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Transcript
Plate Tectonics and Earth’s Interior Pangea Distribution of Late Paleozoic Fossils Conventional Wisdom: Animals Migrated Across Land Bridges Late Paleozoic Glaciation Distribution of Ancient Mountain Belts Patterns Fit, But Is It Possible? Tremendous amount of energy needed to move continents around the globe Wegener proposed that centrifugal force on the spinning Earth pushed continents from the south pole to the equator • Modeling/simulation indicated that this would be insufficient Wegener proposed that the moving continents plowed through the oceans like an icebreaker • Experiments indicated that oceanic rock is stronger than continental rock, and so oceans would have cut through the continents Continental Drift was a Model without a Mechanism! Bathymetry of the Ocean Floor Volcanoes of the World Volcanoes Correlate Globally with Deep Earthquakes Benioff Zone of Seismicity Plate Tectonic Model Tectonic Plates Seismic Waves Seismic Wave Velocities Seismic Wave Paths S-Waves P-Waves Layers Within Earth Convection Cells and Plate Movements Plate Tectonic Model Differentiation: Basalt Partial melting of peridotite will form basaltic magma • Basaltic magmas are formed from melting mantle due to upwelling heat Differentiation: Andesite Partial melting of basalt will form an andesitic or granitic magma • Andesitic magmas are formed from melting oceanic crust • Subducting plate releases water (a flux) into mantle • Magma pools under crust and partially melts the oceanic crust Differentiation: Granite Partial melting of andesite will form granitic magma • Granitic magmas are formed from melting of continental crust • Subducting plate releases water (a flux) into mantle • Magma pools under crust and partially melts the continental crust Sources of Heat for Metamorphism Heat from Earth’s interior Geothermal gradient is the increase in temperature with depth • Typical continental geothermal gradient is 2530°C/km • Volcanically active areas have geothermal gradients of 3050°C/km • Oceanic trenches have geothermal gradients as low as 5-10°C/km