This graphic illustrates how volcanism causes
plate spreading (expansion causing "continental drift")
resulting in other plates being forced back under the earth's crust and being remelted.
Region
A |
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Region
B |
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Explantion of what you are seeing.
- Refer to the chart above.
- Notice the labels "Region A" in the Pacific and "Region B" in the Atlantic.
- Now imagine this graphic to represent the land mass between the two regions.
- As volcanism takes place on the Atlantic floor, the earth's crust and lithosphere are spread apart and new land mass is added in the form of lava (Region B).
- Remember the earth is a sphere, thus only a certain amount of spreading can take place before a weaker plate is forced under another plate (Region B).
- The combination of land mass being added and plates being spread apart, and other plates being forced back toward the center of the earth, causes the plates upon which the continents ride to "drift" or move over time.
- Land mass that is forced back to the center of the earth is remelted and many years later reemerges in the form of lava. Thus land is actually "recycled" over millions of years of time.
- Also keep in mind that the "spreading movement" caused by Region B (volcanism) results in transformational, compressional, or extensional plate movement -- thus continental plate movement is not in a straight line, but in many directions.
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