At 6:58 am on December 26, 2004, one of the most powerful earthquakes ever recorded began shaking the Pacific seafloor about 150 miles off the west coast of the Indonesian island of Sumatra. Within moments, the magnitude 9.0 quake gave birth to a tsunami — a wall of fast-moving water that is one of the most feared of all natural disasters.

The word tsunami comes from two Japanese words: tsu, which means harbor, and nami, which means wave. In English, tsunamis are often called tidal waves, but they have nothing to do with the tide. As NATURE’s Violent Hawaii shows, tsumanis are formed when an earthquake, landslide, or even the impact of a meteorite displaces huge amounts of water, sending it rolling at speeds of more than 500 miles per hour across the open ocean. As the tsunami travels into shallower water, near coasts, it slows down and the sloping seafloor pushes the waves upward — resulting in waves that can be several hundred feet high. The powerful flood waters can wash far inland, sweeping everything in their path back out to sea.

The effects can be devastating, as the Indian Ocean tsunami showed. Within hours of the initial earthquake, shorelines thousands of miles away were pummeled by waves as high as 30 feet. Fishermen, tourists, and coastal residents in Indonesia, Sri Lanka, India, Thailand, the Maldives, and even as far away as Somalia had little inkling of what was coming due to the speed of the wave and, more importantly, the lack of a tsunami warning system in the Indian Ocean. At last count, more than 155,000 people have been killed and more than 1.7 million displaced in what is being called one of the worst natural disasters of the last 100 years.

Hawaii was hit by a devastating tsunami in 1946 (shown above) and in 1960.

The Indian Ocean tsunami has also served to remind us of past tsunamis. In Alaska and Hawaii, people recalled the 9.2 trembler that hit Alaska’s Prince William Sound in 1964, sending a powerful tsunami barreling across the North Pacific. More than 100 people were killed in Alaska, California, and Oregon.

In 1960, a giant quake struck near Chile, hurling tsunami swells of up to 75 feet high against the country’s coastline. The floodwaters penetrated more than a quarter-of-a-mile inland and at least 200 people died. But the worst wasn’t over. The tsunami raced outward from the quake site, crossing the Pacific at jetliner speeds. Six thousand miles away in Hawaii, officials began to broadcast warnings that the tsunami was due around midnight. It struck hardest at Hilo, where a 35-foot wall of water snuffed out a power plant and swept away more than 60 people. Overall, up to 3,000 people died along the Pacific Rim that day.

Prior to the Indian Ocean tsunami, the most recent devastating tsunami struck Papua New Guinea on July 17, 1998. Sparked by a magnitude 7.1 earthquake that struck off the coast, it sent 30-foot waves crashing into seaside villages, killing more than 2,000 people. Papua New Guinea, like Indonesia, is within the “Ring of Fire,” an area in the Pacific Ocean where earthquakes are almost a daily occurrence.

Today, partly as a result of these historic disasters, some nations have established a tsunami warning system monitoring the Pacific Ocean. It is activated within moments of a potentially dangerous earthquake or landslide. Several countries affected by the 2004 tsunami are now working on a system for the Indian Ocean. Although the Pacific Ocean warning system has saved many lives, tsunamis remain difficult to predict, in part because the seafloor’s topography can steer them in surprising ways. Tsunamis are one of nature’s least predictable and most dangerous events.

This program premiered on November 13, 2005.

We’ve all heard them: the tales of dogs barking before the big earthquake hit; wildlife behaving strangely before the big hurricane; earthworms pouring out of the ground just before the big flood strikes.

Tall tales … or true?

Researchers say it’s probably a little bit of both. Plenty of studies have shown that some animals can sense major changes in the weather. Worms, for instance, are known to flee rising groundwater. Birds are known to be sensitive to air pressure changes, and often hunker down before a big storm. And in Florida, researchers studying tagged sharks say they flee to deeper water just before a big hurricane arrives. They also may be sensing the air and water pressure changes caused by the big storm.

