Section 4
Section 4
Section 4
Section 5
Section 5
100
What was Hess’ idea of sea-floor spreading?
At the mid-ocean ridge, molten material rises from the mantel and erupts. The molten material then spreads out pushing older rocks to both side of the ridge. Hess’ theory helps wegener’s theory
100
What was the Glomar Challenger?
It was boat – a drilling ship. It gathered samples. The Glomar Challenger sent drilling pipes through water 6 km deep to drill holes in the ocean floor.
100
Where would denser oceanic crust be found?
Far from the mid-ocean ridge.
100
Why is the atlantic ocean expanding?
It is expanding because it has less trenches compare to the pacific. The ocean has virtually nowhere to go. Therefore, it is expanding.
100
What are three types of plate boundaries?
Transformed, divergent, and convergent
200
What are the evidences that support Hess’s theory of sea-floor spreading?
Molten materials, magnetic stripes, and drilling samples.
200
How did drilling sample show evidence of ocean floor spreading?
Scientists took the samples and determined the age of the rock. Rocks that were farther away from the ridge were OLDER. Younger rocks were found near the ridge. This all proves sea-floor spreading
200
Where do newly formed oceanic crust lie?
Near the mid-ocean ridge.
200
What are plates?
Cracks in the lithosphere that split up the lithosphere into sections.
200
What are divergent boundaries?
The place where two plates move apart. Most divergent boundaries occur at mid-ocean ridge
300
What was Alvin? And what was Alvin used for?
It a submersible built to withstand crushing pressure 4 km down the ocean. He was used down to find molten material.
300
What are deep- ocean trenches?
Deep under-water canyons
300
Where do older formed oceanic crust lie?
Away from the mid-ocean ridge.
300
What is the theory of plate tectonics?
It explains the formation movement and subduction of earth’s plates.
300
What forms along a divergent boundary?
Rift valley
400
What did Alvin discover?
Pillow lava…proves there’s molten material
400
What is subduction and where does it occur?
Subduction is the process by which the ocean floor sinks beneath a deep ocean trench and back into the mantle . Then via CONVECTION CURRENT, new oceanic crust pushes back up and forms near the mid-ocean ridge. The older oceanic crust gets push to the side. It occurs at the deep ocean trench
400
About how many years does the Earth’s ocean floor renewed itself?
200 million years
400
What are plate boundaries?
Plate boundaries are the areas where the different plates meet
400
What is a rift valley?
Forms along divergent boundary and it is a deep valley
500
How did magnetic stripes show evidence of ocean floor spreading?
Because the magnetic field reverses, it changes the way the sea floor spread. The ocean floor rocks form stripes in the same pattern as magnetic stripes. The rock of the ocean floor contains iron and began as molten material. When the material cools, the iron bits line up in the direction of the Earth’s magnetic poles. The parallel stripes of the rock match the stripes of the magnetic field.
500
What does subduction allow the ocean floor to do?
Subduction allows deep ocean trenches to sink back into the mantle.
500
Why is the pacific ocean shrinking?
It is shrinking because when the deep ocean trench swallows more oceanic crust then the mid-ocean ridge can produce, then the ridge does not add new crust fast enough. The width of the ocean will shrink.
500
What are faults?
Breaks in Earth’s crust where rocks have slipped past each other.
500
What are convergent boundaries?
When two plates converge (hit each other)
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