• Thick and slow flowing
• Rich in silica

• Mafic
• Dark-colored
• Very fluid
• Rich in iron

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Scoria
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Igneous Rock Structures

• Intrusions underground rock masses

• Extrusions surface rock masses

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INTRUSIONS

• Batholiths
• largest igneous intrusions
• Form when huge bodies of magma cool underground
• Cover 1000 km

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Batholith
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INTRUSIONS

• Laccoliths
• Domelike masses formed from magma bulging upward

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This laccolith in Red and White Mountain,
Colorado, is of Tertiary age. Overlying layers
of rock have been eroded.
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INTRUSIONS

• Dike
• Sheets of igneous rocks that cut across the rock
  layer

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Dike
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Dike
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INTRUSIONS

• Sill
• Sheet of hardened magma that forms between and
  parallel to layers of rock

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Sill
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EXTRUSIONS

• Volcanic neck
• The plug of hardened magma left in the vent from
  which lava flowed

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Volcanic neck
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INTRUSIONS

• Stock
• Similar to batholiths but less than 100 km

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SEDIMENTARY ROCKS
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Sedimentary Rocks

• 75 of Earths surface is sedimentary rock!

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How Sedimentary Rocks are made

• Mud, sand, gravel and shells are sediments that
  make up rocks
• Sediments are moved by wind and water
• Compaction Pressure placed in sediment layers
  cause them to change to rocks
• Cementation sediments are joined together
  (cemented) by minerals dissolved in water
• This process results in the formation of layers
  called strata.

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The major characteristics of all sedimentary
rocks is that they form layers!
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• "For your information, there's a lot more to
  ogres than people think...

Ogres are like sedimentary rocks!
Sedimentary rocks have layers...
Ogres have layers!
...We both have layers."
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Sedimentary rocks usually form in water

• Ripple marks and mud cracks

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Fossils often preserved in sedimentary rocks
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Sedimentary Rocks Classified by

• Composition
• Texture
• Grain size

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Types

• Clastic
• Organic
• Chemical

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1. Clastic Rocks

• Formed by broken pieces or fragments of rock
• Classified according to size and shape of
  fragments

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Clastic Rocks

• Conglomerates
• Made of rounded pebbles and other rocks of
  different sizes and cemented together by clay,
  mud ,or sand
• Formed when rivers deposit large pieces of rock
• Pieces of rock rounded by water before deposited

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Conglomerate
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Clastic Rocks

• Breccia
• Similar to conglomerates, but fragments are sharp
  and angular
• Not carried far enough by water to round the edges

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Breccia
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Clastic Rocks

• Sandstone
• Made of small, sand-sized grains
• Very common
• Resistant to wear and decay
• Used to make buildings

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Sandstone
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Clastic Rocks

• Mudrock
• Formed from small particles of clay
• Example shale

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shale
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shale
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2. Organic Rock

• Formed directly or indirectly from material that
  used to be living

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Organic Rock

• Fossilized Limestone
• Shells from dead animals (containing calcium
  carbonate) that sink to bottom of ocean floor

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Limestone
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Organic Rock

• Chalk
• Composed of animals and calcium carbonate that
  have been pressed together

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Chalk
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Organic Rock

• Coal
• Rock formed from plants that lived millions of
  years ago

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3. Chemical Rock

• Formed by chemical means that do not involve any
  living organisms
• Can occur through evaporation or chemical action

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Chemical Rock

• Limestone
• Formed directly from ocean water instead of
  organisms

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Chemical Limestone
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Chemical Rock

• Rock salt
• Natural form of common table salt
• Ex Halite

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Chemical Rock

• Rock gypsum

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METAMORPHIC ROCKS
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Metamorphic Rocks

• Metamorphism
• Changing of one type of rock in to another due to
  -
• Tremendous heat
• Great pressure
• Chemical reactions ( a change in composition of
  minerals)

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Metamorphic Rocks

• Types of Metamorphism
• Contact Metamorphism
• Occurs when rocks are heated by contact with
  magma or lava
• Covers a small area
• Regional Metamorphism
• Occurs when rocks are buried deep beneath Earths
  surface and changed by increase in temperature
  and pressure
• Covers a large area

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Types of Metamorphic Rock

• Foliated Texture
• Mineral crystals arranged in parallel layers or
  bands (flatten under pressure)

Slate
Schist
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Gneiss
(from clay or shale)
(from granite, basalt, or slate)
(from granite)
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You will need Quick-time to See the granite to
gneiss animation
http//geowww.ou.edu/jahern/dynamic/notes/met_rx/
AN07_001.MOV
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Foliated Texture
slate
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Foliated Texture
phyllite
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Foliated Texture
gneiss
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Types of Metamorphic Rock

• 2. Unfoliated Texture
• No bands of crystals
• Dont break in layers

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Unfoliated Texture
marble
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Unfoliated Texture
quartzite
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