The Earth

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The Earths Internal Properties
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I. Seismic Waves

• A. Earthquake-generated waves traveling
  through the Earths interior
• B. Give us clues to the composition of the Earth

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C. Types of Seismic Waves

• 1. Surface waves
• travel on the Earths surface
• 2. Body waves
• travel through the Earths interior

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Body waves

• P-waves (primary waves)
• Compress and expand rock
• Are the fastest of all seismic waves
• First waves to register on seismograph

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Body waves

• b. S-waves (secondary waves)
• Vibrate up and down
• Second waves to register on a seismograph

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Seismograph Device which measures seismic waves
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II. Earths internal layers

• Geologists did research with seismic waves
• Concluded that the Earths
• interior is layered.

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Earths internal layers
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Earths internal layers

• A. The Core-
• 1. Composed mostly of iron and nickel
• 2. Inner Core
• very hot
• solid Fe Ni due to high pressure of the Earth

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The Core (continued)

• 3.Outer Core
• less pressure from the earth
• liquid Fe Ni
• Flow in the outer core generates an electric
  current that powers the Earths magnetic field.

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B. The Mantle

• Rocky layer
• About 3000km thick

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1. Two parts of mantle

• a. Lower mantle
• b. Upper mantle
• two sections

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b. Upper mantle

• Asthenosphere - behaves in a semi-fluid
  manner

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b. Upper mantle

• ii. Lithosphere- rigid and brittle

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C. The Crust

• Uppermost portion of the lithosphere
• Two types of crust
• a. Oceanic crust - about 10 km thick

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C. The Crust

• b. Continental crust
• about 20-60 km thick

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III. Theory of Continental Drift

• A. Belief that the earth is a dynamic planet with
  the continents in constant motion (i.e.
  continents are moving)

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III. Theory of Continental Drift

• B. All continents once joined together into
  supercontinent called Pangea
• (meaning all land)
• C. Theory formulated by Alfred Wegener

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III. Theory of Continental Drift

• D. Evidence that supports theory
• 1. Geologic (rock)
• 2. Biologic (life)
• 3. Climatological (past weather)
• 4. Continental Shelves fit together very
• well

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Tectonic Plates

• moving sections of the lithosphere
• on which continents lie

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IV. Faults

• fault a fracture along which visible
  displacement can be detected on one side relative
  to the other.
• Types of faults
• 1. Footwall-Fig 23.17
• (one on bottom)

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Footwall
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B. Types of faults

• 2. Hanging wall- Fig 23.17 (one on top)

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V. Vertical movement along a fault

• 1. Reverse Fault- Fig 23.18- Footwall down
• Examples
• Rocky Mountains
• Canadian Rockies
• Appalachian Mts.

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V. Vertical movement along a fault

• 2. Normal Fault- Fig 23.19- Footwall up

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VI. Horizontal movement along a fault boundary
(Fig. 23.22)

• Transform-fault boundary
• plates are sliding past one another
• (Figs. 23.27 28)
• E.g. San Andreas fault in
• California
• ? Earthquakes caused by sheering forces

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B. Divergent Boundaries

• 1. two plates are moving apart
• (Fig. 23.23) ? Plate A Plate B ?
• 2. Creates rift valleys
• large spreading valleys
• at fault line
• 3. Creates sea floor spreading-
• a rift valley on sea floor
• 4. Caused by tensional forces

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B. Divergent Boundaries
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C. Convergent Boundaries

• 1. Two plates move towards each other
• (Fig 23.24)
• Plate A ? ? Plate B
• 2. Leads to subduction- one plate
• (usually oceanic crust)
• goes beneath the other
• (continental crust).
  
• Caused by compressional forces

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C. Convergent Boundaries
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C. Convergent Boundaries

• E. g. Andes Mountains in S. America
• (Still growing because of subduction)
• 3. ?Common place to find volcanoes
• E.g. Cascade Range
• (Mt. St. Helens, Mt. Rainier)

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Tectonic Plate Movement
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Major Tectonic Plates