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29 Cards in this Set
- Front
- Back
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oceanic crust
-covered by -thickest near -thinnest near -made of |
-sediment
-continents -mid-ocean -mafic (basalt and gabbro) |
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what is mafic
-def -composition similar to |
-igneous rocks
-earths mantle |
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what characterizes the mid-ocean ridges (1)
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-high heat flow
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sea-floor spreading hypothesis
-who -time -essay title -provide a potential mechanism for |
-henry hess
-1960 -essay in geopoetry -continental drift |
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sea-floor spreading hypothesis
-mantle erupts at ___ -crust moves away from ridges, gathers ___ -at ___, sea floor dives back into the ___ |
-mid ocean ridges
-sediment -trenches, mantle |
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what are marine magnetic anomalies
-def (2) |
-magnetometer, magnetic anomaly
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-___ is an instrument that measures the strength of the earth's magnetic field in rocks
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-magnetometer
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-difference between expected strength and actual measured mag field
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-magnetic anomaly
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what are two types of magnetic anomalies
-types & def |
-positive-strength of measured mag field is stronger than expected
-negative-strength of measured mag field is weaker than expected |
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marine magnetic anomalies
-towed magnetometers measure __ -magnetism varies ___ to the ___ ridge -the variations are ___ and ___ mag anomalies -anomalies are ___ that parallel ___ ridges |
-ocean crust
-perpendicular, mid ocean - +, - -linear belts, mid ocean |
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interpretation of marine magnetic anomalies
- positive - def - negative - def |
-magnetic field recorded by rocks adds to the force made by earths mag field
-mag field recorded by rocks subtracts from the force made by earths mag field |
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why does this interpretation of marine magnetic anomalies occur
-earths mag field reverses ___ over time |
-polarity
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what are the 2 types of polarity
-___ polarity-__ geographic pole and __ magnetic pole coincide -___ polarity-__ geographic pole and __ magnetic pole coincide |
-normal, N, N
-reverse, N, S |
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-positive marine magnetic anomaly occurs where ___
-negative marine magnetic anomaly occurs where ___ |
-ocean floor rocks record normal polarity
-ocean floor rocks record reverse polarity |
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sea-floor spreading explains the stripes
-magnetic anomalies are ___ across a __ ridge |
-symmetric, mid-ocean
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sea-floor spreading explains the stripes
-magnetic anomalies mimic layered ___ -magnetic "___" form as ___ cools at a mid-ocean ridge -___ crust spread away from ___ ridge -sea-floor spreading is the mechanism of ___ |
-lava flows
-stripes, lava -ocean, mid-ocean -continental drift |
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drilling in the late 1960s recovered crust samples
-ages ___ away from the mid-ocean ridge -ages are "____" across the mid-ocean ridge |
-increase
-mirrored images |
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plate tectonics
the paradigm of "how the earth works" -earth's other shell is broken into ___ that move - ___ change the face of the planet -allows scientists to ___ and ___ |
-rigid plates
-moving plates -predict events, rebuild the past |
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Plate Tectonics
provides a unified mechanism explaining: -___, ___ and ___ rocks -the distribution of ___ and ___ -origin of ___ and ___ -distribution of ___ and ___ -the genesis and destruction of ___ -continental ___ |
-igneous, sedimentary, metamorphic
-earthquakes, volcanoes -continents, ocean basins -mountains -drift |
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Plate Tectonics
-earth's ___ is broken into ___ that move |
outer shell, tectonic plates
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-tectonic plates are fragments of ___
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-lithosphere
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-___ is made of both crust and upper mantle and is in motion over the ___
-bends __ when loaded |
-lithosphere, asthenosphere
-elastically |
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-flows plastically when loaded
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-asthenosphere
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Tectonic Plate Boundaries
-lithosphere is fragmented into ~ __ tectonic plates -plates move continuously at a rate of __ to __ cm/yr -plates ___ along their boundaries -plate ___ are almost earthquake free |
-20
-1, 15 -interact -interiors |
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3 types of plate boundaries
-tectonic plates move apart -tectonic plates move together -tectonic plates slide sideways |
-divergent
-convergent -transform |
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Divergent Boundaries
-sea-floor spreading causes plates to move ___ -___ fills up the gap -___ cools, ___ material to each plate |
-apart
-magma -magma, adding |
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Ocean Crustal Age
-oceanic crust ___ from the ridge axis -___ crust is closer to the ridge -___ crust is farther away -oldest oceanic crust is found at the far edge of the ___ |
-spreads away
-newer -older -basin |
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Convergent Boundaries
-___ plates move toward one another -___ - one plate dives back into the mantle; is always ___ -___ recycles oceanic lithosphere |
-lithospheric
-subduction, oceanic lithosphere -subduction |
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Subduction
-old oceanic lithosphere is ___ dense than mantle -a ___-lying oceanic plate doesn't subduct easily -once bent ___, the leading edge ___ |
-more
-flat -downward, sinks |
