Scientists offer insight into how and where a 10.0 megaquake could strike. This two-hour special explores one of the most deadly and perplexing mysteries that surrounds planet earth: huge megaquakes.

Chicago is known as the "Windy City", but many believe a tornado can't strike a downtown filled with massive high-rise skyscrapers. It's a dangerous misconception. In 1967, a destructive high-speed tornado screamed along a 16-mile path through the south Chicago suburb of Oak Lawn and all the way to Lake Michigan. Had the path been just 10 miles to the north, the twister would have punched its way right into the Loop. The city's emergency officials say it bluntly: "Chicago is at high risk for tornadoes." In 1967, 33 people died. In the future, how many more will be at risk? Will the city's skyscrapers survive? It happened before, and it can happen again. We'll revisit the '67 disaster, restage it using state-of-the-art computer animation, and simulate how Chicago might hold up in the face of current catastrophe.

What would happen if a massive earthquake and tsunami were to strike the West Coast of the United States? Experts say it could easily match the catastrophic 2004 Indian Ocean tsunami in scale and might.

The largest volcanic eruption of the past two million years occurred on the Indonesian island of Sumatra, 75,000 years ago. The impact from the super volcano Toba decimated the local habitat.

In 1883, Krakatoa, the most famous and feared volcano on Earth, erupted. Gigantic explosions blew the volcano to bits, which triggered massive lava flows that generated huge tsunamis. Nearly 37,000 died, the greatest death toll caused by a volcanic eruption.

Hawaii, 1868. the volcano, Mauna Loa, in its most spectacular eruption, spewed out enough lava to cover 40 percent of the Big Island. A similar eruption occurred in 1950. Now that the island has become developed, the potential for damage and loss from a major eruption is astronomical. Small villages have been replaced by large tourist resorts and luxury homes. Using state-of-the-art computer animation, take a look at how an event similar to 1868 would impact Hawaii. Watch buildings crumble during large earthquakes, see homes and resorts destroyed by speeding lava, and what's left of the island drown under tsunamis and mudflows. Thousands of people could be dead, and the economy of this island paradise would be destroyed for years to come.

In this episode, a flaming tornado terrorizes a team of firefighters. A Hawaiian volcano wipes an island paradise off the map. And an avalanche of rocks and debris obliterate a village in Honduras.