America's Next Top Disasters
Ranking determined by likelihood and potential impact
1. Levee Failure in the Sacramento Delta
2. Flooding in the Upper Mississippi
3. Indian Point Meltdown
4. Earthquake in Missouri
5. Eruption at Yellowstone
6. Tornadoes in Dallas
7. Landslide at Mount Rainier
8. Tsunami on the Eastern Seaboard
9. Massive Power Failure in Boston
10. Rupture in the Alaska Oil Pipeline

Rupture in the Alaska Oil Pipeline

The Alaska pipeline was built to withstand everything its designers could think of. But the supports for the pipeline are anchored in permafrost, which is now melting. Up to a third of the uprights are out of alignment, and more will be at risk if the thaw continues. A pipeline break would jeopardize 1 billion barrels of oil per day - 17 percent of the nation's capacity.

Likelihood: Low. (Admitting you have a problem is the first step to fixing it.)

People affected: Entire US population, potentially

Landslide at Mount Rainier

According to the US Geological Survey, Mount Rainier presents the "greatest volcanic hazard" in the Cascade Range because there are so many people in its shadow. The USGS says an eruption could melt Rainier's glacier, sending rivers of volcanic mud and ash - a moving wall of cement - toward Puget Sound.

Likelihood: Medium. Such slides occur once or twice a millennium. It's been 550 years since the last one.

People affected: 2.4 million

Eruption at Yellowstone

Yellowstone's pretty geysers and hot springs are powered by one of the world's most active volcanic systems. Previous eruptions buried most of North America - really - from Arkansas to Oregon, Canada to Mexico. The next one could do the same.

Likelihood: Low. But not zero.

People affected: Depending on the size of the eruption, anywhere from tens to hundreds of millions

Levee Failure in the Sacramento Delta

Next to New Orleans, the capital of California is more dependent on levees than any other US city. Built on the banks of a river, most of Sacramento is 15 to 20 feet below water level. According to UC Davis geologist Jeffrey Mount, there's a better-than-even chance that the levees will fail by midcentury, jeopardizing the water supply of 22 million Americans.

Likelihood: High. 66 percent in the next 50 years.

People affected: 22 million

Flooding in the Upper Mississippi

When you try to contain a river, you're bound to spill some. The very qualities that made the banks of the Mississippi the perfect place to start a village also make it the worst place to build anything permanent. The river produces spectacular floods about once every 20 years, no matter what we do to stop it.

Likelihood: High. The last great floods were in 1993, so we're coming due.

People affected: 72 million - everyone in the Mississippi floodplain

Tornadoes in Dallas

The National Weather Service is worried about a tornado cluster over Dallas at rush hour. The fear: A big twister traps 87,000 people in their cars and causes nearly $3 billion in property damage, making it the one of the most destructive tornadoes in US history.

Likelihood: Medium. Dallas has dodged the bullet. So far.

People affected: 5.7 million

Masssive Power Failure in Boston

A dearth of new power plants combined with a growing population means that New England is poised for summer blackouts by 2008. A blackout caused by a heat wave, like the one that hit Chicago in 1995, would be wicked bad.

Likelihood: Medium. Depends on whether new power plants get built.

People affected: 14 million

Indian Point Meltdown

In the mid-1950s, it seemed like a good idea to have a nuclear reactor 35 miles from Manhattan. Now it doesn't. When sirens sound and the evacuation orders come, even the rich may not be able to leave, since half of New York City dwellers don't have access to a car.

Likelihood: Medium. There could be one accident in 600,000 years of operation, or it could happen tomorrow.

People affected: 21 million

Earthquake in Missouri

In 1811, New Madrid, Missouri, saw the most powerful earthquake ever recorded in the lower 48; it rang church bells as far away as Boston. A large temblor along the fault line would hit St. Louis and Memphis, which lack effective earthquake building codes.

Likelihood: High. 90 percent chance of a magnitude 6 or 7 quake in the next 50 years.

People affected: 3.7 million

Tsunami on the Eastern Seaboard

A small volcanic Canary Island called La Palma controls the fate of the East Coast. A 1949 eruption caused the western side of the island to slip a few yards into the Atlantic. In a future seismic event, the 500-billion-ton ridge could slide farther into the ocean, resulting in a mega-tsunami that would strike the East Coast.

Likelihood: Low. Might not happen for a few thousand years, if ever.

People affected: Everyone on the eastern seaboard