unit 6: dynamic planet: plate tectonics - ann arbor earth...
TRANSCRIPT
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Unit 6: Dynamic Planet: Plate Tectonics
Lecture 2
Objectives:E2.2C - Describe natural processes in which heat transfer in the
Earth occurs by conduction, convection, radiation.
E3.3B - Explain why tectonic plates move using the concept of heat flowing through mantle convection, coupled with the cooling and
sinking of aging ocean plates that result from their increased density.
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Heat Transfer *
Heat is always transferred from warmer to cooler objects
Mechanisms of heat transfer • Conduction through molecular activity • Convection
• Mass movement within a substance • Usually vertical motions
• Radiation (electromagnetic radiation) • Velocity: 300,000 kilometers (186,000 miles)
per second in a vacuum
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Mechanisms of heat transfer
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Mechanisms of heat transfer
Radiation (electromagnetic radiation) • Consists of different wavelengths
• Gamma (very short waves)• X-rays • Ultraviolet (UV) • Visible• Infrared• Microwaves and radio waves• Example: Uranium decay in Mantle Rx’s
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The electromagnetic spectrum
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What drives plate motion *
Several models have been proposed• Plate-mantle convection
• Mantle plumes extend from mantle-core boundary and cause convection within the mantle
• Models • Layering at 660 kilometers • Whole-mantle convection • Deep-layer model
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Layering at 660 kilometers
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Whole-mantle convection
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What drives plate motion *
Driving mechanism of plate tectonics • No one model explains all facets of plate
tectonics • Earth's heat is the driving force• Several models have been proposed
• Slab-pull and slab-push model • Descending oceanic crust pulls the plate • Elevated ridge system pushes the plate
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Several mechanisms contribute to plate motion