Plate Tectonics and Earth’s Interior

Plate TectonicsPlate Tectonicsand Earth’s Interiorand Earth’s Interior

PangeaPangea

Distribution of Late Paleozoic Distribution of Late Paleozoic FossilsFossils

Conventional Wisdom:Conventional Wisdom:Animals Migrated Across Land BridgesAnimals Migrated Across Land Bridges

Late Paleozoic GlaciationLate Paleozoic Glaciation

Distribution of Ancient Mountain Distribution of Ancient Mountain BeltsBelts

Patterns Fit,Patterns Fit,But Is It Possible?But Is It Possible?

Tremendous amount of energy needed to move continents Tremendous amount of energy needed to move continents around the globearound the globe

Wegener proposed that centrifugal force on the spinning Wegener proposed that centrifugal force on the spinning Earth pushed continents from the south pole to the equator Earth pushed continents from the south pole to the equator

• Modeling/simulation indicated that this would be insufficientModeling/simulation indicated that this would be insufficient

Wegener proposed that the moving continents plowed Wegener proposed that the moving continents plowed through the oceans like an icebreakerthrough the oceans like an icebreaker

• Experiments indicated that oceanic rock is stronger than Experiments indicated that oceanic rock is stronger than continental rock, and so oceans would have cut through the continental rock, and so oceans would have cut through the continentscontinents

Continental Drift was a Model without a Mechanism!

Bathymetry of the Ocean FloorBathymetry of the Ocean Floor

Volcanoes of the WorldVolcanoes of the World

Volcanoes Correlate Globally with Volcanoes Correlate Globally with Deep EarthquakesDeep Earthquakes

Benioff Zone of SeismicityBenioff Zone of Seismicity

Plate Tectonic ModelPlate Tectonic Model

Tectonic PlatesTectonic Plates

Seismic WavesSeismic Waves

Seismic Wave VelocitiesSeismic Wave Velocities

Seismic Wave PathsSeismic Wave Paths

S-Waves P-Waves

Layers Within EarthLayers Within Earth

Convection Cells and Plate Convection Cells and Plate MovementsMovements

Plate Tectonic ModelPlate Tectonic Model

Differentiation: BasaltDifferentiation: Basalt

Partial melting of Partial melting of peridotite will form peridotite will form basaltic magmabasaltic magma

• Basaltic magmas Basaltic magmas are formed from are formed from melting mantle due melting mantle due to upwelling heatto upwelling heat

Differentiation: AndesiteDifferentiation: Andesite

Partial melting of Partial melting of basalt will form an basalt will form an andesitic or granitic andesitic or granitic magmamagma• Andesitic magmas are Andesitic magmas are

formed from melting formed from melting oceanic crustoceanic crust

• Subducting plate Subducting plate releases water (a flux) releases water (a flux) into mantle into mantle

• Magma pools under Magma pools under crust and partially melts crust and partially melts the oceanic crustthe oceanic crust

Differentiation: GraniteDifferentiation: Granite

Partial melting of Partial melting of andesite will form andesite will form granitic magmagranitic magma• Granitic magmas are Granitic magmas are

formed from melting of formed from melting of continental crustcontinental crust

• Subducting plate Subducting plate releases water (a flux) releases water (a flux) into mantle into mantle

• Magma pools under Magma pools under crust and partially melts crust and partially melts the continental crustthe continental crust

Sources of Heat for MetamorphismSources of Heat for Metamorphism Heat from Earth’s interiorHeat from Earth’s interior

Geothermal gradient is the Geothermal gradient is the increase in temperature with increase in temperature with depthdepth

• Typical continental geothermal Typical continental geothermal gradient is 25-30gradient is 25-30°C/km°C/km

• Volcanically active areas have Volcanically active areas have geothermal gradients of 30-geothermal gradients of 30-50°C/km50°C/km

• Oceanic trenches have Oceanic trenches have geothermal gradients as low asgeothermal gradients as low as5-10°C/km5-10°C/km