Igneous%20Rocks

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Igneous Rocks
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Whats behind Mt. Rushmore
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Igneous Rocks
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Magma vs. Lava

• Magma
• Molten (melted) rock
• Gases
• Mineral crystals
• Beneath the surface
• Lava
• Magma on the surface

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Composition of Magma

• Elements
• O, Si, Al, Fe, Mg, Ca, K, Na
• Compounds
• SiO2 - Silica
• Most abundant
• Greatest effect on magma characteristics

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Composition of Magma

• Basaltic Magma
• 50 Silica
• Oceanic Lithosphere
• Andesitic Magma
• 60 Silica
• Granitic Magma
• 70 Silica
• Continental Lithosphere

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Mineral Composition

• Felsic
• Form from granitic magma
• Continental Lithosphere
• Light-colored
• Gray, white, pink
• High silica content
• Low iron and magnesium

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Mineral Composition (cont.)

• Intermediate
• Forms from andesitic magma
• Dark Light-colored
• 50/50
• Half black/half white
• Moderate levels of silica content and iron and
  magnesium
• DOES NOT HAVE
• K-SPAR
• No pink

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Mineral Composition (cont.)

• Mafic
• Forms from basaltic magma
• Oceanic Lithosphere
• Dark-colored
• Black/dark green
• Low silica content
• High iron and magnesium

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Environment of Formation

• Intrusive
• Magma inside the earth
• Cools slowly
• Large crystals
• Extrusive
• Lava on surface
• Cools quickly
• Small crystals (if any)

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Texture

• Glassy
• Non-crystalline
• Fine
• Less than 1 mm
• Coarse
• 1mm to 10 mm
• Very Coarse
• 10 mm or larger

Extrusive

Intrusive
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Texture (cont.)

• Vesicular
• Has gas pockets
• Non-vesicular
• No gas pockets

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Some Igneous Rocks Are Named on Textural Criteria

• Pegmatite Extremely large crystals
• Pumice - Porous
• Obsidian - Glass
• Tuff - Cemented Ash

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Porphyritic Texture

• Large well-formed crystals surrounded by small
  finer-grained crystals
• Complex cooling history
• Cools slowly
• Creating large crystals
• Then cools very fast
• Creating small crystals

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Granite The Wisconsin State Rock
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Obsidian
Vesicular Scoria Basalt
(red)
Felsic Inter Mafic
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Sedimentary Rocks
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Origin of Sedimentary Rocks

• Erosion
• Creating of sediments
• Physical and chemical weathering
• Transportation
• Sediments are brought together

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Origin of Sedimentary Rocks

• Deposition
• Water deposition commonly forms layers
• Sorting
• Glaciers and landslides do not create layers
• Burial
• To create heat and pressure
• Lithification
• Cementing (gluing) together of sediments
• Making sedimentary rocks

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Sedimentary Structures

• Bedding Layers of Rock
• Graded Bedding largest on the bottom and
  smallest particles on the top

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Sedimentary Structures

• Bedding Layers of Rock
• Horizontal Bedding
• Layers deposited horizontally

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Sedimentary Structures

• Bedding Layers of Rock
• Cross Bedding
• Layers at angles

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Sedimentary Structures

• Ripple Marks
• Symmetrical
• Beach
• Water
• movement in
• two directions

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Sedimentary Structures

• Ripple Marks
• Asymmetrical
• Stream
• Water
• movement in
• one direction

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Not this One Direction
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Types of Sedimentary Rocks

• Clastic
• Sediments glued together
• Clastic pieces Greek
• Chemical
• Precipitation of dissolved minerals in water
• Organic
• Accumulation of remains of once living things

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Clastic Sedimentary Rocks

• Coarse-Grained Clastics
• Gravel sized particles
• Transported by high energy flows
• Conglomerates
• Gravel-sized rounded particles
• Transported great distances
• Breccias
• Gravel-sized angular particles
• Transported short distances

