Seven Deadly Disasters

In the wake of December's indonesian tsunami, what does mother nature have in store for us next?

Richard Alley is a geologist at Penn State University. In his office he has a graph that shows the earth's climatic history for the past 100,000 years. The graph reveals that for the first 92,000 of those the global thermometer roller coastered in and out of ice ages and hot spells. The turmoil leveled off about 8,000 years ago into a period of anomalous calm, one that's still with us. "The chart goes boing-boing-boing-boing-hmmmm," says Alley. "We live in the hmmmm." And because human civilization coincides with, and perhaps results from, this remarkable period of calm, most of us are blissfully unaware of the fire and ice that nature can throw at us. "We think it's always going to be hmmmm," says Alley, "but it's not."

As it happens, during the past 8,000 years humanity has also generally been spared the grand-scale natural cataclysms to which the earth is heir: the mega-volcanoes, the perfect earthquakes, the species-extinguishing meteors. Last December, when mother earth cracked her back and launched an Indian Ocean tsunami that killed nearly 100 times more people than died in the 9/11 attacks, the world was shocked. Such disasters seemed passé, the types of things that could now be found only in history books and at Hollywood pitch meetings. But we should have known better: Though cataclysmic from a human perspective, the earthquake-tsunami combo is a geological cheeseburger and Coke. Calamities, scientists tell us, happen all the time. Here are seven that could hit tomorrow. Of course, odds are none of them will, but if any of us are around in 75,000 years we'll most certainly have seen them all.

The Great Atlantic Tsunami

As awful as last winter's Indian Ocean tsunami was, there is a worse scenario, in which 160-foot waves slam into the Atlantic seaboard between New York and Miami at speeds of 560 miles an hour. This may seem far-fetched; tsunamis, after all, are caused by the plates of the earth grinding against one another, and the plates under the Atlantic are fairly sedate. (Last December's earthquake involved 780 miles of underwater fault line, says Costas Synolakis, a tsunami scientist at the University of Southern California. Some areas of the seafloor jerked 30 feet, displacing an amount of water 10 times that of the Great Salt Lake.)

An Atlantic tsunami, however, would have nothing to do with plates. A group of scientists, most notably Bill McGuire of University College London, are alarmed by a half-trillion-ton mass of rock slowly sliding off the side of the Cumbre Vieja volcano on the Canary island of La Palma. Should Cumbre Vieja experience a major eruption (as it last did in 1949), its face would almost surely collapse, shaking the mega-boulder loose. Once it splashed into the water, McGuire envisions, it would be like a mammoth pebble landing in a lake, sending titanic ripples across the Atlantic that would clobber North America and treat Africa and Portugal even worse. (Remember, only the Pacific currently has a tsunami warning system.)

Most tsunami scientists think the likelihood of this chain of events is remote; some even believe McGuire has acted irresponsibly for shopping the scenario to the media. Landslides of the size required are extremely rare, and as a Tsunami Society press release puts it, "No such event--a mega-tsunami--has occurred in the Atlantic Ocean in recorded history. None."

The problem with that disclaimer, according to Steven Ward, a geologist at the University of California at Santa Cruz, is that recorded history is little more than a blip. Moreover, our knowledge of tsunamis is limited. Unlike earthquakes, tsunamis are rare and leave precious little geological evidence; tsunami scientists are still arguing about how earthquakes and landslides generate these killer waves.

The upshot is that there's considerable disagreement about what a La Palma collapse would mean. One school of thought is that waves wouldn't increase by more than a mere meter or so, not even enough to affect surfing. Even Ward's calculations are vastly different from McGuire's. He envisions waves only 60 feet high--not enough to clobber Manhattan but just enough to submerge everything below the fourth floor.

America's Big One

December's Indonesian earthquake was the second deadliest in history, though the vast majority of deaths were from the resultant tsunami. The deadliest earthquake on record, which occurred on January 23, 1556 in Shanxi, China, killed 830,000 people without the help of mega-waves. Geologists estimate that the quake was a magnitude 8, only one tenth as seismically intense as the underwater Indonesian quake last year. (The Richter scale is logarithmic: Each number represents a tenfold increase in measured amplitude, so a magnitude 9 earthquake has 10 times greater amplitude than an 8. The actual energy released by a magnitude 9 earthquake, however, is 32 times greater than that released by an 8.)

For decades Americans have been waiting for a huge earthquake to strike a major California city. October 1989's magnitude 6.9 quake outside San Francisco, which killed 63 people, and 1994's magnitude 6.7 quake outside Los Angeles, which killed 60, were pretty bad. If their epicenters had been closer to their respective big cities, the damage could have been catastrophic. Currently the U.S. Geological Survey puts the odds of a major earthquake--6.7 or higher--directly striking the San Francisco Bay Area within the next 25 years at 70 percent. In other words, it's more likely to happen than not.

