What are three things that are happening at plate boundaries?

Answer 1

Three things occur where lithospheric plates meet and a name has been given to each type of interface:

1) Divergent Boundaries occur in the ocean where magma from deep within the mantel rises to the rifts along oceanic ridges. The force of the rising lava flow pushes both plates away from the rift. once the lava cools, a new layer of oceanic crust is deposited along the ridge.

2) Convergent Boundaries occur at the deep ocean trenches that lie along continents and island arcs. The plate lithosphere subducts underneath the overlying oceanic or continental crust. This subduction occurs for two reasons: One, because the divergent side of the plate is being pushed by magma upwellings. And two, because the plate is being pulled downward by gravity at the interface of the deep ocean trench. If plate subduction did not occur at convergent plate boundaries than the surface area of earth would gradually increase over time as new strips of oceanic crust are solidified at divergent boundaries.

3) Transform Boundaries occur where two lithospheric plates move past each other with anti-parrallel paths. These boundaries can be found running perpendicular to oceanic ridges (divergent boundaries) in short segments.

Take a look at Google Maps or Google Earth and find the ridge system that runs down the center of the Atlantic Ocean like the seam of a Baseball. This "seam" is a Divergent boundary and volcanism occurs regularly as lava flows create new crust. You can also see the transform boundaries that run roughly perpendicular to the Mid-Atlantic ridge. If you now move all the way to the edge of japan that faces the Pacific Ocean you can see a convergent boundary. Notice the deep ocean trench where the Pacific plate is subducting underneath the Philippine and Eurasian plates.