Lecture 6 Notes 9.9 - GS1004 Spotila 9 September 2016 Lecture 6 Plate Tectonics II Boundaries Motivating questions So the mantle convects and it drags

Lecture 6 Notes 9.9 - GS1004 Spotila 9 September 2016...

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GS1004 Spotila 9 September, 2016 Lecture 6: Plate Tectonics II - Boundaries Motivating questions: So the mantle convects, and it drags lithospheric plates around; what happens where the plates touch and move relative to each other? What imprint do plate boundaries leave on the Earth? If I want to stand on an active plate boundary, where do I have to go? 1) MID-OCEAN RIDGES Create new oceanic crust/lithosphere. Made by partial melting of mantle asthenosphere as it rises due to convection. Characteristics and important features: 1) basaltic magmatism, sea-floor spreading 2) ridge in sea-floor (buoyant) 3) age of oceanic crust 4) Extension: divergent motion on faults, like fissures. 5) Cold seawater interacts with magma; “hydrothermal circulation”. Entire ocean passes through ridges ~10 m.y.; 25% of Earth cooling.LOOK-UP ITEMS. Define "hydrothermal circulation". Where can you stand on a mid-ocean ridge? 2. SUBDUCTION ZONES: convergent (coming together) Rules: a) Oceanic lithosphere subducts (sinks) once cold (dense); recycled.
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  • Spring '08
  • AKSinha
  • Plate Tectonics, north american plate, active plate boundary

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