13. Sinkholes—Buried Alive

These geological hazards have swallowed highways, apartment buildings, horses, camels, even golfers, with monster-size holes cracking the earth from Siberia to Louisiana. Filled with compelling eyewitness video of dramatic collapses, and following scientists as they explore the underlying forces behind these natural disasters, NOVA travels the globe to investigate what it's like to have your world vanish beneath your feet.