A giant, 40 stories tall wave could one day drench the eastern United States, the result of an asteroid-driven tsunami. However seaside dwellers need not move just yet, the asteroid isn't due for another eight centuries.
Researchers in California have developed a computer simulation depicting the ocean impact of the asteroid 1950 DA, a half-mile wide (1.1-kilometer) space rock that swings uncomfortably close to Earth in 2880. Although the probability of such an impact is remote to say the least -- astronomers estimate it to be somewhere around 0.3 percent -- the computer model does give researchers insight into the destructive power of tsunamis caused by near-earth objects.
"You'd want to first decide how far away [from impact] the effects are going to be felt," Steven Ward, a research geophysicist at the University of California Santa Cruz (UCSC), said in a telephone interview. "And once you know that, maybe you could set up a zone of evacuation." According to Ward's research, about 120 million people live in coastal areas at elevations within 65 feet (20 meters) of sea level and just over a mile (two kilometers) of the ocean.
Ward is the lead author of the simulation study, which will appear in the June issue of the Geophysical Journal International.
Ward and co-author Erik Asphaug, an associate professor of earth sciences at UCSC, used 1950 DA as the asteroid in their simulation because of its history. Astronomers first discovered the asteroid in 1950 and tracked it for 17 days. The object was seen again in 2000, when researchers determined its radius and other characteristics. Its most recent Earth flyby last year led researchers to determine its future paths up through 2880, when it crosses the planet's orbit.
Asteroids are fascinating objects because they're the only disasters that you can prepare for, not like volcano eruptions, earthquakes or major storms," Asphaug told SPACE.com.
On March 16, 2880 the Earth's Atlantic Ocean is turned toward 1950 DA, and with 70-percent of the Earth covered in water an ocean impact would be the most likely to model.
In the simulation, 1950 DA slams into the Atlantic Ocean about 360 miles (579 kilometer) off the eastern coast of the United States. The asteroid, traveling at 38,000 miles an hour (61,155 kilometers per hour), is vaporized in the impact's 60,000-megaton blast and blows a hole in the ocean straight to the seafloor.
Seawater rushes into the cavity, which spans 11 miles in diameter and three miles deep (about 17 kilometers wide and five deep), and a halo of waves begin their journey outward from the impact site like overgrown ripples from a pond. Two hours after impact, waves 400 feet (121 meters) high hit the coastline from Cape Cod in Massachusetts to Cape Hatteras in North Carolina, and could ultimately penetrate more than two miles (about four kilometers) inland.
1950 DA is one of the larger asteroids that astronomers worry might hit the Earth. On the average, space rocks its size strike the earth every 100,000 years or so. Smaller asteroids up to 300 meters wide do so more frequently, about every 5,000 years, and so pose a larger tsunami danger for coastal residents, Ward said.
Asphaug, who led a NASA-sponsored workshop on asteroid hazards in September 2002, said that while not a lot can be done about larger, kilometer-sized objects that can cause global devastation, some action could be taken for smaller rocks. Observations, for example, could be fed into the already existing Pacific Tsunami Warning Center to track potential impacts.
"It takes time for these tsunamis to reach coastlines from the point of impact," Asphaug said, adding that once a satellite spots the flash of an impact, there will be a period of hours before the first big waves hit the shore. "It's possible to think that in 800 years, we might have enough technology to pinpoint which areas to evacuate and then do it."
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