Lecture 20 Earth's Interior and Geophysical Properties.
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Transcript of Lecture 20 Earth's Interior and Geophysical Properties.
Lecture 20
Earth's Interior and Geophysical Properties
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
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
Controls on Seismic Wave Velocity
pressure
state of matter
composition of matter
Controls on Seismic Wave VelocityPressure
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
Controls on Seismic Wave VelocityState of Matter
Earth's Internal Structure
crust
mantle
core
Earth's Internal StructureThe Crust
MohorovicicDiscontinuity
(Moho)
Earth's Internal StructureCrustal Thickness
Earth's Internal StructureCrustal Thickness (United States)
Earth's Internal StructureThe Composition of the Crust
Earth's Internal StructureThe Mantle
Earth's Internal StructureThe Mantle
Mantle is Solid (S waves propagate)
Mantle is Rigid (seismic waves propagate)
Mantle is Fluid (convection cells present)
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
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
Earth's Internal StructureComposition of the Core
Iron
Nickel ~ 4%
Light Element (O or S) 10% by mass
Earth's Internal StructureMajor Discontinuities
crust/mantle - the MOHO
inside mantle (400 km and 670 km)
mantle/outer core (CMB)
outer/inner core (ICB)
Earth's Internal StructureMajor Discontinuities - The Moho
Earth's Internal StructureThe Core-Mantle BoundaryMAJOR Discontinuity
S-waves blocked by liquid outer core
Isostasy
the condition of equilibrium,comparable to floating, of theunits of the lithosphere abovethe asthenosphere.
Isostasy
Isostastic Adjustment
erosion and deposition
glacial rebound
crustal thickening
Isostastic AdjustmentErosion and Deposition
Isostastic AdjustmentGlacial Rebound
Isostastic AdjustmentCrustal Thickening
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).
Gravity
Gravity Anomaly
Gravity Anomaly
Gravity Anomaly
Gravity Anomaly
Earth's Magnetic Field
Earth's Magnetic Field
Rock Magnetism
Earth's Magnetic Field
Earth's Magnetic Field
Earth's Magnetic Field
Heat within the Earth
Heat within the Earth
Heat within the Earth
Sources of Earth's Heat
Pressure
Sunlight
Radioactive Decay
Primordial Heat
Redistribution of Earth's Heat
Radiation
Conduction
Convection
Redistribution of Earth's HeatConduction
Redistribution of Earth's HeatConvection