lec 6 - GE105 Continents Adrift Continents Adrift 11...

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Unformatted text preview: GE105 Continents Adrift Continents Adrift 11 Reversals and seafloor spreading Lecture 1. Introduction and course overview. Lecture 2. Distance and time. Lecture 3. Planet building and Earth’s layered structure. Lecture 4. Wegener’s Continental Drift hypothesis. Lecture 5. Earth’s magnetic field and polar wander. Lecture 6. Reversals and seafloor spreading. Lecture 7. Plate tectonics – spreading and rifting. Lecture 8. Plate tectonics – collision zones Lecture 9. The wave that shook the world (movie) Lecture 10. Earthquakes I. Lecture 11. Earthquakes II. Lecture 12. Volcanoes and mantle convection Lecture 13. Final Exam (FEBRUARY 17, 2011) GE105 GE105 Continents Adrift GE105 Continents Adrift 22 Reversals of Earth’s magnetic field Computer simulations demonstrate that within a few thousand years ( instantaneously from a geologic point of view !) the Earth’s magnetic field spontaneously reverses every 200,000-300,000 years. Gary Glatzmaier, UC Santa Cruz normal in transition reversed GE105 Continents Adrift GE105 Continents Adrift 33 Reversals of Earth’s magnetic field Normal field (today) The field during a 5,000-10,000 year long reversal S N S N STRONG Dipole (90%) WEAK Quadrupole, octupole, … (10 %) Reversed field GE105 Continents Adrift GE105 Continents Adrift 44 Reversals of Earth’s magnetic field Before reversal: Decline of the dipole field...
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lec 6 - GE105 Continents Adrift Continents Adrift 11...

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