Sinkholes: Swallowed Alive

Massive sinkholes devour entire city blocks with no warning. A woman falls through the ground in her backyard and is nearly buried alive. Sinkholes can happen anywhere and to anyone. In this special, Nat Geo breaks down the science of sinkholes — telling harrowing stories of survival and taking viewers on a hair-raising journey through an underwater cave system to better understand what causes these terrifying freaks of nature. (Source: National Geographic Channel)