GEOS 212 1st Edition Lecture 3 Outline of Last Lecture 1. Layering of Earth: 1) Crust/Mantle/Core (chemistry)); versus 2) Lithosphere/ Asthenosphere / Rest of Mantle / Outer Core / Inner Core (mechanical properties)2. Continent versus Ocean, Continental crust versus Oceanic crust, mantle, lithosphere, asthenosphere (draw diagram)3. Plate Tectonics explains opening and closing of ocean basins, growth and shrinking of plates, movement of plates, and most earthquakes and volcanoes.4. Plate tectonics: plates (crust + uppermost mantle (~100km total) are rigid and move overa very weak, but not molten), asthenosphere5. Plate Boundaries (Divergent, Convergent, Transform)6. Divergent Boundaries (aka Spreading Centers, Mid-Ocean Ridges) are where new plate iscreated (~5cm/yr); sit ~2km above rest of seafloor because they are warm7. Diagram of spreading centers -- how oceanic crust is made8. Animation of spreading centers9. Video of ocean floor at spreading center- height of spreading center?- length of spreading center?- water temperature?- big surprise when first discovered?10. Spreading centers on the World Map => world tour!11. History of the South Atlantic & opening of new oceans in generalOutline of Current Lecture 1. History of spreading in South Atlantic, North Atlantic, Eastern Pacific, Labrador Sea, and Indian Ocean2. Rates of spreading: rate is distance / time, usually km/my or cm/yra. The edge of the continent is usually not sea level, but the edge of thecontinental shelf3. Pacific Plate also has chain of islands from hot spot = Hawaii!These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Connection between mantle plume, hot spot, island chainb. Rate of motion calculation: distance / time, usually km/my or cm/yr4. Subduction zones in continental and oceanic settings5. Plate tectonics is the most efficient way for the earth to lose heat … that’s the simple reason that plates move.6. Early idea was that conveyor-belt convection ‘drives’ plate, but it has problems7. Some people now believe that plates slide away from ridges and toward subduction zones8. World Tour of subduction zones Current LectuWhat did we learn today?• Plates move because PLATE TECTONICS is the most efficient way for the Earth to lose heat.• Some people think plates slide away from RIDGES and toward SUBDUCTION ZONES.• The youngest seafloor is located at the RIDGES.• The oldest seafloor is located at edges of the CONTINENTS OR OCEAN BASINS.• Spreading rates are determined by dividing DISTANCE by AGE, and rates are in Km/my or cm/yr.• Plates move over HOT SPOTS and create a chain of volcanoes• Plate is destroyed at SUBDUCTION ZONE.• Only OCEANIC plate subducts under either OCEANIC or CONTINENTAL
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