EarthComm

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EarthComm

• Materials are or may be copyrighted. These
  should only be used for educational purposes
  (Fair Use Policy).

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In the Beginning . . .

• Universe began with the Big Bang
• Stars formed from hydrogen
• Stars fused hydrogen into different elements
• Stars exploded
• Some of the material came together to form our
  solar system and Earth

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Minerals

• Definition of a Mineral
• Naturally occurring
• Solid substance
• Orderly crystalline structure
• Definite chemical composition
• Generally considered inorganic (did not come from
  living things)
• Minerals have all 5 characteristics

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Minerals

• Formation of minerals
• Crystallization from magma (molten material)
• Precipitation formation of a solid in a
  solution during a chemical reaction
• Pressure and temperature from crushing rocks
• Hydrothermal solutions heated water containing
  dissolved substances deposit them to form minerals

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Minerals Formed as a Result of Crystallization of
Magma
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Minerals

• Can be classified based on their composition
• Silicates contain silicon and oxygen
• Others such as carbonates, oxides, sulfides,
  native elements, etc.

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The Silicon-Oxygen Tetrahedron
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Silicon-Oxygen Chains, Sheets, and
Three-Dimensional Networks
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Sulfides
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Native Copper
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The Rock Cycle

• Rocks are any solid mass of minerals
• 3 categories of Rocks
• Igneous
• Sedimentary
• Metamorphic

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The Rock Cycle

• Processes in the rock cycle
• Rock is melted to form magma. When it reaches
  the surface, it is called lava.
• Magma and lava cools to form igneous rocks.
• Surface rocks are eroded (broken down) by water,
  air, and living things during weathering to form
  sediments (soil) (see p. 79)

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Unloading and Exfoliation of Igneous Rocks
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Increase in Surface Area by Mechanical Weathering
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Mechanical Weathering Wedging
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Lichen
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Weathering and Biological Activity
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Chemical Weathering
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Spheroidal Weathering
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The Rock Cycle

• Processes in the rock cycle
• Sediment is compacted and cemented in water to
  form sedimentary rocks (see p. 79).
• Rock changed by heat and pressure is metamorphic
  rock.

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The Rock Cycle
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The Rock Cycle

• Causes of Rock Cycle
• Heat from inside Earth
• Energy from the sun powers weathering

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Igneous Rocks

• Igneous rocks form from cooling magma or lava
  (see p. 75).
• Have interlocking crystalline textures
• Coarse-grained texture is caused by slow cooling
• Fine-grained texture is caused by rapid cooling
• Glassy texture is caused by very rapid cooling.

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Course-Grained Igneous Texture
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Fine-Grained Igneous Texture
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Obsidian Exhibits a Glassy Texture
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Igneous Rocks

• Composition
• Granitic (granite) composition rocks are
  silica-rich and are mostly light-colored.
  Usually found in the upper crust (see p. 83).
• Basaltic (basalt) composition rocks are iron-rich
  and are mostly of dark-colored. Usually found in
  the lower crust (see p. 83).

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Basalt Igneous Rocks
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Porphyritic Igneous Texture
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Classification of Igneous Rocks
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Sedimentary Rocks

• Sedimentary rock is formed from the weathered
  sediment (see p. 75)
• Have fragmental textures
• Goes through the following processes
• Erosion the weathering and removal of rock.
• Deposition an agent of erosion (water, wind,
  ice, or gravity) drops sediments
• Compaction is a process that squeezes sediments
• Cementation takes place when dissolved minerals
  are deposited in the tiny spaces among the
  sediments

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Sedimentary Rocks

• Two main categories
• Clastic sedimentary rocks are composed of
  compacted sediment and are classified by particle
  size
• Chemical sedimentary rocks form when dissolved
  substances precipitate, or separate, from water
  (see p. 73).

