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Transcript
Plate Tectonics Why Continents and Ocean Basins Exist Topics • Density Structure of Earth • Isostasy • Sea-Floor Spreading • Mechanical Structure of Earth • Driving Mechanism of Plate Tectonics • Lithospheric Plate Interactions • Plate Tectonics and the Depth of the sea floor Topics • Density Structure of Earth • Isostasy • Sea-Floor Spreading • Mechanical Structure of Earth • Driving Mechanism of Plate Tectonics • Lithospheric Plate Interactions • Plate Tectonics and the Depth of the sea floor Mechanical Structure of Earth Mechanical Structure of Earth A different way to view the structure of Earth To understand how the crust moves, scientists view the structure of Earth in a different way To understand how the crust moves, scientists view the structure of Earth in a different way Geologist use this structure because the crust does not move by itself To understand how the crust moves, scientists view the structure of Earth in a different way Geologist use this structure because the crust does not move by itself The crust and the upper mantle move as a unit Review Review The density structure of Earth is based on two criteria: 1. Density 2. Composition Mechanical Structure of Earth Mechanical Structure of Earth Use this structure when discussing plate motions Mechanical Structure of Earth Use this structure when discussing plate motions Structure based on two criteria: Mechanical Structure of Earth Use this structure when discussing plate motions Structure based on two criteria: 1. Strength Mechanical Structure of Earth Use this structure when discussing plate motions Structure based on two criteria: 1. Strength 2. Viscosity Mechanical Structure of Earth Mechanical Structure of Earth The mechanical structure of Earth has four layers: Mechanical Structure of Earth The mechanical structure of Earth has four layers: 1. Lithosphere Mechanical Structure of Earth The mechanical structure of Earth has four layers: 1. Lithosphere 2. Asthenosphere Mechanical Structure of Earth The mechanical structure of Earth has four layers: 1. Lithosphere 2. Asthenosphere 3. Mesosphere Mechanical Structure of Earth The mechanical structure of Earth has four layers: 1. Lithosphere 2. Asthenosphere 3. Mesosphere 4. Core Mechanical Structure of Earth Structure of Earth based on strength and viscosity 1. Lithosphere --- outside 2. Asthenosphere 3. Mesosphere 4. Core --- inside Mechanical Structure of Earth Structure of Earth based on strength and viscosity 1. Lithosphere --- outside 2. Asthenosphere 3. Mesosphere 4. Core --- inside Mechanical Structure of Earth Lithosphere Lithosphere Includes all of the crust and the upper mantle Lithosphere Includes all of the crust and the upper mantle Averages 80 km thick Lithosphere Includes all of the crust and the upper mantle Averages 80 km thick Relatively strong compared to the asthenosphere Lithosphere Includes all of the crust and the upper mantle Averages 80 km thick Relatively strong compared to the asthenosphere Tends to resist stress to the point of fracture Lithosphere Includes all of the crust and the upper mantle Averages 80 km thick Relatively strong compared to the asthenosphere Tends to resist stress to the point of fracture Relatively high viscosity Lithosphere Includes all of the crust and the upper mantle Averages 80 km thick Relatively strong compared to the asthenosphere Tends to resist stress to the point of fracture Relatively high viscosity Relatively low temperature Lithosphere Lithosphere Includes all of the crust and the upper mantle Averages 80 km thick Relatively strong compared to the asthenosphere Tends to resist stress to the point of fracture Relatively high viscosity Relatively low temperature Isostasy The lithosphere floats on the asthenosphere Asthenosphere Asthenosphere Underlies the lithosphere Asthenosphere Underlies the lithosphere Averages 300 km thick Asthenosphere Underlies the lithosphere Averages 300 km thick Relatively weak compared to the lithosphere Asthenosphere Underlies the lithosphere Averages 300 km thick Relatively weak compared to the lithosphere Tends to flow when stressed Asthenosphere Underlies the lithosphere Averages 300 km thick Relatively weak compared to the lithosphere Tends to flow when stressed Relatively low viscosity Asthenosphere Underlies the lithosphere Averages 300 km thick Relatively weak compared to the lithosphere Tends to flow when stressed Relatively low viscosity Relatively high temperature The asthenosphere is the source of magma that forms the sea floor The mesosphere is the largest part of Earth The mesosphere is the largest part of Earth The mesosphere is hotter but more viscous than the asthenosphere The mesosphere is the largest part of Earth The mesosphere is hotter but more viscous than the asthenosphere The outer core is molten Fe The mesosphere is the largest part of Earth The mesosphere is hotter but more viscous than the asthenosphere The outer core is molten Fe The inner core is solid Fe The Driving Mechanism of Plate Tectonics Next The Driving Mechanism of Plate Tectonics Definition Back Definition Viscosity - measure of the resistance to flow Back Definition Viscosity - measure of the resistance to flow For example, water has a low viscosity, it flows easily Back Definition Viscosity - measure of the resistance to flow For example, water has a low viscosity, it flows easily Glass has a high viscosity, it strongly resists flow Back Mechanical Structure of Earth
