Biblical writers were fascinated by earthquakes, and referred to them often to make their point. An earthquake is a good image for cataclysmic times when "everything nailed down is coming loose." Earthquakes threaten our assumptions about the stability of life. We like to think of earth as rock solid, but sometimes the earth moves. Sometimes when people fear flying on a plane, they resort to the ancient Latin by saying, "Just get me back to terra firma." We expect the ground to be firm. We want our buildings tied to the bedrock because our foundations need to tie to something that won't move. 

We are easily lured into thinking the same about our lives. We expect stability. We expect our lives to be "rock solid," but then something traumatic happens and "everything nailed down is coming loose."