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Shale with Plant Fossils
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Conglomerate
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Fossiliferous Limestone
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Classification of Sedimentary Rocks
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Metamorphic Rocks

• Metamorphic rock is formed by the changing of
  solid rock deep within Earth by heat, pressure,
  and/or solutions (see p. 75).
• Pressure and high temperature occur when plates
  collide (see p. 89)
• In hydrothermal solutions (see p. 73) hot water
  escape from magma which dissolves original
  minerals and then deposits new ones

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Origin of Pressure in Metamorphism
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Metamorphic Rocks

• Two main categories
• Foliated metamorphic rock has a banded or layered
  appearance
• Nonfoliated metamorphic rock does not have a
  banded texture

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Gneiss
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Marble
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Classification of Metamorphic Rocks
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Earths Layers

• Earths interior consists of three major zones
• Crust thin, rocky outer layer
• Continental plate
• Upper crust composed of granite (p. 77)
• Lower crust is more like basalt (p. 77)
• Oceanic plate
• Basaltic composition
• Younger than the continental crust

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Earths Layers

• Mantle located between crust and core
• Upper mantle is mostly igneous rock
• Lower mantle flows like a viscous (thick) liquid

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Earths Layers

• Core inner layer of Earth
• Composed of liquid iron and nickel
• Convective flow (see p. 87) of iron helps
  generate Earths magnetic field

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Earths Layers
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Earths Layers

• These layers are also referred to as the
• Lithosphere contains the crust and uppermost
  mantle
• Cool, rigid
• Asthenosphere located beneath the lithosphere
  contains the upper mantle
• Soft, hotter layer that is easily deformed

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Earths Layers
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Plate Tectonics

• Continental drift states that the continents had
  once been joined to form a single supercontinent,
  called Pangea
• Continental drift hypothesis supported the theory
  called plate tectonics.
• In plate tectonics theory, plates (rigid sections
  of the lithosphere) moves over the soft material
  of the asthenosphere (p. 83).

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Breakup of Pangaea
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Causes of Plate Motion

• Thermal convection currents (flow) in the mantle
  is the basic driving force for plate movement.
• Hot material (magma) rises, colder material
  sinks, circulating the mantle material

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Mantle Convection Models
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Three Types of Plate Boundaries
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Convergent Boundaries

• Convergent boundaries form where two plates
  collide.
• When a denser plate (usually oceanic) is forced
  down into the mantle beneath a lighter plate
  (usually continental), this creates a subduction
  zone, where lithosphere is destroyed.

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Convergent Boundaries

• 3 types
• Oceanic-Continental
• Denser oceanic plate collides and subducts
  underneath the continental plate (p. 83)
• Forms volcanoes and mountains
• Ex the Andes the Cascades.

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Oceanic-Continental Convergent Boundary
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Convergent Boundaries

• Oceanic-Oceanic
• Two oceanic plates (p. 83) converge and one
  descends beneath the other.
• Creates an ocean trench and volcanic islands
• Ex Aleutian islands Japan

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Oceanic-Oceanic Convergent Boundary
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Convergent Boundaries

• Continental-Continental
• When two continental plates (p. 83) collide
• Because both continental plates are lighter, they
  push up to form mountains
• Ex the Himalayas the Appalachians

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Continental-Continental Convergent Boundary
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Collision of India and Asia
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Divergent Boundaries

• Divergent boundaries are where two plates move
  apart.
• In this process, crust gets thinner, rift valleys
  form, which later forms into mid-ocean ridges
  (chain of volcanoes)
• Ex Mid-Atlantic Ridge, East Pacific Rise
• Seafloor spreading produces new oceanic
  lithosphere (p. 83).

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Spreading Center
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East African Rift Valley
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Breakup of Pangaea
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Mid-Atlantic Ridge
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Hydrothermal Vents
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Tube Worms Found Along Hydrothermal Vents
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Transform Boundaries

• At a transform fault boundary (parallel slip),
  plates grind past each other without destroying
  or producing the lithosphere (p. 83).
• Ex San Andreas Fault

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Transform Fault Boundary
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San Andreas Fault
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Evidence of Plate Tectonics Matching Plate
Features

• Earthquakes and volcanoes near plate edges
• The Continental puzzle
• Matching fossils, rock types and structures
• Ancient climates

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Earthquakes and Volcanoes
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Matching Mountain Ranges
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Breakup of Pangaea
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Glacier Evidence
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Evidence of Plate Tectonics Matching Plate
Features

• A hot spot is where a magma plume (stream of
  magma) rises to Earths surface, creating
  intraplate volcanoes
• Ex The Pacific plate moves over a hot spot,
  producing the Hawaiian Islands.

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Hot Spot
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Evidence of Plate Tectonics Features of the
Ocean Floor

• Rock age - the youngest oceanic crust is at the
  ocean ridge where magma forms new rock, and the
  oldest is at the continental margins as shown in
  seafloor spreading.

