Chapter 2-1 - Click to edit Master title style 2 Plate...

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Unformatted text preview: Click to edit Master title style 2 Plate Tectonics and Physical Hazards The Big Picture • Pieces of Earth’s surface – Move around – Grind sideways – Collide – Sink into Earth’s hot interior • Collisions create mountain ranges, cause tsunami – Less directly, mountain ranges affect weather and climate Fig. 2-1, p. 15 Fig. CO-2, p. 14 Earth Structure • Layers of Earth based on rock composition: core, mantle, crust • Layers of Earth based on rock rigidity or strength: – Lithosphere is stiff, rigid outer rind of Earth, which makes up plates from 60 km (oceanic) to 200 km (continental) thick, including crust and denser underlying mantle – Asthenosphere is inner, hotter, more easily deformed layer Fig. 2-2, p. 15 Earth Structure • Continental crust – Silica-rich – Low density 2.7 g/cm 3 – 30-50 km thick – Stands higher than denser oceanic crust • Oceanic crust – Iron-, magnesium-rich, silica-poor – Higher density 3.0 g/cm 3 – 7 km thick – Floats lower than continental crust, on top of denser mantle Earth Structure • Elevation difference between continental and oceanic crust explained by isostacy – Floating solid object displaces liquid of same mass – Crust (continental or oceanic) floats atop mantle (denser mantle slowly flows away to accommodate crust) Height of a Floating Mass Height to which floating block rises above fluid is proportional to the density of the floating block relative to the density of the fluid Fig. 2-BTN1, p. 16 Earth Structure • Boundary between crust and mantle identified as density difference: Mohorovicic Discontinuity (Moho) • Boundary between lithosphere and asthenosphere has been identified as zone of lower velocity for seismic (earthquake) waves traveling through mantle: low-velocity zone (LVZ) Plate Movement • Lithosphere is broken into about 12 large plates , most of which are combination of continental and oceanic areas, moving up to 11 cm/year Fig. 2-3, p. 17 Plate Movement • Plates move away from each other at divergent boundaries – usually mid-oceanic ridges • Plates move toward each other at convergent boundaries – Subduction zone : one plate dives under other, into mantle – Continent-continent collision : low density of continents prevents subduction, crumple up into each other instead • Plates slide past each other at transform boundaries Fig. 2-4, p. 18 Fig. 2-5, p. 19 Stepped Art Asthenosphere Inner core Mantle Outer core Upwelling Hot Cold Continental lithosphere Trench Midoceanic ridge Ocean Subduction zone Oceanic lithosphere Fig. 2-5, p. 19 Fig. 2-6, p. 19Fig....
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This note was uploaded on 03/28/2011 for the course GEO 107 taught by Professor Stidham during the Spring '08 term at SUNY Stony Brook.

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Chapter 2-1 - Click to edit Master title style 2 Plate...

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