The current theory about earthquakes holds that they are caused by adjoining plates of rock sliding past each other; the plates are pressed together until powerful forces overcome the resistance. As plausible as this may sound, at least one thing remains mysterious on this theory. The overcoming of such resistance should create enormous amounts of heat. But so far no increases in temperature unrelated to weather have been detected following earthquakes. Which one of the following most accurately expresses the main point of the argument? ['No one will ever be sure what the true cause of earthquakes is.', 'The current theory does not fully explain earthquake data.', 'Contrary to the current theory, earthquakes are not caused by adjoining plates of rock sliding past one another.', 'No increases in temperature have been detected following earthquakes.']