According to projections by geophysicist George Pararas-Carayannis, co-founder of the International Hazards Society, a repeat of the 7.8 magnitude quake that upturned San Francisco in 1906--a quake whose epicenter was right under San Francisco, unlike the one in 1989, which was more than 50 miles away--would kill between 3,000 and 12,000 people. Much would depend on the time of day the earthquake hit; the damage at night, when people are asleep, would likely be less than during rush hour, when people are in concrete office buildings or on roadways. Either way, it could cause tens of billions of dollars in damage and render as many as 150,000 residences uninhabitable. A similar-size quake under Los Angeles could have comparable results.

California isn't the only vulnerable area in the United States. The USGS earthquake hazard map (eqhazmaps.usgs.gov) shows a glowing hot spot that stretches northeast from Memphis through the New Madrid and Wabash Valley seismic zones, almost all the way to Indianapolis. Although the region doesn't lie near plate boundaries, the plate it sits on is cracked and strained. Scientists think the plate almost split when the super-continents were breaking, and now it's pretty fragile.

Three jumbo quakes struck the area between December 1811 and February 1812. Each had a magnitude of 8 or higher; just about every structure around the epicenter of New Madrid, Missouri was damaged or destroyed. Fortunately what was a bad winter for tepees and log cabins probably wasn't so costly in human life. The next one will shake Memphis, Nashville, St. Louis, Little Rock and possibly Indianapolis. The USGS estimates that within the next 50 years there is a 10 percent chance of a repeat of the 1811 quake and a 90 percent chance of a smaller quake, say a 6.

While modem quake activity in this region is rare, the likelihood of damage is as high as in California. One reason is that many buildings and roads in the Midwest aren't built for shaking. Building codes in common earthquake places such as Tokyo and Los Angeles lessen the damage; the Midwest hasn't taken as many precautions, meaning many more buildings will crumble and many more lives will be lost. Another reason damage will be great is the terrain itself. It's composed of rich, thick sediments that propagate earthquake shaking far and wide. Consider that the 1906 San Francisco temblor was felt 350 miles away in Nevada, but the 1811 New Madrid quake rang church bells in Boston, 1,000 miles away.

Killer Lakes

On the morning of August 22, 1986 a traveler approached the villages near Lake Nyos in a remote region of Cameroon. What he found was horrifying. Everything--every human, every cow, every dog--was dead. He alerted the authorities, who found more than 1,800 humans and thousands of animals lying dead, none with an apparent injury. Whatever had killed them had struck swiftly: One woman fell under her clothesline, a wooden pin still in hand. Most of the deaths were near the lake, but many were down in the valleys below it, the farthest victims 14 miles away.

Amid rumors of alien invasion, Western scientists were brought in. "There was no record of this before. It was bizarre," says USGS research chemist Bill Evans, one of the investigators.

The culprit turned out to be the lake itself. "Nyos is 700 feet deep and fairly narrow," Evans explains. "It's a meromictic lake," meaning its water doesn't mix vertically. The bottom of the lake is connected to a deep-earth magma source. The magma leaks carbon dioxide into the bottom of the lake at a regular rate, but because the lake is meromictic, the CO2 builds up at the bottom and stays there, dissolving into the water the way CO2 dissolves in champagne. On the evening of August 21 something happened--most likely a nearby landslide--that shook the lake, disturbing the giant cloud of CO2 and causing it to rush to the surface. Because CO2 is heavier than air, it pushed the oxygen-rich air up from the ground and away from the mammals who required it. Within a few gasping breaths, the entire village was wiped out. The CO2 cloud floated down the valleys, suffocating everything in its path before it finally dissipated.

Nyos is highly unusual; few lakes both are meromictic and have a CO2 source at the bottom. Evans and his colleagues searched for others. While they didn't find many, they did find one of enormous concern: Lake Kivu, which is on the border of Rwanda and the Democratic Republic of the Congo and is about the size of Lake Tahoe. The good news is that Kivu is a more stable lake than Nyos; it would take an eruption from the magma to disturb the CO2. The bad news: About 2 million people live around that lake.

Lake Nyos is now regularly degassed. Kivu could be too, but Evans's warnings have gone unheeded by governments enmeshed in civil strife.

The Next Dust Bowl

Regardless of whether humans are forcing the climate to change, the climate likes to change on its own. Lately, for reasons climatologists are still trying to understand, the West Coast has been deluged with rain. Las Vegas's rainfall in January and February was equal to its annual average; wildflowers are blooming in Death Valley. Meanwhile the Northeast has endured three especially cold winters.

Now, cold is okay for a while, and extra rain usually isn't a problem. But in other parts of the world, the opposite--a drought--could take hold at any minute. The dust bowl of the 1930s and the Sahelian (sub-Saharan) drought of the 1970s and 1980s that killed more than 1.2 million people are seared in our memory.

