EES 1030 Lecture 12Outline of Last Lecture I. EarthquakesII. SeismologyIII. Distribution of EarthquakesIV. Measuring the size of earthquakesV. Earthquake DamageVI. TsunamisVII. Can earthquakes be predicted?Outline of Current Lecture VIII. Plate TectonicsIX. Continental DrifX. Supercontinent PangaeaXI. Seafloor spreadingXII. Geomagnetic ReversalsXIII. Magnetism of Seafloor RocksXIV.Three types of plate boundaryXV. What drives plate motionsXVI. Hot spots and mantle plumesCurrent LectureThese 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.- Plate Tectonicso Scientific Revolution in the late 1960s unifying concept of the Earth Scienceo LithosphereL Outer rigid shell of the Earth (-100 km) Consists of uppermost mantle & overlying crust. Divided into a series of rigid plateso Seven major plates & several smaller ones. Relative plate motions- Continental Drifo Recognition of jigsaw-puzzle fit of coasts on either side of Atlantico Alfred Wegener 1915: Continental drif hypothesis, large-scale horizontal movements f continents across Earth’s surfaceo Geometric evidence: computer best fit model using continental slope rather the coasto Remember: Not flat but Sphereo Fossil Evidence: Land-dwelling reptiles & plantso Paleoclimate evidence: evidence for ice sheets at 300 Ma in places now in tropicso Geological Evidence: Close match of rock types and structures between the continentso Many objections to Wegener’s hypothesis. Lack of mechanism for moving continents. Renewed interest in 1950’s initially came from rock magnetism.- Supercontinent Pangaeao When the continents were all connected, began to break up at 200 Ma- Seafloor Spreadingo 1950’s and 1960’s saw first concerted effort to investigate the geology of the Earth’s oceans.o Henry Hess (1962): new ocean crust at ridges- Geomagnetic Reversalso Earth’s magnetic field periodically changes polarity. Magnetic time scale- Magnetism of Seafloor Rockso Symmetrical linear anomalies across ridges- Three types of plate boundaryo Transform, Divergent, and Convergento Divergent: Seafloor spreading at ocean ridges: creation of new oceanic crust Constructive plate margin Convergent plate boundary: Oceanic lithosphere cools and contracts with increasing age – denser than asthenosphere. Continuous creation of ocean lithosphere- Subduction Zones: Oceanic trench & magmatism- Oceanic-Oceanic convergence: volcanic island arc. Examples: Aleutians, Marianas Continental Rifing: Continental crust splits apart at rif. Can lead to creation of new ocean.- What drives plate motionso Plate tectonics are the response to cooling of Earth. Thermal convective flow in the solid mantleo Slab pull: sinking of dense oceanic lithospheric slab- Hot spots and mantle plumeso Active volcanoes in the middle of the plate. Ex: