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Unformatted text preview: Lecture 6- Earth as intergrated, Beginning of Evolution A. Evidence from Magnetism-  Lines of force from Earth’s magnetic field resembles those produced by a bar magnet, magnetic field on Earth varies in strength through time, can reverse  Periods of normal and reversed magnetic fields become locked in rocks as they cool B. Magnetic anomalies- lay across the sea floor, symmetric about axis of mid-ocean range where crust is created  Lateral motion caused by convection cells, some movement likely also from the tug of plates at subduction zones, also likely from the “tug” of plates C. Radiometric age dating of sea floor- youngest is the mid ocean ridge, oldest towards the continents  Plate tectonics explain distribution of earthquakes and volcanoes D. Hydrosphere- The Earth’s surface is covered by almost 71% oceans, no other planet in our solar system has liquid water on its surface  Liquid water may exist under the surface of some planets  Hydrospher- All the water on Earth, oceans, lakes, rivers, ice, air, soil, etc...
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- Winter '08
- Plate Tectonics, global average temperature, energy Geosphere atmosphere, energy F. Atmosphere