Lecture 20 Earth's Interior and Geophysical Properties.
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Transcript of Lecture 20 Earth's Interior and Geophysical Properties.
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Lecture 20
Earth's Interior and Geophysical Properties
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Lecture Outline
I Earth's Internal StructureA) The CrustB) The MantleC) The Core
i. Compositionii. Core-Mantle Boundary
IIIsostasyIII Earth's GravityIV Earth's Magnetic Field
A) Magnetic ReversalsB) Magnetic Anomalies
V Heat Within the EarthVI Conclusions
Lecture 20i
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Geophysics
photo by John Galetzka, USGS
geophysics: the branch of earthscience which employs physicalmeasurements and mathematicalmodels to explore and analyzethe structure and dynamics of thesolid Earth and other bodies andtheir fluid envelopes
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Controls on Seismic Wave Velocity
pressure
state of matter
composition of matter
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Controls on Seismic Wave VelocityPressure
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Controls on Seismic Wave VelocityComposition
Material Vp (ms-1) Density (gcm-3)Salt 4.6 2.2Quartz 6.1 2.7 Calcite 6.7 2.7 Dolomite 7.4 2.9 Siderite 7.0 4.0Pyrite 8.4 5.0
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Controls on Seismic Wave VelocityState of Matter
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Earth's Internal Structure
crust
mantle
core
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Earth's Internal StructureThe Crust
MohorovicicDiscontinuity
(Moho)
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Earth's Internal StructureCrustal Thickness
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Earth's Internal StructureCrustal Thickness (United States)
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Earth's Internal StructureThe Composition of the Crust
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Earth's Internal StructureThe Mantle
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Earth's Internal StructureThe Mantle
Mantle is Solid (S waves propagate)
Mantle is Rigid (seismic waves propagate)
Mantle is Fluid (convection cells present)
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Earth's Internal StructureThe Composition of the Mantle
Hofman Hart and Zindler Hutchinson Mason 1988 1986 1974 1966
SiO2 45.96 46.38 45.00 48.10
MgO 37.78 38.12 39.00 31.10
FeO 7.54 7.62 8.00 12.70
Al2O
3 4.06 4.10 3.50 3.10
CaO 3.21 3.24 3.25 2.30
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Earth's Internal StructureThe Core
Size: radius 3480 km (1/2 Earth)volume 1/8 Earthmass 1/3 Earth
Properties:density 10-13 g/cm3
pressure 136-330 GPatemperature 5500±1500 Kstate liquid-solid
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Earth's Internal StructureComposition of the Core
Iron
Nickel ~ 4%
Light Element (O or S) 10% by mass
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Earth's Internal StructureMajor Discontinuities
crust/mantle - the MOHO
inside mantle (400 km and 670 km)
mantle/outer core (CMB)
outer/inner core (ICB)
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Earth's Internal StructureMajor Discontinuities - The Moho
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Earth's Internal StructureThe Core-Mantle BoundaryMAJOR Discontinuity
S-waves blocked by liquid outer core
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Isostasy
the condition of equilibrium,comparable to floating, of theunits of the lithosphere abovethe asthenosphere.
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Isostasy
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Isostastic Adjustment
erosion and deposition
glacial rebound
crustal thickening
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Isostastic AdjustmentErosion and Deposition
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Isostastic AdjustmentGlacial Rebound
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Isostastic AdjustmentCrustal Thickening
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Gravity
gravity: the attraction between two masses,such as the Earth and an object on its surface. Commonly referred to as theacceleration of gravity (g).
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Gravity
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Gravity Anomaly
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Gravity Anomaly
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Gravity Anomaly
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Gravity Anomaly
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Earth's Magnetic Field
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Earth's Magnetic Field
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Rock Magnetism
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Earth's Magnetic Field
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Earth's Magnetic Field
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Earth's Magnetic Field
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Heat within the Earth
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Heat within the Earth
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Heat within the Earth
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Sources of Earth's Heat
Pressure
Sunlight
Radioactive Decay
Primordial Heat
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Redistribution of Earth's Heat
Radiation
Conduction
Convection
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Redistribution of Earth's HeatConduction
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Redistribution of Earth's HeatConvection