Geologist Jim Berkland claims to have a formula that uses animal behavior to accurately forecast earthquakes.

“I think these animals are more attuned to their environment than we give them credit for,” Michelle Heupel, a scientist at the Mote Marine Laboratory who worked on the shark study, has told reporters. “When things change, they may not understand why it’s happening, but the change itself may trigger some instinct to move to an area that is safer for them.”

But can your kitty or puppy give you a cue that a big quake is coming? Researchers are skeptical. After years of study, the U.S. Geological Survey has this to say: “Changes in animal behavior cannot be used to predict earthquakes. Even though there have been documented cases of unusual animal behavior prior to earthquakes, a reproducible connection between a specific behavior and the occurrence of an earthquake has not been made. Animals change their behavior for many reasons and given that an earthquake can shake millions of people, it is likely that a few of their pets will, by chance, be acting strangely before an earthquake.”

What about other animal trends? In NATURE’s Can Animals Predict Disaster?, for instance, one geologist says he sees an increasing number of missing pets documented in the local classified ads just before an earthquake strikes in California. He, in fact, predicted the famous San Francisco earthquake of 1989. The theory is that the animals are fleeing the impending quake.

Again, other scientists doubt this. USGS scientists, for instance, say even simple science fair projects will show little statistical association. (See Do Lost Pet Ads Predict Earthquakes?)

Similarly, scientists are skeptical that any special “sixth sense” helped animals survive the great tsunami that swept the Indian Ocean in 2004. After the wave, people reported seeing animals fleeing to forests on high ground and finding few bodies of dead animals. But scientists note that little hard data exists, and that many animals may have survived simply because they are strong swimmers or able to scamper up trees.

Still, researchers like Liz Von Muggenthaler — who appears in NATURE’s Can Animals Predict Disaster? — believe animals can pick up the “infrasonic” sound pulses created by storms and earthquakes, and get a head start on fleeing to safety. It would make sense, she says, that the animals learn to associate such signals with danger.

But we should be careful not to give animals super-powers, says Whit Gibbons, an ecologist at the University of Georgia. “I always like stories of animals outsmarting humans, [but] I really don’t think animals have any special powers beyond those that help them in their daily lives,” writes Gibbons. “I do not doubt that many animals detect certain natural signals, such as the early tremblings of an earthquake, long before humans. This means they have opportunity to react before we can. But to think they are reacting any differently from someone who runs for an exit at a shout of ‘fire’ is to give wildlife more credit than is deserved.”

“As far as running inland to get away from a tsunami, I think an antelope, flamingo, or any other fast animal would probably do so because that’s where the forests are. Feeling a trembling earth, even if minutes before we would feel it, would not give much guidance to a running or flying animal other than a response to seek safety. The woods are the safest place for most animals, so when they flee from a shoreline they go inland, which means not only woods but higher ground. Completely natural and not at all mystical.”

Bill Barklow, a researcher who appears in this week’s NATURE, also believes animals aren’t specially adapted to avoid disaster. “I think it’s really unlikely that hippos or any animal has evolved behavior to avoid tsunamis specifically,” he says. “When they hear these infrasonic sounds that are produced by earthquakes, which happen very infrequently, they probably are just terrified of that very deep, heavy sound coming from a wide angle distant area and they just want to get out of there. So there’s a secondary benefit here. They haven’t evolved an escape behavior for tsunamis, but they are responding to infrasound, which has evolved for communication purposes.”

Did the elephant know the deadly wave was coming?

That’s the question explored by NATURE’s Can Animals Predict Disaster?

In interviews with scientists and eyewitnesses, NATURE probes the evidence that some animals may have senses that allow them to predict impending natural disasters long before we can.

Some creatures, for instance, may be able to “hear” infrasound, — sounds produced by natural phenomena, including earthquakes, volcanoes, and storms, that are inaudible to the human ear. This ability may give elephants and other animals enough time to react and flee to safety.

