MEXICO'S MANY PLATE TECTONICS

    Mexico is located on one of earths subduction zones, where the ocean floor of the Cocos tectonic plate is sub-ducting beneath the continental plate of the north american plate. Subduction zones get earthquakes and sometimes they stick together (locking), the lower plate pulling the upper plate down with it and therefore causing stress to build up. When the stress builds up to the breaking point, the upper plate breaks free and springs back to where it was before. The lower plate moves very slowly, only around 6 cm per year which is as fast as finger nails grow. It takes many hundreds of years for stress to build up before causing a large earthquake.

      Most of Mexico is on the north american plate but is also on several other plates. The Baja California Peninsula is on the gigantic pacific plate, which is moving northwest and under the north american plate. The intersection of these plates under the Gulf of California causes parallel faults which are part of the famous San Andreas Fault system.
     The small Rivera plate, between Puerto Vallorta and the southern tip of Baja California is moving in a southeast direction and rubbing against the pacific plate  it is also moving under the north american plate. The Coco's plate and tiny Orozco plate are ocean crust plates located off the south coast of Mexico. The collision of the Coco's plate and the north american plate had caused the disastrous 1985 earthquakes. ( Mexico is one of the most seismological active regions on earth. The motion of these plates causes earthquakes and volcanic activity.) Mexico is being carried northwest by the Coco's plate. The ocean floor is fairly dense, when it strikes the lighter granite of the Mexican land mass, the ocean floor id forced under the land mass, creating the deep middle american trench that is at Mexico's southern coast.
         The westward moving land a top the north american plate is slowed and crumpled where it meets the Coco's plate, creating the mountain ranges of southern Mexico. The subduction of the Coco's plate accounts for the frequency of earthquakes near mexico's southern coast. As the rocks on the ocean floor are forced down, they melt and the molten material is forced up through weaknesses in the surface rock, creating the volcanoes in the cordillera Neovalcanica across central Mexico. Motion along the San Andreas Fault in the past pulled Baja California away from the coast, creating the Gulf of California. Continued motion along this fault is the source of earthquakes in western Mexico. September 1985 Mexico city was hit with a Richter scale of 8.1 magnitude earthquake from the subduction zone off Accpulco and killed 4,000 people in the city and Volcan de Calima, south of Guadalajara, erupted in 1994.