Earthquakes 

This theory is probably the least likely of all of the theories.  The two major factors that these theories rely upon are the present condition of the Classic-stage Mayan ruins and the frequency of earthquakes in the highlands of Guatemala. 
 

One of the main arguments that researchers use to disqualify this theory is the unlikeness that any entire region be abandoned due to a natural disaster.  We see that it is possible for an individual city to be abandoned but it is extremely unlikely that the whole country be abandoned.  After the Pompeii disaster Italy was not abandoned.  Another reason why this theory is highly unlikely is the fact that while earthquakes are extremely violent and strong in the highlands of Guatemala and Chiapas the Petan lowlands are far enough away from the earthquake belt that they do not experience earthquakes with the intensity of the highlands.  So what caused the damage to the Mayan ruins?  It is probably due to jungle growth or possibly earthquakes after the Classic period.