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What are they Thinking? • The Search for the source of Energy to provide the Force necessary to move the continents away from each other. • Then Explain How it Works? Magma & Floating Crusts Less Dense Continental Crust Floats higher in the Mantle Denser Oceanic Crust Floats lower in the mantle Viscous Magma (like hot glass) within the Mantle © Beadle, 2009 Earths Interior produces Heat Very Hot Rock Crust Very Cold Rock 2-3,000 F ≈64 F Core Energy: Nuclear Decay Heat Mantle © Beadle, 2009 Even Hotter Rock. (Different Material) 12,000 F Convection Currents: A possible Convection Current Review explanation of how the continents move. Hot fluid rises Crust Crust Warms back up again. Cools at the surface Moves the stuff at the top © Beadle, 2009 Cooler fluid sinks Hot fluid rises back up Heat Demo: Oil & Thyme Plate Tectonics Divergent (Spread Apart) Upwelling New Rock Formed Mid Ocean Ridges © Beadle, 2009 Convergent Core Energy: Nuclear Decay Heat Mantle (collision) Down welling Old Crust Destroyed Mountains Volcanoes Trenches Heat as the source of energy Mountains, Volcanoes & Trenches Mountains © Beadle, 2009 Divergent Geologic Features Mid Ocean Ridge Old Ocean Crust New New Old Ocean Crust • Convection cells provide the force to move the continents. • The crust is carried on its back. • The ridge is a result of less dense hot rock. © Beadle, 2009 Convergent Plate Boundary Geologic Features Mtn / Volcano Ocean Trench New Ocean Crust Old • Convection cells provide the force to move the continents. • The crust is carried on its back. • The trench is a result of the denser crust sub ducting below the less dense crust. © Beadle, 2009 Continental Crust Zone of Earthquakes ~8-9.0 M Transform • Most common between the other plate boundaries. • Two plates moving side by side • Common medium sized earthquakes – ~6.0 – 7.0 So, How & Why do: • • • • • Mountains Form Volcanoes Form Ocean Trenches Form Mid Ocean Ridges Form Earthquakes Happen Earthquakes • Earthquakes happen when the surfaces of two plates slide past one another. • Tensional Forces overcome Frictional Forces. – Earthquakes happen as a result of the plates being in motion. Friction & Tension • Tension & Strain Builds up • Overcomes Static Friction • Snaps • Unleashes stored energy. • (A Fault is a plane of weakness) Demo: have students put knuckles together, press and slide. Click for Video Demo on Faults How we sense seismic energy • Seismographs Click for Seismograph Animation How Volcanoes Form • When magma from below is less dense than the surrounding rock, it rises and punches through. Blam ! Overlying Rock Ash, Gasses, Pressure etc. Overlying Rock Pressure is Overcome by internal Pressure Gas Pressure Magma © Beadle, 2009 Types of Energy Associated with Volcanoes • Thermal Energy • Mechanical Energy • Light Energy – (Glow & least effective for change) • These energies combined change the earths surface How Mountains, Trenches & Island Arcs Form • Mountains, Volcanoes & Sometimes Trenches form when two plates collide. • These are formed at Convergent Plate Boundaries How Mountains & Volcanoes Form pm Hot Magma © Beadle, 2009 Cooler Crust pm How Mountains & Volcanoes Form pm Hot Magma © Beadle, 2009 (compression) pm Volcanic Explosion Extrusive Igneous Rock pm Hot Magma © Beadle, 2009 pm How Mountains, Trenches & Island Arcs Form • Mountains, Volcanoes & Sometimes Trenches form when two plates collide. – Ocean to Ocean – Continental to Continental – Continental to Ocean • All are at Convergent Plate Boundaries Crustal Collisions Continental v. Oceanic Less Dense Continental Crust Floats higher in the Mantle Denser Oceanic Crust Floats lower in the mantle Viscous Magma (like hot glass) within the Mantle © Beadle, 2009 Convergent Plate Boundary Geologic Features Mtn / Volcano Ocean Trench New Ocean Crust Old • Convection cells provide the force to move the continents. • The crust is carried on its back. • The trench is a result of the denser crust sub ducting below the less dense crust. © Beadle, 2009 Continenta l Crust Zone of Earthquakes ~8-9.0 M Crustal Collisions Continental v. Continental Less Dense Continental Crust Floats higher in the Mantle Less Dense Continental Crust Floats higher in the Mantle Viscous Magma (like hot glass) within the Mantle © Beadle, 2009 Crustal Collisions Oceanic v. Oceanic Denser Oceanic Crust Floats lower in the mantle Denser Oceanic Crust Floats lower in the mantle Viscous Magma (like hot glass) within the Mantle © Beadle, 2009 Convergent Geologic Features Island Arc Volcano Ocean Trench New Ocean Crust Old • Convection cells provide the force to move the continents. • The crust is carried on its back. • The trench is a result of the denser crust sub ducting below the less dense crust. © Beadle, 2009 N. Oceanic Crust Zone of Earthquakes ~8-9.0 M Divergent Plate Boundary (Split Apart) -Most common in the middle of oceans (mid-ocean ridges) -Two plate moving apart from each other -Many small earthquakes Divergent Geologic Features Mid Ocean Ridge Old Ocean Crust New New Old Ocean Crust • Convection cells provide the force to move the continents. • The crust is carried on its back. • The ridge is a result of less dense hot rock. © Beadle, 2009 O N O Transform • Most common between the other plate boundaries. • Two plates moving side by side • Common medium sized earthquakes – ~6.0 – 7.0 Plate Tectonics Divergent (Spread Apart) Upwelling New Rock Formed Mid Ocean Ridges © Beadle, 2009 Convergent Core Energy: Nuclear Decay Heat Mantle (collision) Down welling Old Crust Destroyed Mountains Volcanoes Trenches Heat as the source of energy Mountains, Volcanoes & Trenches Mountains © Beadle, 2009
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