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Spreading Center
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Atlantic Continental Margin
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Evidence of Plate Tectonics Features of the
Ocean Floor

• Magnetic patterns in the ocean floor shows rock
  formed during times when the Earths magnetic
  field was normal and reversed.
• Polarity is the direction of the magnetic field
• Strips of alternating polarity (normal and
  reverse) lie as mirror images across the ocean
  ridges

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Paleomagnetism Preserved in Lava Flows
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Polarity of the Ocean Crust
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The Nature of Volcanic Eruptions

• Composition - silica makes magma more viscous
  (thick)
• Basaltic lavas are more fluid, rhyolitic and
  andesic lava is more viscous
• Temperature - Cooler temp. makes magma more
  viscous
• Dissolved gases in the magma - carbon dioxide,
  water vapor, and other gases
• The more viscosity and gases in magma, the more
  violent the eruption

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Volcanic Flows
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Volcanic Flows
Increasing viscosity
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Basaltic Magma at the Surface
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Pahoehoe (Ropy) Lava Flow
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Slow-Moving Aa Flow
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Anatomy of a Typical Volcano
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Shield Volcanoes

• Shield volcanoes
• broad, gently sloping volcanoes
• built from fluid, basaltic (low silica content)
  lavas

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Shield Volcanoes
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Cinder Cones

• Cinder cones are small volcanoes built from
  pyroclastic (ash, rock) material.
• Rhyolitic and andesic lava (high silica content)
• Steep slope
• Rather small in size
• Frequently occur in groups

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Cinder Cones
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Composite Cones

• Composite cones are volcanoes composed of both
  lava flows and pyroclastic (p. 103) material
• Rhyolitic and andesic lava (p. 103)
• Steep slope
• Large size
• Most violent type of activity

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Composite Cones
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Mount St. Helens Before and After the May 18,
1980, Eruption
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Profiles of Volcanic Landforms
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Magma Composition
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Convergent Boundary Volcano
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Kilauea, an Intraplate Volcano
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Earthquakes

• An earthquake is the vibration of Earth
• The focus is the point within Earth where the
  earthquake starts.
• The epicenter is the location on the surface
  directly above the focus.
• Faults are fractures in Earth where movement has
  occurred.
• Aftershocks follow the main earthquake
• Foreshocks precede the main earthquake

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Focus, Epicenter, and Fault
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Cause of Earthquakes

• Most earthquakes are produced by lithospheric
  plates moving against each other.
• When energy is built up and released, vibrations
  of an earthquake occur.

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Elastic Rebound Hypothesis
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Slippage Along a Fault
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Seismograph
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Seismogram
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Earthquakes Waves

• Seismographs are instruments that record seismic
  (earthquake) waves on seismograms.
• 3 kinds of seismic waves
• P waves come first
• S waves come second
• Surface waves are last

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Seismic Waves
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Seismic Waves Paths Through the Earth
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Earths Interior Showing P and S Wave Paths
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Locating an Earthquake
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Intensity Magnitude Scales

• Magnitude energy released at source of
  earthquake
• measured by the Richter Scale by calculating the
  amplitude (height) of the largest seismic wave
• Intensity the shaking felt and damage it did
• measured by the Mercalli Scale

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Magnitude vs. Intensity
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Earthquake Magnitudes
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Some Notable Earthquakes
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California Hazards

• Earthquakes and Volcanoes
• Along San Andreas Fault and other faults along
  the Pacific Plate, North American Plate, and Juan
  de Fuca Plate
• Fires
• Landslides
• Liquefaction saturated ground turns fluid, like
  quicksand
• Tsunamis caused when a quake sets an underwater
  landslide into motion

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Earthquake Damage
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Effects of Subsidence Due to Liquefaction
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Landslide Damage
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Movement of a Tsunami
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Californias Resources

• Water
• Limited precipitation (rain snow), surface
  water, and groundwater
• Carried in aqueducts (channels) from lakes,
  reservoirs, and rivers
• Most of it used in agriculture
• Minerals and Gas

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How to Read a Topographic Map

• Topographic maps represent Earths surface in
  three dimensions - elevation, distance
  directions, and slope angles
• Contour lines indicate elevation
• Contour interval is the distance in elevation
  between adjacent contour lines
• The closer the contour lines, the larger the
  slope

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Topographic Maps