Subduction
What is subduction?
The process by which ocean floor sinks beneath a trench and back into the mantle.
where does the molten materials come from???
the mantle
What did Wegener believe about the continents?
He believed that the continents were once a supercontinent, but drifted apart.
what device was used to map out or measure the mid-ocean ridge??
Sonar(a system using sound pulses)
what causes subduction???
caused by molten material getting pushed up out o the mid-ocean ridge and into a trench
what happens to the old rock on the sea floor??
it gets push away from the mid- ocean ridge when magma gets pushed up.
Why did scientists not believe Alfred Wegener's theory on the Pangaea?
He knew that the contentants spread but didn't know how. He didn't have enough evidence.
True or false: Pillow lava rocks did not prove sea floor spreading.
False
What is a deep-ocean trench???
a deep underwater canyon
what causes sea-floor spreading???
convection currents in the mantle
In what year did Hess prove his theory on sea-floor spreading?
1960
How did rocks in the sea floor prove sea floor spreading?
They found that the farther away from a ridge the samples were taken, the older the rocks were.
true or false: The process of of subduction can change the size and shape of oceans.
true
where does sea-floor spreading happens????
underwater on the mid-ocean ridge
True or false: Wegener put forth his theory in 1923
False. It was 1912
How did pillow-like rocks under the sea show proof of sea floor spreading?
Scientists found that the rock could only be made by eruptions of lava underground, showing that that was the reason rock was spreading.
true or false the Pacific ocean is spreading???
false
How do the convection currents in the layers of the earth have to do with sea-floor spreading?
Heat from large convection currents in the mantle transfer heat to the surface, where magma pushes out or mid-ocean ridges.
How did Harry Hess learn about sea-floor spreading?
He learned when he was on a mission to study the deep sea floor when he was fighting in World War 2.
When was the last magnetic reversal of Earth??
Around 780,000 years ago.