Tsunamis are one of the most terrifying forces of nature, destroying all in their path. The December 26th Tsunami is estimated to have released the energy of 23,000 Hiroshima-type atomic bombs. What are the enormous forces that generate these catastrophic waves deep on the ocean floor? With 50% of the world's population living within a mile of the sea, this episode looks at what could happen in the future. East coast cities from New York to Miami face the threat of a truly colossal wave that could be generated by the collapse of an active volcano off the coast of Africa.