Oceanography Ch 3
Essentials of Oceanography
Terms
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- Plate Tectonics
- Theory that Earth's lithosphere is fractured into plate that move relative to each other and are driven by convection currents in the mantle
- Convergent Plate Boundary
- Region where plates are pushing together and where a mountain range, island arc, trench will usually form
- Seafloor Spreading
- Theory that new ocean crust forms at spreading centers
- (John Tuzo) Wilson
- Canadian geophysicist who proposed theory of plate tectonics in 1965
- convection zone
- isostatic equilibrium
- Subduction
- Downward movement into the asthenosphere of a lithospheric plate
- Density Stratification
- Formation of layers in a material, with each layer deeper being denser than the layer above
- Subduction Zone
- Area at which a lithospheric plate descends into asthenosphere
- Continental Crust
- Primarily granite
- Lithosphere
- Earth's cool, rigid outer layer; 100-200km thick; comprises continental and oceanic crusts and uppermost layer of mantle
- Fault
- Fracture in a rock mass along which movement has occurred
- Core(s)
- Primarily iron and nickel
- Spreading Center
- Junction between two divergent plates at which ocean floor is being made
- Superplume
- Very large mantle plume
- Transform Fault
- Plane along which rock masses slide horizontally past one another
- Lower Mantle
- Extends to core; does not melt b/c of high pressure
- Mantle Plume
- Ascending columns of superheated mantle originating at the core-mantle boundary
- Asthenosphere
- Hot, partially melted, slowly flowing layer of upper mantle; 350-650km
- Mantle
- Primarily oxygen, iron, magnesium, and silicon
- Convection Current
- Single closed-flow circuit of rising warm material and falling cool material
- Magnetometer
- Device that measures amount and direction of residual magnetism in a rock sample
- Granite
- Speckled rock composed mainly of oxygen, silicon, and aluminum
- Continental Drift
- Theory that continents move slowly across the Earth
- Transform Plate Boundary
- Places where crustal plates shear laterally past one another; crust is neither produced nor destroyed
- Basalt
- Heavy, dark colored rock composed mainly of oxygen, magnesium, and iron
- Seismic Waves
- Low frequency pulses of energy generated by the forces that cause earthquakes
- Oceanic Crust
- Primarily basalt
- Hot Spot
- Surface expression of a plume of magma rising from a stationary source of heat in the mantle
- Paleomagnetism
- Remnant magnetic field of a rock
- Rift Valley
- Linear lowland between mountain ranges usually caused by crustal expansion
- Terrane
- isolated segment of seafloor, island arc, continental crust, or sediment transported by seafloor spreading next to a larger continental mass; usually diff in comp than larger mass
- Isostatic Equilibrium
- Balanced support of lighter material in heavier, displaced supporting matrix