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Plate Tectonics
Earth 105
| Term | Definition |
|---|---|
| Divergent | plates move apart and a new oceanic crust is created by magma pushing up form the mantle. |
| Plate Tectonics | The Earth’s outermost rocky layer is divided into a small number of irregularly shaped Plates, which move as if they are internally rigid, hence all of the motion at the Earth’s surface occurs at Plate Boundaries. |
| Mid Atlantic RIdge | Volcanic country of Iceland straddles the Mid-Atlantic Ridge. Iceland is splitting along the spreading center between the North American and Eurasian Plates, as North America moves westward relative to Eurasia |
| Rift Zone | a large area of the earth in which plates of the earth’s crust are moving away from each other forming an extensive system of fractures and faults. |
| Convergent | (subduction zones): plates are moving toward each other, and sometimes one plate sinks (subducted) under another. The type of convergence (slow collision) depends on the kind of lithosphere involved |
| Subduction Zone | the location where sinking of a plate occurs. |
| Harry Hess | the earth’s unchanging size implies that the crust must be destroyed at about the same rate as it is created. |
| Oceanic-continental convergence: | sustains many of the Earth’s active volcanoes (ex: Andes and the Cascade Range). Eruptive activity is associated with subduction. Scientists debate how magma is created (melting of oceanic v. overlying continental) Ex: Nazca/S. Amer Plate create Andes |
| Oceanic-Oceanic convergence: | when two oceanic plates converge, one subducts and a trench is usually formed. Sometimes results in volcanoes (island arcs) – form from piled lava and volcanic debris until submarine volcano rises. EX: Marians Trench |
| Continental-Continental convergence: | when two continents meet head-on, neither is subducted because continental rocks are light. EX: Himalayan Mts |
| Transform | zone btwn 2 plates sliding horiz. past one another (transform-fault bound).These faults connect two centers(divergent plate bound or convergent plate bound).Found on ocean floor.Commonly offset spreading ridges,defined by shallow earthquakes.EXSanAndreas |
| Triple Junction | active splitting between the African Plate and Arabian Plate (where Red Sea meets the Gulf of Aden). |
| Seismology | Seismic waves radiate from the focus of an earthquake. Epicenter directly above focus, fault is actual line, wave fronts show the spread of the earthquake. |
| Primary Waves | arrival time |
| Secondary Waves | arrival time |
| Quakes Coda | length of seismic wave train |
| Earth Components | Crust, Mantle, Liquid Outer Core, Solid Inner Core |
| Crust | “Granitic”, officially Andesite (35km) – Continental Crust. |
| Mantle | Mantle Rocks,” officially Peridotite |
| Sir Harold Jefferys | argued it was physically impossible for a large mass of solid rock to plow through the ocean floor without breaking up. Effective critic of the feasibility of continental drift (skepticism of convection in the Earth’s mantle). |
| Beno Gutenberg | seismologist noted for his analyses of determining the intensity of Earthquake waves and the information they furnish about the physical properties of the Earth’s interior |
| Rock | a naturally occurring aggregate of minerals and other solid material. Usually several minerals in aggregate, though some rocks have one. Could be made of natural glasses, organic material – lignite, coaln or petroleum – or fossils |
| Mineral | naturally occurring inorganic solid, with a definite chemical composition, and ordered atomic arrangement. Quartz (SiO2), Potassium Felspar (KAISi3O8 |
| Rock Cycle | o Igneous Rocks: Crystallize from Magma • Yosemite Valley o Metamorphic (marble): formed when new minerals grow o Sedimentary: mostly made at earth’s surface • Alluvial Fan: Death Valley • Coastal Mud Flat: Alaska, GL • Limestone: UP |
| Gondwana Land Bridges | explanation for the geographic dispersion of species across regions that are now deep oceans. |
| Alfred Wegener | offered an alternative hypothesis for species dispersion-Continental Drift: the gradual movement of the continents across the earth’s. Fascinated with South America and Africa (look like they fit together). surface through geological time. |
| Occam’s Razor | “simplest is best” o A practical philosophy used everyday to decide what is simpler. o “The Principle of Least Astonishment” |
| Wegener’s Idea | the “grantic” continents, floating in the rock “sea” of basalt and mantle rocks, are like self-propelled rafts, pushing their way over the Basaltic layer. |
| Glacial Isotactic Rebound: | when land slowly rises after being pushed down by a glacier. |
| Isostasy | controls region elevations of continents&ocean floors in accord. w/dens. of underly rocks.Excess of mass seen as material +sea level (mtns) due to deficit of mass,low-density roots,-sea level.High mtns have low-dens roots extending deep in underly mantle. |
| Negative feedback: | feedback which the output quantity lowers the input quantity. Allows isostasty to restore equilibrium |
| Himalayans | the Grav effects of the Himalayas are less that we expect from the “+” mass anomaly seen. For the + mass anomaly that we see must be compensated by a negative mass anomaly at depth: “negative” with respect to the reference spheroidal symmetric Earth |
| Isotasty (geologically) | where the Earth’s strong lithosphere exerts stress on the weaker asthenosphere which, over geological time flows laterally such that the load of the lithosphere is accommodated by height adjustments. |
| Paleo-Magnetism | the study of the record of the Earth’s magnetic field in rocks (volcanic and sedimentary rock). A Key Early discovery was that the apparent latitude changed through geologic time at a particular site (indicates reversal, changes in angle). |
| Matuyama | proved the concept of pole reversal |
| Cox & Dalrymple | assign absolute Geologic ages to the pattern of magnetic reversal |
| Keith Runcorn (1950s): | the apparent polar wander curves for Europe and North America are different, they do overlap if you rotate them – which means you have to move the Continents so that they barely touch. Runcorn argued for Continental Drift with quantitative data |
| Arthur Holmes | pioneered the use of radioactive dating of minerals and was the first scientist to grasp the mechanical and thermal implications of mantle convection, which led eventually to the acceptance of plate tectonics. |
| Sea Floor Spreading | process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Helps explain continental drift. |
| Post WW2 | Oceanography jumps from minor activity to huge emphasis, many universities even buy ships. Oceanographers were making magnetic field measurements to find strength of magnetic field (basalt oozing up) |
| Harry Hess | discovered many seamounts during WW2, outlined a theory that could explain how the continents actually drift (Seafloor spreading). Believes ocean trenches are the location where ocean floor destroys and recycles |
| Mid Ocean Ridges | oceans were shallower in the middle and there were ridges raised above the surrounding generally flat sea foor (abyssal plain) |
| Vine & Matthews | basaltic magma comes up a just one place. Magma intrudes and erupts to form new oceanic lithosphere (positive polarity pushes crust away at center, alternates from there). |
| Lynn Sykes | trying ot explain why EQs only occurred between ridge segments. Isacks, Sykes, Oliver figured out Subduction Zones |
| JT Wilson | realized that sea floor spreading at the Ridge Crests only requires that the portion of the fracture zone between the ridges is active and his prediction was that the direction of slip is opposite to that of the traditional view |
| Deep oceanic trenches | along coastlines of japan, Indonesia, Madagascar, Alaska, Mexico, South America – some in middle of the ocean |
Created by:
micgiov
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