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24 Cards in this Set

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mapping the ocean floor
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
mid-ocean ridge
a system of underwater mounatains with a deep creack running through them.-rift valleys
mid-atlantic Floor
runs along the floor of the Atlantic Ocean
Rift Valleys
places where lava erupts from the valleys along the mid-ocean ridges-creating a new ocan floor
the scientist who developed the theory of the seafloor spreading moving and when?
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
mapping the ocean floor
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
mid-ocean ridge
a system of underwater mounatains with a deep creack running through them.-rift valleys
mid-atlantic Floor
runs along the floor of the Atlantic Ocean
Rift Valleys
places where lava erupts from the valleys along the mid-ocean ridges-creating a new ocan floor
the scientist who developed the theory of the seafloor spreading moving and when?
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
Rock ages
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
What other evidence was found besides magnetic and rock ages
life forms, giant tbe worms living on the ridges feeding off the chemical chemicals released from the valleys and ridges.
Magnetic feild
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
What happens if the poles reverse and how many times have they in the last _ years
if poles reverse they leave north pole and enter south pole
reversed 9 times in last 3.5 million years
How is evidence found of the poles reversing?
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
magnetometer
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
What did scientists find while using a magnetometer
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.
Magnetic Stripping
shows the ocean floor is spreading formed at different times.. it is evidence to prove sea floor spreading.. showing the contenents can move
Spreading Zones
occur at mid-ocean ridges and rift valleys It is wehre oceanic crust is created and older crust is pushed away
Subduction Zones
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
where do new rocks form and old rocks go
mid-ocean ridges- new rocks
trenches- old rock subducted
Subduction
process through which old oceanic crust is forced back into the earth at trenches
How old are the oldest rock found on the ocean floor
250 million years
How old are the oldest rocks found on continents?
3.6-3.9 billion years