Another explanation may lie in animals’ sensitivities to electromagnetic field variations. Quantum geophysicist Motoji Ikeya has found that certain animals react to changes in electrical currents. He now regularly monitors a catfish, the most sensitive of the creatures he has tested, to aid him in warning others of coming disaster.

Follow NATURE as it reexamines ancient ideas about how animals can predict disaster which are now gaining credence in scientific circles.

To order a copy of Can Animals Predict Disaster?, visit the NATURE Shop.

Online content for Can Animals Predict Disaster? was originally posted November 2005.

It is one of the most beloved stories in the Bible and many other great religious texts. God, upset by the behavior of his creations on Earth, decides to start over — to wipe the slate clean by sending a great flood to wash away “both man and beast, and the creeping thing and the fowls of the air.

But at the last moment, God decides to spare the family of one good man. And he orders this man — named Noah in the Bible — on an extraordinary search and rescue mission: He must build an ark, a sort of giant life boat, and pack it with “two of all living creatures, male and female.” When the great flood recedes, Noah and his oceangoing menagerie are left high and dry on the side of a great mountain, free to renew life on a barren landscape.

To some, the story of Noah is an ancient metaphor for the restoration of life after a great disaster. But to others, it is history, or as they say in Hollywood: “Based on a true life story.” And for centuries, these true believers have searched for Noah’s landing place and the remains of his ark on the rocky, snowy ridges of the Holy Land’s highest mountains.

Much of the attention has focused on Mount Ararat, a 17,000-foot-high extinct volcano in Turkey, near its borders with Iran, Iraq, and Armenia. Even in the 13th century, Ararat already had a reputation as Noah’s final destination. And in the famous TRAVELS BY MARCO POLO, the Venetian adventurer describes its imposing grandeur: “It is so wide that it takes more than two days to circle it. The summit’s snows are so deep year round that one can never climb it.”

Such grueling conditions, however, haven’t prevented explorers from scrambling up Ararat’s slopes in search of the Ark. In modern times, these quests have become increasingly high-tech, using aerial photography and ground-sensing radars to probe the mountain’s thick ice sheets and rock fields. Others have seized on images captured by satellites orbiting high above the earth. Every shadow, snow bulge, and oddly-shaped rock is scrutinized for the possibility that it, at last, is the remains of the ark.

Some have claimed great discoveries — bits of the ark’s wood, or photographs of its decaying hull — only to fail to produce convincing evidence. Others have admitted to perpetrating hoaxes, either for personal publicity or to embarrass those they say are engaged in a ridiculous quest. Skeptics, for instance, question how Noah’s great wooden hull would have survived some 3,000 years exposed to the harsh elements.

Such challenges haven’t stopped the speculation, however. Ark enthusiasts continue to search religious texts for clues to the Ark’s location, debating the merits of different mountains. Others try to tease out the great ship’s exact design, even building scale models that they have tested in wave tanks. (Their conclusion: a rectangular ark the size of a modern cargo ship would have surfed the flood’s giant waves with aplomb, although the animals would have gotten pretty seasick.)

Others ponder Noah’s construction techniques and strategies for rounding up the animals, food, and necessary construction supplies. Some have even done precise calculations of how many animals were on board, how much food they needed, and how much space they occupied. A few even mount expeditions — no mean feat given that the areas they visit are often plagued by violence.

Meanwhile, some geologists wonder whether new evidence of great floods that swept parts of the Black Sea basin thousands of years ago may have given rise to the story of Noah’s Ark. And archeologists who have studied ancient sunken towns voice similar ideas. So far, however, there is little consensus beyond the idea that the story of Noah’s Ark is one of the best ever told.

Still, some nations in the historic Holy Land are beginning to develop another kind of ark: an extensive system of nature reserves where threatened species can be protected from the flood of humanity. Like the great lifeboat of yore, these shelters may yet deliver survivors from the storm.