Many of us learned the basics of plate tectonics in school. Yet only six decades ago, it was more theory than reality. Today, it helps us understand how our fundamental planetary geophysical system works.
Basically, the Earth’s surface is made up of eight major and several minor crustal plates that make up the oceans’ floors and the continental land masses. Continuing geophysical research is revealing more fine details.
These plates are in motion due to the injection of new crustal material (magma) at the seafloor. This activity occurs primarily along the mid-ocean ridge system. At 40,000 miles in length, it is the largest mountain chain on our planet. The system basically consists of two parallel ridges separated by a rift valley. It is in this valley that the new seafloor crust is being created. These places are called spreading centers. The fastest-growing plate segments can move as much as six inches per year—a very high speed in geological terms.