But these droughts are hardly worst-case scenarios. "The climate can change within a year or two in a given area and completely alter the ecosystem--from wet to dry, from hot to cold--and render our buildings, our agriculture, our way of life inappropriate to the climate very quickly," says Penn State's Alley, who recently served as chairman of a National Academy of Sciences study on abrupt climate change. He worries about the American Great Plains plunging into a drought that could last a century. "It has happened in the American Middle West several times in the past few thousand years," he says, basing his conclusions on fossils, studies of tree rings in the Dakotas and core samples of soil from lake beds. "These 100-year droughts make the Grapes of Wrath dust bowl look like a blip."

Were Alley's worries to be realized, soil would turn to dust, the Mississippi would diminish, and states would fight one another for water from the Rockies. If it got bad enough, people would abandon the center of the nation and flock to the coasts. We'll weather the crisis by buying food from overseas if the country is in sound financial shape. If not, tens of thousands will starve. Remember, the difference between the hardships of the American dust bowl and the 1.2 million deaths of the Sahelian drought was not the severity of the climates but the resiliency of the economies involved.

Vesuvius, USA

Volcanic disasters come in two flavors: bad and really bad. An example of a bad one is Mount Pelée on the Caribbean island of Martinique. In 1902 an avalanche of fiery rock slammed into the town of St. Pierre at 80 miles an hour and killed 28,000 people.

A really bad eruption could be thousands of times worse. For example, 2.1 million years ago a hot spot of magma burst through the earth's crust near what is now Wyoming's Yellowstone National Park and ejected 600 cubic miles--yes, that's cubic miles--of rock. It landed as far away as Iowa.

U.S. geologists are now concerned about Mount Rainier, a dormant volcano just outside Seattle. Rainier's biggest threat isn't an explosive eruption but a giant lahar, or mud slide. Lahars are common on volcanoes, even on dormant ones, because the acidic gases inside weaken the structure of the rock on the side of the mountain. After a big rainfall whole chunks of volcano can liquefy like wet concrete, resulting in 40-foot-high walls of Slurpee flowing through valleys at 20 miles an hour. Small lahars slide off Rainier regularly, large ones every few hundred years. About 5,600 years ago a huge lahar called the Osceola Mud-flow paved more than 212 square miles of what is now suburban Seattle and Tacoma, a region that today has a population of more than 100,000. A warning system has been set up, but if another Osceola flow comes sloshing down the mountain, there won't be enough time, nor enough high ground, for 100,000 people to escape.

Scientists are also keeping an eye on Yellowstone--yes, our lovely national park sits atop a volcano. It has been dormant, but dormant doesn't mean dead. Yellowstone first erupted on a really bad scale 2.1 million years ago, then again 1.3 million years ago, then about 640,000 years ago. "If we're on a roughly 700,000-year cycle," says John Valley, a geologist at the University of Wisconsin, "we're just about due for the next one."

We hope these eruptions are like Rocky movies, each weaker than the one before. If not, the next eruption could cause deaths in the millions. "Each of the last three eruptions covered everything west of the Mississippi," reminds Valley. The residents of Wyoming, Idaho and Montana would suffocate instantly, and their bodies would be incinerated by scorching ash and gas. Throughout the Midwest and Rockies, incandescent stones would fall from the sky, forests(concluded on page 74)Disasters(continued from page 66) and fields would burn, and the air would be filled with unbreathable ash.

This disaster, thankfully, is unlikely to happen on our watch. The USGS maintains the Yellowstone Volcano Observatory to monitor seismic and magmatic activity underneath the park. According to the observatory's director, Jake Lowenstern, there's no need to panic. "We have no indication whatsoever that this is getting active again," he says. Moreover, new activity will likely indicate a smaller volcanic event, of which Yellowstone has had thousands over the past 2 million years. "It's just not likely to be catastrophic," says Lowenstern. "My job often is to calm people down."

The Modern Plague

Unlike geologists, who feel they have to downplay potential dangers, epidemiologists--scientists who study how diseases spread--feel as if they're screaming and no one is listening. "We at the World Health Organization believe the world is now in the gravest possible danger of a pandemic," Dr. Shigeru Omi announced at a conference on the Asian bird flu in Ho Chi Minh City in February. Gravest possible danger, eh? Mario quitting American Idol got bigger play.

The influenza virus is a tiny germ that attacks the respiratory system and usually threatens no one but the aged and ailing. But viruses evolve, mutating constantly as they circulate through animal hosts and pick up new genes. Every few decades a strain emerges with the three qualities needed to create a pandemic, or a global epidemic: First, it is deadly. Second, it is easily transmitted between humans, such as through a handshake or sneezing. Third, it is something our immune systems have never seen and have no defenses against.

