What is Plate Tectonics?
VPlate Tectonics is the movement of the earth’s continents (or plates) over the face of the planet. The jigsaw puzzle fit of the continents of North and South America to Africa was first noticed in the late 18th century by Francis Bacon, and the theory of continental drift was first published in 1912 by a German meteorologist and geophysicist named Alfred Wegener. However, it was not until the 1960’s that scientists put together many ideas into what we now know as the accepted theory of Plate Tectonics.
What Causes the Continents to Move?
Continental Drift is thought to be caused by gravity, and that the continents own weight is what causes them to move. The explanation for this is that since the plates are slightly denser than the lower asthenosphere, they tend to sink. They are known to gently slide down gentle slopes such as ocean ridge crests and lower subduction zones. Once the plate’s leading edge reaches the subduction zone the rest of the plate tends to be pulled toward the trench. This is known as the slab-pull.
The second cause for plate movement is known as Convection Currents. Convection Currents are the movements of molten material circulating deep within the earth. Convection Currents occur when hot, molten, rocky material becomes denser and begins to sink again, moving in a circular pattern. This was once thought to be the primary driving force of plate movement, but it is now believed that the currents are an effect in sinking plates that contributes to the overall movement of the plates.
Scientists have also proposed the concept to thermal plumes, upright columns of molten material that are an additional force of plate movement. Unlike convection currents they do not circulate but rather rise up through the asthenosphere and appear on the surface as hot spots. They may originate within the asthenosphere or even deeper within the boundary between the mantle and the core.
Where will the Continents move in the Future?
In the future the Pacific Ocean will continue to close at a rate of about 4 inches per year. The Atlantic will continue to open as the North American and South American Plates move west. The Eurasian and Antarctic plates are not moving significantly so the Indian Ocean is not presently moving. The Australian Plate is just beginning to collide with the plate that forms Southeast Asia. Also, India will continue to slam into Asia and will eventually slide all the way under it.
Techtonic Plates of the Earth