Wave of Destruction

Emily Sohn

Jan. 19, 2005

It was a nightmare come true.

On Dec. 26, 2004, a huge wall of water rose from the Indian Ocean and slammed into the coasts of countries in Asia and Africa. The giant wave, called a tsunami, washed people out of their homes and swept them off beaches.

From Indonesia and Thailand to India and Somalia, the terrifying wave left more than 150,000 people dead. Millions lost their homes. It was one of the most deadly and destructive natural disasters in recent history.

The recent Indian Ocean tsunami caused extensive damage in many places, including the town of Meulaboh on the island of Sumatra, Indonesia. U.S. Navy photo by Photographer's Mate Airman Jordan R. Beesley

For the past few weeks, volunteer organizations and governments around the world have been rushing to help. Meanwhile, many scientists are looking at the disaster as a major wakeup call. Systems for detecting tsunamis and warning people that one is coming just aren't good enough in many places, critics say.

Scientists are now trying to find ways to do a better job of detecting tsunamis and providing timely warnings of danger.

Rare events

Tsunamis are a natural product of Earth's geology. They're caused by underwater earthquakes, volcanic eruptions, or landslides. There's no way to stop them from forming. And there's no way to know exactly when or where one will hit next.

The recent Indian Ocean tsunami not only killed people and damaged property but also caused environmental damage to marine ecosystems. National Oceanic and Atmospheric Administration

Tsunamis are also extremely rare. So, there's not a lot of data to work with. Instead, tsunami researchers rely on computers to try to figure out where waves might start and how they might behave. Some projects focus on predicting tsunamis. Others look at how such waves move and what happens when they hit land.

In a few places, such as Oregon State University in Corvallis, researchers even use wave machines that produce mini-tsunamis in the laboratory.

"We're pretty good at knowing where a tsunami is going to go and how long it would take to get there," says Robert Dalrymple. He's a coastal engineer at Johns Hopkins University in Baltimore.

"What I think is the hard part," he says, "is figuring out what happens when the wave gets to shore. How does it go around breakwaters? How does it break? How does it run up on land and around structures?"

Tsunami basics

Tsunami is a Japanese word meaning "harbor wave." Most tsunamis form after a massive underwater earthquake. The recent Indian Ocean tsunami, for instance, was triggered by a powerful quake at the bottom of the ocean near the west coast of an island in Indonesia called Sumatra.

The Indian Ocean quake happened at a place called a fault line, where one of Earth's giant plates slipped underneath another. This pushed the top plate up as much as 15 feet over 600 miles of its length. The result was a ripple of major waves in all directions.

The types of waves that you usually see at the beach are actually formed by an up-and-down motion of the water. Tsunamis, instead, push massive amounts of water in one direction. They can move as fast as 500 miles per hour.

As scary as the gargantuan waves sound, tsunamis are rare enough that you shouldn't let worry about them affect your life. "The probability of having an earthquake and a tsunami when you go to the beach is pretty slim," Dalrymple says. "I would still go to the beach."

Still, knowing where tsunamis might happen and what signs to look for can be useful. One area of concern is a fault line in Monterey Bay, California. Another is a volcano in the Canary Islands off the northwest coast of Africa. Should the volcano erupt, it could set off a tsunami that would flood New York.

High risks

By far the highest risk is in the Pacific Ocean, especially near Japan and Hawaii. That's where most tsunami monitoring happens.

This buoy is one of six that provide warnings of tsunamis in the Pacific Ocean. National Oceanic and Atmospheric Administration

Scientists are keeping a close eye on a Pacific fault called Cascadia. A major tsunami struck there in 1700. Elsewhere in the Pacific, tsunamis caused by a massive underwater landslide off Papua New Guinea killed 2,100 people in 1998.

Scattered throughout the Pacific region, six special detectors sit and wait for changes in water pressure, which would signal a tsunami. When the detectors sense a change, they send signals to a buoy on the surface, which then transmits signals to a satellite in space. Within minutes, the message arrives at centers in Hawaii and Alaska. Sirens follow to warn people to move inland.

There's no such system in the Indian Ocean. That's one big reason why the recent tsunami was so catastrophic. Very few people knew that a giant wave was on its way.

Even when monitoring is in place, you still need ways to warn large numbers of people very quickly about an impending disaster.

Public education

Public education programs could help prevent future deaths, Dalrymple says.

As a tsunami approaches, beaches can actually get wider as water recedes before the waves arrive. In places such as Thailand, people went exploring on the newly exposed sand, only to be struck by huge waves that can move as fast as 30 miles per hour when they hit land. You can't outrun a tsunami.

It's also important to know that tsunamis often arrive in several waves up to 90 minutes apart. The first wave isn't always the biggest. So, if one major wave hits, get to a safe spot and stay there for longer than you might otherwise think is necessary.

The location and construction of buildings can make a difference, too.

To predict what kind of damage a tsunami might cause depending on the lay of the land, Dalrymple uses mathematics to describe the motion of water. Then, he includes factors that change the way a wave breaks, such as the shape of the coastline, the width and steepness of beaches, the size of reefs, and canals and rivers that allow water to rush inland.

These satellite images show the shoreline of Banda Aceh in Indonesia before (top) and after (bottom) the Indian Ocean tsunami struck. One bridge is destroyed and much of the shoreline has disappeared. DigitalGlobe

"You start out by doing lots of idealized waves," Dalrymple says. "Then you look at possible shapes, waves on different slopes, waves running around walls of buildings. Then you create a catalog of all the different situations."

Dalrymple is interested in figuring out how to design buildings in tsunami zones to reduce damage. Although his research is still at an early stage, he already has some recommendations for tsunami defense.

Houses on stilts is one possibility. Another is to build protective walls that block out the sea. People in Japan sometimes do that already.

Aftermath

There are dangers even after a tsunami hits. One fear is that diseases such as cholera will spread if people can't get access to clean drinking water. Malaria and dengue fever are also concerns in the affected areas around the Indian Ocean.

"Water rushing in from the Indian Ocean can create pools of water where they didn't exist before," says Crispin Pierce. He's a professor of environmental public health at the University of Wisconsin, Eau Claire.

In some places, water flooded coastal areas as far as 1 kilometer inland, Pierce says.

Saltwater and polluted runoff can get into drinking water, making people sick. Disease-carrying mosquitoes also have more places to breed when there's a lot of water around.

So far, Pierce says, there hasn't been a big surge in disease. That's one positive note amid lots of sad news.

As long as people continue donating money for food, water, and medical care, and there are ways to get supplies to affected populations, the tragedy might not grow any worse. Pierce encourages kids to donate their allowances to relief organizations if they want to do something to help.

In the meantime, analysis and research continues. You can't stop the earth from cracking and groaning at unpredictable times. You can, however, prepare yourself to react in the best possible way, not only to giant waves but also to other natural disasters that might come your way.

Source: "Wave of Destruction." Science News for Kids. http://www.sciencenewsforkids.org/articles/20050119/Feature1.asp (accessed August 15, 2007).