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Clastic Sedimentary Rocks

• Conglomerate

• Breccia

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Clastic Sedimentary Rocks

• Medium-Grained Clastics
• Sand sized particles
• High Porosity
• of open space
• Can contain fluids
• Groundwater, air, natural gas, and oil

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Clastic Sedimentary Rocks

• Fine-Grained Clastics
• Siltstone
• Shale
• Low porosity
• Particles are too small

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Chemical Sedimentary Rocks

• Minerals dissolve during chemical weathering
• Carried to lakes and oceans
• Water evaporates, minerals are supersaturated,
  and precipitate out
• Called evaporites
• Calcite, halite, and gypsum

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Organic Sedimentary Rocks

• Limestone
• Calcite from sea organisms shells
• Reacts with acid
• Coal
• Lithification of plant remains

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Organic Sedimentary Rocks

• Limestone

• Coal

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Sedimentary Rock Identification
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Metamorphic Rocks
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Metamorphic Rocks

• Metamorphism
• The mineralogical, chemical, and structural
  adjustment of solid rocks to the physical and
  chemical conditions imposed at a depth below the
  surface zones of weathering and cementation,
  which differ from the conditions under which the
  rocks were originated.
• Sedimentary and igneous rocks are changed due to
  pressure and heat or chemical reactions while
  remaining solid.

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Causes of Metamorphism

• Temperature
• Earths internal heat
• Igneous Intrusion
• Pressure
• Increases with depth
• Vertical pressure from weight of overlaying rocks
• Mountain Building
• Horizontal pressure form colliding plates.
• Chemistry
• Fluids flowing through the rocks react, forming
  new minerals

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Causes of Metamorphism

• Rocks change form while remaining solid
• If rock melts, it becomes
• Magma, which will then produce
• Igneous Rocks.
• Metamorphism ends when a rock melts

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Metamorphic Rocks
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Metamorphic Textures

• Foliated
• Have a banded appearance because the minerals in
  the rock are in parallel alignment
• An animation of metamorphic rocks forming

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Grades of Metamorphism
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Metamorphic Textures

• Foliated

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Metamorphic Textures

• Nonfoliated
• No banding
• Interlocking mineral grains
• THE MARSHMALLOW EFFECT

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Metamorphic Textures

• Nonfoliated Foliated

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Metamorphic Rocks
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Grades of Metamorphism

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Metamorphic Rocks
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Igneous Sedimentary Metamorphic




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Igneous Sedimentary Metamorphic
Crystals Cooling rate Sediments Gravel, sand, silt/clay Foliated Bands
Mineral Composition Felsic, Intermediate, Mafic Fossils Foliated Bands
Glassy Layers Nonfoliated Crystals smooshed together Marshmallow Effect
Vesicular Some react with acid Nonfoliated Crystals smooshed together Marshmallow Effect
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The Rock Cycle

• The circular process by which each of the three
  major rock types is formed from the others

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The Rock Cycle
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The Rock Cycle
Granite Sandstone Quartzite
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What Rocks Tell Us
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Rock Type How Classified How Classified What They Tell Us What They Tell Us
Igneous Composition   Felsic Light   Continental Lithosphere
Igneous Composition   Intermediate 50/50 Tectonic Setting Boundary Between
Igneous Composition   Mafic Dark   Oceanic Lithosphere
Igneous Texture   Intrusive Magma Cooling Slowly DEEP
Igneous Texture   Extrusive Lava History Quickly Surface Volcanic
Sedimentary Composition Clastic (Pieces)   Erosion Sedimentary Structures
Sedimentary Composition Chemical (PPT) Surface Environment Water
Sedimentary Composition Organic (Fossils)   Life Forms Present
Sedimentary Grain Size/Shape Large   High
Sedimentary Grain Size/Shape Small Energy of Low
Sedimentary Grain Size/Shape Rounded Environment High
Sedimentary Grain Size/Shape Angular   Low
Metamorphic Composition Quartzite   Sandstone
Metamorphic Composition Marble Original Rock Type Limestone
Metamorphic Composition Slate   Shale
Metamorphic Texture Foliated Degree of Low to High
Metamorphic Texture Nonfoliated Change Low