In 1918 the so-called Spanish flu virus scored this hat trick. It spread around the world in two months and killed 500,000 in the United States (more than the U.S. lost in battle in World War I) and an estimated 50 million worldwide.

Omi and his colleagues at the WHO are worried about a relatively new strain of flu virus called H5N1, which is devastating chickens in Asia. This isn't bad news just for fans of moo goo gai pan. The virus has already met two of the three critical criteria: It's deadly and novel. Of the 55 humans who've contracted the disease, 42 of them have died, an incredibly high death rate.

The third leg of the stool--human-to-human transmission--is only a mutation away. The virus merely has to pick up another gene, perhaps from a pig virus (pig respiratory diseases are remarkably similar to human ones) and--voilá--a mercilessly efficient killer of human beings will be on the loose. While the WHO and the U.S. Centers for Disease Control and Prevention are working hard to contain the virus in Asia, the task is tough. The 1918 flu circled the globe before commercial air travel. Today, when one can fly from Hong Kong to New York nonstop, the virus can spread faster than we can detect it.

The CDC is developing a bird-flu vaccine that could save hundreds of thousands of lives in a pandemic. But only nine countries can produce vaccines. It's unlikely they'll be able to produce enough to inoculate all their own citizens and extremely unlikely they'll distribute the vaccine beyond their borders.

Space Killers

There's an inverse relationship between the severity of a disaster and its frequency. The worse the potential event, the less likely it is to hit tomorrow. With the exception of the pandemic, the catastrophes that cost many millions of lives occur only in many-thousand-year intervals. Which prompts the question: In the 4 billion years this planet has remaining before a dying sun engulfs it, what's the worst that can happen?

The answer: It can get slammed by a comet or an asteroid several miles wide. According to die calculations of University of Arizona geoscientist Henry Melosh, that impact would hit with the energy of 100 million megatons of TNT. It would send millions of cubic miles of rock into the sky; the rock would fall back to the earth in the form of a trillion meteors, which would heat the atmosphere to 450 degrees.

In reality, comets aren't a major threat, since they spend most of their time way out beyond the orbit of Neptune. But from time to time they roar toward the sun. Comet Hale-Bopp majestically sailed past in 1997, coming just inside Earth's orbit. And sometimes one even collides with a planet, as when comet Shoemaker-Levy 9 plunged spectacularly into Jupiter in 1994.

But Jupiter is a much bigger target, as well as a heavier one that pulls in comets gravitationally. The chances of a comet hitting our tiny planet are "close to zero," says Erik Asphaug, a planetary scientist at the University of California at Santa Cruz, who says scientists had a hard time calculating the risk of this event. "We assess hazards by multiplying die likelihood of the event with the destruction it would cause. How do you multiply a likelihood of zero times a destruction of infinity?" Still, in the extremely unlikely event that something on the order of the 25-mile-long Hale-Bopp arrived in your mailbox at a speed of 30 miles a second, Asphaug assures us, "there would be no living thing left on earth except those bacteria that can live deep underground in the rocks."

Asphaug can be reasonably sure of this because a much smaller body, the six-mile-wide KT asteroid, slammed into the Yucatán peninsula 65 million years ago and presumably broiled all surface creatures to death, most notably the dinosaurs.

Let us pause momentarily to appreciate a small irony: Nature's destruction is also always creative. The sort of asteroid we think might destroy us is in fact the very thing that gave us life. At the time the KT asteroid struck, the first mammal species--small, weak and scared--were hiding from the mighty dinos. The smart ones ceded the surface to the ferocious reptiles and adopted a burrowing lifestyle. These gopherish forebears were therefore shielded from the asteroid-induced inferno, survived and eventually took over the planet.

We still have an edge, having developed technology that will allow us to spot these asteroids long before they hit. Already our telescopes have found all the near-earth objects (NEOs in astronomical parlance) wider than six miles, and we're developing a new telescope that promises to find all NEOs down to 300 yards in size. (Objects smaller than 300 yards could still surprise us with as much as a 1,600-megaton explosion and be a regional superdisaster, but meteors that small don't threaten extinction.) Says Asphaug, "Within 10 years we'll know all the NEOs down to one kilometer," roughly 0.6 miles.

At this point we know of nothing on a course to hit us. But what if something starts heading our way? "We'll have a lot of time, probably hundreds of years before impact, to figure out how to deflect it," Asphaug maintains.

The solution we adopt could be far simpler than the nukes Bruce Willis uses in Armageddon. "You probably just have to go up there and paint the thing white," Asphaug contends. "With the increased reflectivity, the sun's photons would change its course in time."

That's a relief. Now someone has to figure out how to pull that white-paint trick on the viruses.

The new strain of bird-flu virus is incredibly lethal: Of the 55 humans who've become sick, 42 have died.