Planet Earth Week 1 Fall 2016
Planet Earth Week 1 Fall 2016 Geol 105
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This 4 page Class Notes was uploaded by Abi Sommers on Thursday August 25, 2016. The Class Notes belongs to Geol 105 at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by John Platt in Fall 2016. Since its upload, it has received 218 views.
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Date Created: 08/25/16
8/24 Global Tectonics Lithosphere includes upper part of mantle and crust that overrides the mantle represents departure from normal mantle w/in earth’s body Upper part of mantle increase in temperature as goes downward, mantle rocks that do melt and mantle rocks that do, partial melting Plate Boundary: Boundary between asthenosphere and lithosphere Global Topography and Bathymetry(topography below sea level) Seismic belts separated by large areas of planet where there are not earthquakes. Earthquakes are release of energy when crust shifts along a fault “Fault” means there must be some movement between stable areas, plates *Not until 1968 marine geologists found plates , spatial areas of earths crust shaping with respect to each other Mid Atlantic Ridge is a boundary between two stable areas Plates can move, together, beneath, and past Divergence (together), Convergence (beneath), Transform Plate Motion (past) ● 1857 last movement of San Andreas fault Coastal California slips past North America @ 55 kms per 1 million years *Continents have changed shapes and positions throughout time, reconstructions of Earth’s supercontinent; Pangea *Pangea built up of convergence of plates on other sides of the world When continental crust extends, confining pressure reduced Reduction of pressure allows existing high temp at depth to partially melt mantle Large volume of mole rocks (magma) rise up along axis of plate rifting, eventually new basaltic ocean crust *East Africa shows early stages of same continental extension that led to evolution of rifted Red Sea in the north, one day could be as wide as the atlantic ocean *Volcanic midocean ridges and rises are direct expression of where hot mantle rises near to earth’s surface. Initial seafloor spreading happened between North Africa and North America Different parts of Atlantic Ocean opened before others Divergent boundaries Rifting and spreading along a narrow zone have created Mid Atlantic Ridge ; A mid ocean mountain chain where volcanoes and earthquakes are concentrated. *Central Atlantic between Eastern U.S and North Africa began to form first ,nearly 180 million years ago Breakup of pangea created 3 ocean basins Atlantic, Arctic and Indian Ocean Pacific was already there Generation of oceanic lithosphere along ridge and rise system known as, sea floor spreading, and process occurs at different rates 70% of earth’s crust formed in last 180 million years , only 4% of earth’s history 8/26 *Sea floor spreading hidden beneath oceans Iceland extensional plate boundary between Europe and N. American plates exposed at earth’s surface Iceland part of Mid Atlantic ridge Mid Atlantic Ridge enters at Thingvallir, one of first settlement areas in Iceland Island extending, divided by European plate and N. American plate Basaltic magma has built island by rising along vertical fractures Bardarbunga volcanic eruption 20142015 largest basalt eruption since 1700s. Added 1.5 km of lava over 6 mo. ^ Plate divergence Plate convergence : 3 types: Oceanic plate moves beneath oceanic plate Oceanic plate beneath continental plate Continental plate beneath continental plate Plate convergence and subduction Most common; oceanic plate goes below continental plate ● Juan de Fuca plate being subducted beneath U.S Pacific Northwest and Southern British Columbia, slow but fast enough to produce earthquakes. Vancouver, Seattle Portland all at risk. (last earthquake jan. 16 ,1700) subducting plate carries water rich ocean crust to beneath coastal N. America. Plate heats, dehydrates and water moves upward Earthquake hypocentre is starting point of earthquake from seismic waves travel outward Oceanic plate beneath Oceanic plate: Mariana Arc characterized by small islands Mountain systems w/in Alpine Mediterraneaniranianhimilayan orogenic belt. Belt created by collisions btwn eurasia and southern continental plates Earths most spectacular example of crustal deformation Alpine Himilayans Boundary today continuing tectonic activity *Parts of eastern medittereanean still have oceanic crust beneath them Highest elevation in the world is Tibet ; 15,000 feet. *Height of mass related to thickness ^ indian crust sitting beneath Asian crust India once part of supercontinent, as broke loose, began to move northward because attached to oceanic plate, being subducted to the North. Transform Plate Motion: two plates moving past each other, sometimes left slip, sometimes right slip *San Andreas transform fault