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24 Cards in this Set
- Front
- Back
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mapping the ocean floor
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new ways to map invented in 1940s & 50s. sound waves allowed scientists to map large areas. Waves echo off the bottom- longer it takes sound waves to bonce back the deeper it is. translate into pict. Side-scan sonar waves use sound waves to produce a pict. of the ocean floor- picts show many features
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mid-ocean ridge
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a system of underwater mounatains with a deep creack running through them.-rift valleys
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mid-atlantic Floor
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runs along the floor of the Atlantic Ocean
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Rift Valleys
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places where lava erupts from the valleys along the mid-ocean ridges-creating a new ocan floor
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the scientist who developed the theory of the seafloor spreading moving and when?
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Harry Hess proposed in 1960s that less dense magma rose grom below the crust and forced its way up at mid-ocean ridges and rift valleys ..this molten material flows sideways carrying and pushing ocean floor ocean floor away from mid-ocean ridge cooling and creating a new ocean floor
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mapping the ocean floor
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new ways to map invented in 1940s & 50s. sound waves allowed scientists to map large areas. Waves echo off the bottom- longer it takes sound waves to bonce back the deeper it is. translate into pict. Side-scan sonar waves use sound waves to produce a pict. of the ocean floor- picts show many features
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mid-ocean ridge
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a system of underwater mounatains with a deep creack running through them.-rift valleys
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mid-atlantic Floor
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runs along the floor of the Atlantic Ocean
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Rift Valleys
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places where lava erupts from the valleys along the mid-ocean ridges-creating a new ocan floor
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the scientist who developed the theory of the seafloor spreading moving and when?
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Harry Hess proposed in 1960s that less dense magma rose grom below the crust and forced its way up at mid-ocean ridges and rift valleys ..this molten material flows sideways carrying and pushing ocean floor ocean floor away from mid-ocean ridge cooling and creating a new ocean floor
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Rock ages
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in 1968 scientists aboard the Glomar Challange found the youngest rocks on the ocean floor were near mid-ocean ridges-farther from the ridges older the rocks
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What other evidence was found besides magnetic and rock ages
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life forms, giant tbe worms living on the ridges feeding off the chemical chemicals released from the valleys and ridges.
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Magnetic feild
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the earth's magnetic feild has a north and south pole. The feild is created as magnetic forces leave near the south Pole and enter the north Pole
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What happens if the poles reverse and how many times have they in the last _ years
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if poles reverse they leave north pole and enter south pole
reversed 9 times in last 3.5 million years |
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How is evidence found of the poles reversing?
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Igneous rocks forming along rift valleys and mid-ocean ridges register the earth's magnetic properties as the cool--Any changes or reversals will be registered in iron-bearing minerals
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magnetometer
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detects a strong magnetic reading when the polarity of a rock has the same polarity that the earth's magnetic feild presently has, normal polarties show up as peaks
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What did scientists find while using a magnetometer
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scientist found that rocks on the ocean floor showed many periods of reversals
reversals created matching stripes on either side of the mid-ocean ridge. |
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Magnetic Stripping
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shows the ocean floor is spreading formed at different times.. it is evidence to prove sea floor spreading.. showing the contenents can move
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Spreading Zones
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occur at mid-ocean ridges and rift valleys It is wehre oceanic crust is created and older crust is pushed away
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Subduction Zones
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occur at V-shaped valleys known as trenches on the ocean-floor. Trenches-deepest part of ocean.. Old oceanic crust forced back into the earth @ trenches & recycled into the mantle called subduction
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where do new rocks form and old rocks go
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mid-ocean ridges- new rocks
trenches- old rock subducted |
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Subduction
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process through which old oceanic crust is forced back into the earth at trenches
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How old are the oldest rock found on the ocean floor
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250 million years
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How old are the oldest rocks found on continents?
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3.6-3.9 billion years
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