1 Chapter 2: The Earth’s Mobile Crust Plate Tectonics The Earth’s interior Plate Boundaries Continental Margins Tectonic Classification of Coasts Tectonic effects on coastal sediment supply Continental Drift-Plate Tectonics continents had once been together Alfred Wegener 1920’s Rejected (gravity Earth, Moon, Sun) Continental Drift-Plate Tectonics New evidence Sea floor mapping Magnetic anomalies Earthquake distribution Heat flow Radiometric dating Satellites Theory of Mantle Convection (Hess, 1960s) Shallow epicenters- Crustal movement Mid-deep epicenters subduction Seismic refraction = change in speed of P & S waves Factors Chemistry Density Physical State (liquid or solid) Layered Structure of Earth
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Chapter 2: The Earth’s Mobile Crust
Plate Tectonics
The Earth’s interior
Plate Boundaries
Continental Margins
Tectonic Classification of Coasts
Tectonic effects on coastal sediment supply
Continental Drift-Plate Tectonics continents had once been together
Seismic refraction = change in speed of P & S waves
FactorsChemistryDensityPhysical State (liquid or solid)
Layered Structure of Earth
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Formation of the Universe, Solar System, Earth
– Big Bang, 13 bya– Formation of elementary particles– Gravitational formation of dense regions– 12 bya first stars– 4.55 bya Rotating cloud of gas from which sun
and planets formed, initiated by “supernova” = exploding star
– Accretion (Gaining material)– Differentiation (Separating based on density)– Evidence of rocks and water- 3.9 bya
Layered Structure of EarthInner core: r=1222km, primarily Fe & Ni T=4000-5500COuter core: 2258km thick, 3200C, liquid (partially melted)
Layered Structure of EarthMantle: 70% Earth’s volume, 2866m thick, 100-3200C,
Mg-Fe silicates, solid but can flowMohorovicic discontinuity: chemical boundary between
Mantle and Crust
Layered Structure of EarthContinental Crust:
Primarily granitic type rock (Na, K, Al, SiO2)40km thick on averageRelatively light
Oceanic CrustPrimarily basaltic (Fe, Mg, Ca, low SiO2)7km thickRelatively dense
Layered Structure of Earth (Physical Properties)
Lithosphere: 100km thickRigid slab (plate)
Asthenosphere350km thickPartially melted
(P,T,H2O)Mesosphere
Extends to mantle-core boundaryPressure=compact mineralogy, mechanically
Fan like deposit where the continental slope intersects the abyssal plains
Formed by turbidity currents
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Tectonic Evolution of Continental Margins
Atlantic Margin: passive margin, edge of the continent is in the middle of a lithospheric plate, little seismic activity, no volcanism
Pacific Margin: active margin, edge of the continent coincides with a plate boundary, rim of the Pacific Ocean, ring of fire, seismic activity and volcanism
Tectonic Setting (Pacific-vs-Atlantic type margin)
Tectonic Setting of opposite side of the continent