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Oceanography Ch 02
Earth Structure and Plate Tectonics
| Term | Definition |
|---|---|
| Andesite | a volcanic rock intermediate in composition between basalt and granite; associated with subduction zones. |
| Asthenoshere | a deformable region in the mantle where partial melting occurs…low seismic velocity…ductile behavior |
| Basalt | fine-grained, dark igneous rock, rich in iron and magnesium, characteristic of oceanic crust. |
| Continental Drift | the movement of continents; the name of Alfred Wegener’s theory, preceding plate tectonics. |
| Convection cell | circulation in a fluid, or fluidlike material, caused by heating from below. Heating the base of a fluid lowers its density, causing it to rise. The rising fluid cools, becomes denser, and sinks, creating circulation. |
| Convergent plate boundary | boundary a boundary between two plates that are converging or colliding with one another. |
| Inner core | innermost portion of the planet…solid…Fe and Ni in composition…rotates at a faster rate than the mantle…responsible for magnetic field... |
| Outer core | above the inner core…liquid… |
| Crust | outer shell of the solid Earth; the lower limit is usually considered to be the Mohorovicic discontinuity |
| Divergent Plate Boundary | a boundary between two plates that are diverging or moving apart from one another. |
| East pacific Rise | a divergent boundary in the eastern Pacific Ocean |
| Gondwanaland | an ancient landmass that fragmented to produce Africa, South America, Antarctica, Australia, and India introduced by Wegener |
| Granite | crystalline, coarse-grained, igneous rock composed mainly of quartz and feldspar. |
| Hawaiian Islands | Islands in the Pacific produced by a hot sot…tectonic in nature… |
| Emperor Seamount Chain | Islands Northwest of Hawaii, in the Pacific produced by a hot sot…tectonic in nature… |
| Heat Flow | Heat emmanating fro spreading centers |
| Hot spot | surface expression of a persistent rising plume of hot mantle material. |
| Isostacy | mechanism by which areas of Earth’s crust rise or subside until their masses are in balance, “floating” on the mantle. |
| Laurasia | an ancient landmass that fragmented to produce North America and Eurasia. |
| Lithosphere | outer, rigid portion of Earth; includes the continental and oceanic crusts and the upper part of the mantle. |
| Loihi | A new volcano rising from the southeast portion of te main island of Hawaii…due to a hot spot and plate tectonics… |
| Paleomagnetism | study of ancient magnetism recorded in rocks; includes study of changes in location of Earth’s magnetic poles through time and reversals in Earth’s magnetic field. |
| Magnetic field | A magnetic field is the magnetic influence of electric currents and magnetic materials |
| Magnetite | a mineral with the chemical composition of Fe3O4..a mineral with magnetic properties... |
| Mantle | main bulk of Earth between the crust and the core; increasing pressure and temperature with depth divide the mantle into concentric layers. |
| Mantle plume | A plume or column of hot molten rock that rises from the outer core through the mantle and expresses itself at the surface in the form of volcanoes |
| Mesosaurus | A Permian marine reptile used in verifiying Plate Tectonics… |
| Mid Atlantic Ridge | A spreading center in the middle of the Atlantic Ocean…extremely long... |
| Ocean trench | A feature of converging plates…deepest parts of the oceans |
| Ocean crust | crust below the deep-ocean sediments; mainly basalt. |
| Oceanic ridge | long, narrow elevation of the sea floor, with steep sides and irregular topography…conotes fast seafloor movement… |
| Oceanic rise | long, broad elevation that rises gently and generally smoothly from the sea floor…conotes slow seafloor movement… |
| P-waves | a type of seismic wave in which material is alternately compressed and stretched in the direction of propagation of the wave. |
| Seismic shadow zones | regions on the surface of the planet where P and S waves do not register on seismographs… |
| Pangea | an ancient landmass that consisted of all of the present-day continents; it fragmented into Laurasia and Gondwanaland…introduced by Wegener |
| Plate tectonics | theory and study of Earth’s Iithospheric plates, their formation, movement, interaction, and destruction; the attempts to explain Earth’s crustal changes in terms of plate movements. |
| Polar reversals | the periodic reversal of Earth’s magnetic field where the north magnetic pole becomes the south magnetic pole and vice versa. |
| Refract | change in direction, or bending, of a wave. |
| Rift valley | trough formed by faulting along a zone in which plates move apart and new crust is created, such as along the crest of a ridge system. |
| San Andreas Fault | A right-lateral transform fault that trends along the west coast of California…a boundary between the North American and Pacific Plates… |
| Seafloor spreading | movement of crustal plates away from the mid-ocean ridges; process that creates new crnstal material at the mid-ocean ridges. |
| Moment Magnitude | A scale used in seismology to measure the size of earthquakes in terms of energy released.. |
| S-waves | a type of seismic wave in which material is sheared from side to side, perpendicular to the direction of propagation of the wave. |
| Seismic waves | elastic disturbances, or vibrations, that are generated by earthquakes. |
| Spreading center | region along which new crustal material is produced. |
| Subduction zone | plane descending away froma trench and defined by its seismic activity, interpreted as the convergence zone between a sinking plate and an overriding plate. |
| Transform boundary | a boundary between two plates that are sliding past one another. This boundary is marked by a transform fault. |
| Transform fault | fault with horizontal displacement connecting the ends of an offset in a mid-ocean ridge. Some plates slide past each other along a transform fault. |
| Epicenter | point on Earth’s surface directly above an earthquake location, specified by identifying the latitude and longitude of the earthquake |
| Focus | the location of an earthquake within Earth. Focus is specified by identifying latitude, longitude, and depth of the earthquake. |
| Hydrothermal vent | seafloor outlet for high-temperature groundwater and associated mineral deposits; a hot spring. |
| Spreading rates | the rate at which two plates move apart. Spreading rates are generally between about 2 and 12cm (0.8 and 4.8 in) per year. |
Created by:
Permian
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