EARTHS INTERIOR GEOTEST3

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Anonymous
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25060
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EARTHS INTERIOR GEOTEST3
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2010-06-28 00:52:56
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EARTHS INTERIOR GEOTEST3
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EARTHS INTERIOR GEOTEST3
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  1. INTRO
    • A. STUDY the movement of earthquake(body) waves through earths interior
    • B. PATHS of seismic waves are bent(refracted) as they move
    • C. ABRUPT changes in velocities at discontinuities (boundaries)
  2. Layers Defined by Composition
    • A. CRUST
    • 1. Oceanic crust
    • a. 3-6 miles thick
    • b. Density = 3.0 g/cm
    • 2.Continental
    • a. 12-50 miles thick
    • b. Density=2.7g/cm
    • B.MANTLE
    • 1. Extends to 1800 miles
    • 2.Composed of peridotite
    • 3. Average density=4.5 g/cm
    • C. MOHO-CRUST mantle boundary
    • D. CORE
    • 1. Iron-nickel alloy
    • 2. Radious-2150 miles
  3. Layers Defined by Physical Properties
    • A.LITHOSPHERE(crust and uppermost brittle mantle)
    • 1. Cooler, rigid layer
    • 2.Averages 60 miles in thickness, but may be up to 150 miles below older parts of continents
    • B.ASTENOSPHERE(low velocity zone of the mantle)
    • 1. Soft,weak layer
    • C. MESOSPHERE
    • 1. Lower mantle (solid)
    • 2. Rocks hot and capable of very gradual flow
    • D. OUTER CORE
    • 1. Behaves as a liquid
    • 2. 1350 miles thick
    • 3.Average density=11 g/cm
    • 4. Convective flow of iron within zone generates Earths magnetic field
    • E. INNER CORE
    • 1. Behaves as a solid
    • 2. Radius 750 miles
    • 3.Average density=12.8 g/cm
    • 4.Rotates faster than rest of Earth
  4. Discovering Earths Major Layers
    • A.CRUST / mantle boundary (1909)-Velocity of P-waves increases abruptly below 30 miles
    • B. CORE-mantle boundary
    • 1. Located at about 2900 km
    • 2. P-Wave shadow zone (1914)
    • a. Area where direct P-waves are absent at seismic stations between 105-140 degrees from an EQ
    • b. P-waves are slowed and bent, so that few P-waves occur in shadow zone
    • C. LIQUID behavior of outer core (1926) S-Waves are completely blocked by core creating an S-waves shadow zone (105 to 256 degrees) frm an EQ
    • D. EXISTENCE of inner core (1936)- The weak P-waves observed in the P-wave shadow zone are refravted as they move from outer core to inner core

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