lecture14spring2009

lecture14spring2009 - Astronomy100Dr.Rhodes...

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Astronomy 100 - Dr. Rhodes Lecture #14 - 2/18/2009
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Chapter 6: The Earth-Moon System Plate Tectonics Plate Tectonics German meteorologist Alfred Wegener is credited with developing in 1910 the idea of continental drift — the gradual motion of the continents relative to one another. The Earth’s crust and the outer 40 miles of its mantle comprise the lithosphere , which is broken into about 12 tectonic plates . A rift zone is a place where tectonic plates are being pushed apart, normally by molten material being forced up out of the mantle.
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Alternative View of Parts of Earth’s Interior in which the Outer Mantle and the Crust are Called the Lithosphere and Asthenosphere
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Chapter 6: The Earth-Moon System The Mid-Atlantic Ridge One such rift zone runs down the spine of a undersea mountain range that is located roughly halfway between Europe and the U.S. and halfway between Africa and South America. This range is called the Mid- Atlantic Ridge . The observations associated with this Mid- Atlantic Ridge are what finally convinced geophysicists that Wegener was right, e.g., the Ridge is hot and earthquakes do occur there.
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Chapter 6: The Earth-Moon System Sea-Floor Spreading Where the warm magna that is rising within the mantle reaches the Earth’s surface, it must stop flowing vertically and must begin to flow horizontally. This horizontal motion of the ocean floors is called sea-floor spreading . Because of this spreading Africa and South America have been separating for 150 million years and the oldest sea floor rocks are those near both continents.
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Chapter 6: The Earth-Moon System Subduction Zones and Convection Where a denser sea floor plate is sliding into the edge of a less-dense continental plate, the material in the sea floor plate dips into the Earth and slides beneath the continental plate. Such a location on the Earth is called a subduction zone . The plates are thought to be moved by the
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This note was uploaded on 03/03/2009 for the course ASTR 100 taught by Professor Rhodes during the Spring '08 term at USC.

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lecture14spring2009 - Astronomy100Dr.Rhodes...

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