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Transcript
The Solid Earth Earth’s Structure • Core • Mantle • Crust Earth’s Structure Earth’s Structure Core • Innermost portion of the earth • Inner core is VERY hot, but solid • Outer core is liquid molten material Mantle • Surrounds the core • Most is solid rock, but under the outermost part is a zone of hot, partly melted rock that flows like soft plastic called the asthenosphere Crust • Outermost and thinnest layer • Continental crust-under continents • Oceanic crust-under the oceans (71% of the crust) Internal Earth Processes • 2 kinds of movement of the earth – Convection cells: large volumes of heated rock that move following a pattern similar to the atmosphere (warmer is less dense) – Mantle plumes: mantle rock flows slowly upward, reaching the surface and spreading out (oceanic ridge) Convection Currents Mantle Plume Plate Tectonics • Tectonic plates (~60miles thick) consist of continental and oceanic crust and rigid outermost part of the mantle-called the lithosphere • Plates move constantly supported by the flowing asthenosphere • Produces mountains, oceanic ridges, trenches, etc. Plate Movment Plate Tectonics 3 Types of Plate Boundaries • Divergent plate boundary: plates move apart from each other • Convergent plate boundary: plates moving toward each other (earthquakes) • Transform Fault: plates slide past each other Divergent Plate Boundary Convergent Plate Boundary Transform Fault • http://www.youtube.com/watch?v=QDqsklt CixA External Earth Processes • Geologic changes based directly or indirectly on energy from the sun and gravity – Erosion – Weathering Erosion Erosion • Material is dissolved, loosened, or worn away from one part of the earth’s surface and deposited in other places – Streams – Wind – Human activities that accelerate erosion (acid rain) Weathering • Produces loosened materials that can be eroded • Two types – Mechanical (frost) – chemical Minerals • An element or inorganic compound that occurs naturally (solid) – Can be an element (gold) – Can be a combination of elements (salt, quartz) Rocks • Material that makes up a large, natural continuous part of the crust – Most consist of 2 or more minerals Three main Rock Types • Igneous • Sedimentary • Metamorphic Igneous • Formed when magma (molten lava) wells up, cools, and hardens; most of the earth’s crust – Granite – Lava Igneous Sedimentary • Formed from sediment that is weathered into smaller pieces, transported, and deposited into a body of water, pressed together, forming layers – Sandstone – limestone Sedimentary Metamorphic • Formed when preexisting rock partially melts, or is subjected to high pressure – Slate – marble Metamorphic Rock Cycle Natural Hazards-Earthquakes • Stress in the earth’s crust cause a fracture in solid rock, producing a fault • Energy is released as shock waves moving outward from the focus – Focus: point of initial movement – Epicenter: point on the surface directly above the focus Earthquakes Earthquakes • Magnitude measured by the Richter Scale • Seismograph measures amplitude of vibrations (each unit represents an amplitude that is 10X greater than the one before it) ex. An earthquake of 6.0 is 100x greater than a 4.0 – – – – – – Insignificant Minor Damaging Destructive Major Great <4.0 4.0-4.9 5.0-5.9 6.0-6.9 7.0-7.9 >8.0 Seismogram Earthquakes • Aftershocks can last up to 4 months • Foreshocks can occur seconds to weeks before main shock • Primary Effects: shaking, permanent ground displacement, damage to infrastructure • Secondary Effects: rock slides, urban fires, flooding, tsunamis • http://www.youtube.com/watch?v=g15sZ_d2WU Y Natural Hazards-Volcanoes • Magma reaching the earth’s surface • Can release: – Ejecta (rocks, debris) – Liquid lava – Gases (water vapor, carbon dioxide, sulfur dioxide) • Concentrated where there is seismic activity • Gases can remain in the atmosphere for up to 3 years, causing a cooling effect by as much as 1oF • http://www.youtube.com/watch?v=bgRnVhbfIKQ • http://www.youtube.com/watch?v=Hec9yKQQ4o Volcanoes Earthquake/Volcanic Activity