Plate Tectonics
Map of Plates Around World

The theory of plate tectonics states that there is a global distrubution of geological phenomena such a seismicity, continental drift, and mountain building in terms of the formation, destruction, movement, and interaction of the Earth's lithospheric plates.

Pangea Animation

The animation above shows how Pangea broke apart and moved into what it is today.

Convergent Boundaries
(Subduction Zones)

Subduction Zone          Subduction

A subduction zone, or a convergent boundary, is a place in the plates (usually involving at least one oceanic plate and sometimes a continental plate) where one plate goes under the other one and forms a trench. After the plate goed under and the other gets low enough into the asthenoshpere, the plate will melt and the magma will rise to the surface and form a volcano. (See above) If there is a subduction zone that consists of 2 plates that are continental crust, mountains will form from the collision of the 2 plates. (See below) The boundary between the Pacific plate and the North American plate is a good example of a subduction zone.

Divergent Boundary Land

 

Divergent Boundaries
(Ridges)

Divergent Boundary          Plates Diverging

A divergent boundary (usually occuring in 2 oceanic plates; also known as a rift) is a place where 2 plates are pull away from each other, and as they pull away from each other, magma comes out of the rift and forms new land. One rift can start as 2 plates of continental crust and can form into a whole ocean (See above). The Mid-Atlantic Ridge is an example of a divergent boundary.

Transform Boundaries
(Sliding Plates)
Transform Boundary         sliding plates


A transform boundary is where 2 plates come together and they rub together (each plate goes in an opposite direction) and neither plate loses any land. The San Andres Fault is an example of a transform boundary.


Hot Spots

Hawaii Hotspot          HOtspots


A hotspot (usually occurs in the middle of a plate) is a spot of magma in the asthenosphere while the lithospheric plates move over it. As they move, the magma pushes up through the plates to form volcanoes over many years. Over millions of years, the plate moves over the hotspot and the volcano eventually becomes inactive because the tunnel that the magma would traven up through to get to the volcano breaks off. As the years go on, the islands wear down from erosion and become sea mounds. If a hotsopt is under a crustial plate, a supervolcano can form if its a large enough spot (See Plate Tectonics behind Yellowstone and Yellowstone Disaster).