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Ocean chap 2

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plate tectonics
global dynamics having to do with the movement of a small number of semirigid sections of Earth's crust, with seismic activity and volcanism occuring primarily at the margins of these sections. this movement has resulted in changes in the geographic positions of continents and the shape and size of ocean basins.
Alfred Wegener
german meteorlogist and geophsicist. first to advance the idea of mobile continents in 1912.
Continental drift
a term applied to early theories supporting the possibility the continents are in motion over Earth's surface
Pangaea
an ancient supercontinent of the geologic past that contained all earth's continent
Panthalassa
a large, ancient ocean that surround pangaea
Tethys sea
an ancient body of water that seperated Laurasia to the north and Gondwanaland to the south. its location was approximately that of the present Alpine-Himalayan mountain system
ice age
the most recent glacial period, which occured during the Pleistocene epoch
Mesosaurus
an extinct, presumably aquatic reptile that lived about 250 million years ago, and located only in eastern south america and western africa
Magnetic field
a condition found in the region around a magnet or an electric current, characterized by the existence of a detectable magnetic force at every point in the region and by the existence of magnetic poles
magnetite
a naturally magnetic iron mineral
paleomagnetism
study of earths ancient magnetic field
magnetic dip
degree to which a magentite particle points into earth
polar wandering curves
a curve that shows the change in the position of a pole through time
polarity
the directional orientation of the magnetic field
magnetic anomalies
distortions of the regular pattern of earths magnetic field resulting from the various magnetic properties of local concentrations of ferromagnetic minerals in earths crust
sea floor spreading
a process producing the lithosphere when convective upwelling of magma along the oceanic ridges moves the ocean floor away from the ridge axes at rates between 2 to 12 centimeters per year
convection cells
a circular moving loop of matter involved in convective movement
mid-ocean ridge
continuous underwater mountain range that winds through every ocean basin in the world and resembles the seam of a baseball
spreding center
a divergent plate boundary
ocean trenches
deepest parts of the ocean floor and resemble a narrow crease or trough
subduction
the process by which one lithospheric plate descends beneath another as they converge
subduction zone
a long narrow region beneath earths surface in which subduction takes place
mantle
the zone between the core and crust of earth, rich in ferromagnesium minerals
flux
the quantity of heat flow to earths surface per unit of time
lithosphere
the outer layer of earths structure, including the crust and the upper mantle to a depth of about 200 km, major components involved in plate techtonic movement
asthenosphere
a plastic layer in the upper mantle 80 to 200 km deep that may allow lateral movement of lithospheric plates and isostatic adjustments
divergent boundaries
a lithospheric plate boundary where adjacent plates diverge, producing an oceanic ridge or rise
convergent boundaries
a lithospheric plate boundary where adjacent plates converge, producing ocean trench-island arc systems, ocean trench-continental volcanic arcs, or folded mountain ranges
transform boundaries
the boundary between two lithospheric plates formed by a transform plate
rift valley
a deep fracture or break, about 25 to 50 km wide, extending along the crest of mid-ocean ridge
rifting
the movement of two plates in opposite directions such as along a divergent boundary
oceanic rises
gently sloping and fast-spreading parts of the mid-ocean ridge
east pacific rise
oceanic rise between pacific and nazca plate. broad, low, gentle swelling of the sea floor with a small, indistinct central rift valley
oceanic ridges
steeper-sloping and slowe-spreading areas of the mid ocean ridge
mid atlantic ridge
oceanic ridge between south american and african plates. tall, steep, rugged oceanic ridge
seismic moment magnitude
earthquake intensity is measured on a scale, which reflects the energy released to create very long period seismic waves
volcanic arc
melting in the subduction zone causes an arc shaped row of highly active and explosively erupting volcanoes that parallel the trench
continental arc
an arc shaped row of active volcanoes produced by subduction that occurs along convergent active continental margins
island arc
a linear arrangement of islands, many of which are volcanic, usually curved so that the concave side faces a sea seperating the islands from a continent. the convex side faces the open ocean and is bounded by a deep-ocean trench
transform faults
a fault with side to side motion that offsets segments of a mid-ocean ridge
oceanic transform fault
transform fault that occurs wholly on the ocean floor
continental transform fault
transform fault that cuts across a continent
transform faulting
movement of one plate past another-produces shallow but often strong earthquakes in the lithosphere
san andres fault
continental transform fault that runs from the gulf of california past san francisco and beyond into northern california
hotspots
areas of intense volcanic activity that remain in more or less the same location over long periods of geologic time and are unrelated to plate boundaries
mantle plumes
columnar areas of hot molten rock that arise from deep within the mantle
nematath
a chain of extinct volcanoes that is progressively older as one travels away from a hotspot
seamounts
tall volcanic peaks on the ocean floor
tablemounts or guyots
tall volcanic peaks conical on the top on the bottom of the ocean floor
coral reef
a calcareous organic reef composed significantly of solid coral and coral sand
fringing reefs
intially develop along the margin of a landmass where the temperature, salinity, and turbidity of the water are suitable for reef builiding corals
great barrier reef
largest reef system in the world.
atoll
a ring-shaped coral reef growing upward from a submerged volcanic peak. it may have low-lying islands composed of coral debris
paleogeography
study of historical changes of continental shapes and positions
continental accretion
growth or increase in size of a continent by gradual external addition of crustal material
wilson cycle
a model that uses plate techtonic processes to show the distinctive life cycle of ocean basins during their formation, growth, and destruction