Earthquakes are the results of two tectonic plates colliding each other; they are also a frequent occurrence in the Land of the Lost, a dimension that has similar but not identical traits with Earth.
Earthquakes occur when the Land of the Lost collides with a different dimension with different Marshalls. Rick and Will are able to stop the dimensions from colliding and everything goes back to normal (well as normal as it can get in the Land of the Lost). Although the fate of the other Marshalls is never discovered, another earthquake occurs when Rick Marshall attempts using one of the Pylons to return to home. His attempt results in the Great Cataclysm that devastates much of the Land of the Lost. Although Rick gets sent home, he strands Holly Marshall and Will Marshall behind without him, destroys High Bluff, separates Cha-ka from his family, opens a doorway that brings his brother Jack Marshall through and allow Lulu and Torchy to migrate into their area. As a result of these changes, Holly, Will and Jack have to move into an old temple as their new home.