pressure build-up, it is likely to erupt in the not too distant future. And it has happened in the past. Geologists have discovered evidence of a massive tsunami that struck the Pacific Northwest in 1700 -- as powerful as the devastating Indian Ocean Tsunami of 2004. Hundreds of thousands of lives are at stake. Emergency planners, seismologists and other researchers are trying to get a handle on when Cascadia will blow, what it will look like and what - if anything -we can do to minimize the disaster.

WWhat happens when the most intense tornado ever measured strikes Dallas, Texas? With winds clocked at 318 miles per hour, the monster twister carves a path through the city up to a mile wide. It happened once before, just two hundred miles to the north in Oklahoma City. There in May 1999 a "Megatornado" scoured the earth for 85 minutes along a 38-mile path. 43 people died and property damage was enormous. It became history's first billion-dollar tornado. But in more-densely developed Dallas, the scenario is worse: as many as a thousand dead... and FIVE billion dollars in damage.

What would happen if a category 3 hurricane were to hit New York City? With an awesomely high storm surge and intense winds attacking one of the most heavily populated and economically vital locations in the world, the potential for massive destruction is almost unprecedented. We explore the less-known but extensive history of previous northeast hurricanes -- especially the "Great Hurricane" of 1938 -- in order to create empirical evidence that a storm of this size is not a science fiction movie but a very real possibility in the near future. Time is also taken to explore the scientific nature and origins of hurricanes and to get an overview of some of the scientific and engineering changes that are taking place in the field of hurricane damage prevention. Using computer animation, models and re-creations the story concludes with a jaw-dropping view of what a storm like this might look like from inside the Big Apple.

Examine the cataclysmic earthquake that struck San Francisco on April 18, 1906, and discover how the city's rush to get back in business came at a price.

The San Andreas Fault runs roughly 800 miles through some of the most valuable real estate in the world. The southern section hasn't had a significant quake for over 300 years and is primed and ready for another big one.

Inflicting over $80 billion in damage and causing the deaths of over 1800 people, Hurricane Katrina was among the greatest engineering disasters in US history. But was Katrina really the "big one" New Orleans had been waiting for?