Plate boundaries are found at the edge of lithosperic plates and are driven by radioactive heating that moves these plates laterally. The plates interact along marginal zones, which are classified into three types, convergent, divergent, and conservative. In areas of divergent boundaries, two plates move in opposite directions. Buoyant motions force the plates apart at rift zones where magma rises to form new oceanic crustal rocks. A shallow band of earthquakes caused by tensile stresses usually associated with these plate boundaries.
Lithosperic plates move toward each other along convergent plate boundaries.
When continental and oceanic plates come together, the edge of oceanic crust is pushed under the continental plate, which sometimes produces great mountain ranges. This boundary occurs in areas where ridges offset, and earthquakes seem to be more violent. Conservative plates on the other hand, slide parallel to onto one another in opposite directions. These areas are high seismicity, and build up sliding crustal slabs that generate thee world s deepest earthquakes. The surface layer of the earth is about 31 to 62 miles thick, and is suspected to be composed of a mixture of large and small tectonic plates.