Continental Drift
Who came up with the hypothesis of continental drift?
Alfred Wegener
What technology was used to map the ocean floor?
SONAR
In which areas does subduction of the ocean floor take place?
deep trenches
What is the type of plate boundary where plates are being pulled apart?
Divergent
Wegener thought that all the continents were once joined together in a supercontinent that he called what?
Pangea
What is continental drift?
The theory that the continents are constantly moving
True or False: Convection currents help push magma from the mantle through the mid ocean ridge.
True
Explain what subduction is.
Subduction is when the more dense oceanic crust sink beneath the less dense continental crust at trenches.
What type of plate boundary occurs when plates are moving toward each other?
Convergent
What is the relationship between the distance from the mid-ocean ridge and the age of the oceanic crust?
The farther away from the ridge, the older the crust
Why was Alfred Wegener's hypothesis rejected?
Not enough evidence/people did not understand how continents drifted apart
Explain what mid ocean ridges are.
Underwater chains of volcanoes where magma is pushed up to create new seafloor
Why are the oldest parts of the ocean floor no older than about 200 million years old?
Old crust is subducted and gets thrown away back into the mantle as new crust is formed at mid-ocean ridges
What type of plate boundary occurs at mid-ocean ridges?
Divergent
True or False: Fossils of the same plant have been found in South America and Africa.
True
Explain at least 2 pieces of evidence that Alfred Wegener to support his hypothesis of continental drift.
Fossils, rocks/mountain ranges, climate
Explain what seafloor spreading is.
The formation of new seafloor at mid ocean ridges where the plates are pulled apart causing the seafloor to spread.
How does the density of oceanic crust differ from the density of continental crust? Why is this difference important?
Oceanic crust is more dense than continental crust. This is important because without the difference in density, subduction would not occur.
What type of boundary occurs when an oceanic plate subducts under a continental plate?
Convergent
What are the 2 sublayers of the earth? (one is located in the crust and the upper part of the mantle, the other is in the mantle)
Lithosphere and Asthenosphere
Which 2 continents fit together the best, making it apparent that they were once together?
South America and Africa
Explain how seafloor spreading and subduction works. (please use the following words: new crust, less dense, more dense, old crust, oceanic crust, continental crust, subduction, mid-ocean ridge).
Magma rises up through the mid-ocean ridge, solidifies into new crust and is then pushed away on either side. Since it gets pushed away over time, old crust can be found further away from the mid ocean ridge. When it reached the continents, the more dense oceanic crust sinks beneath the less dense continental crust in a process called subduction. The old crust is then cycles back into the mantle and becomes magma again.
If the seafloor is continually spreading, why isn't the Earth getting bigger?
Old crust is subducted back into the mantle so new crust is being form from recycled material. (matter cannot be created or destroyed)
What is plate tectonics?
The theory that the Earths lithosphere is divided into large plates that float on top of the asthenosphere. These plates move due to convection currents.
Explain how the movement of heat in the mantle drives the movement of convection currents.
Heat from the inner and outer core rises to the mantle, heating up the magma making is less dense so it can rise up through the mid-ocean ridge. When oceanic crust subducts, it is cooled down making it more sense so it sinks in the mantle. This cause the circular motion of convection currents.