A series of earthquakes around the Washington state mountain and a gush of steam and ash into the air Friday indicated that red-hot magma may be welling up from below.
The volcano is not expected to have an explosion as dramatic as its fatal and devastating eruption more than two decades ago, when part of the mountaintop collapsed, hundreds of square miles of nearby forest were leveled, and a cloud of ash turned day into night.
But that doesn't mean that scientists, area residents and tourists aren't keeping a close eye on things. A "VolcanoCam," for instance, monitors Mount St. Helens from the Johnston Ridge Observatory, about five miles away.
As the volcano slept in recent years, scientists and engineers have labored to come up with better devices and methods for capturing its vital signs. Most significant is global positioning system technology, which pinpoints locations on earth with the help of satellites in orbit. GPS has allowed geologists to chart how the ground shifts around a volcano without the use of laser-ranging devices, which measure distance using lasers and reflector targets placed on a volcano.
A continuing challenge, however, is that no one can ever be sure where the next big blow-out will come. Hence, researchers had given greater attention to sites other than the Washington state volcano.
"Nature isn't necessarily going to have its next major activity where you have the most instruments," said Chris Newhall, a research scientist with the United States Geological Survey and a professor at the University of Washington.
Digital seismometers far more sensitive than their precursors are among the advances for monitoring earth movements and potential volcanic activity. But older analog seismometers that date back 24 years are still in use in the Mount St. Helens region. The newer machines are listening to vibrations in the Long Valley region of California, which generally has much more equipment for sniffing out geologic rumblings, Newhall said.
GPS units, meanwhile, provide readings that are both precise and frequent, said Ken Hudnut, a USGS geophysicist based in Pasadena, Calif. The devices, which can be as small as the size of a cigarette pack, are placed around volcanos and can be powered by solar panels or batteries.
"Every second, we can know the position of that GPS unit to about a centimeter," he said.
This is more accurate than many consumer GPS devices, in part because of high-end antennas, Hudnut said. In total, a precision GPS unit can retail for about $20,000, he said.
Friday's blast claims tech gear
At Mount St. Helens, there are about a dozen sites where researchers take GPS units for measurements. But there are only about four to six units currently on the volcano and sending out data, Newhall estimated. A piece of GPS gear was put in the volcano's crater Monday, but it was lost in the blast Friday, which also took out a seismometer.
It would be nice to have more GPS units on the mountain to better see how it is shifting, Newhall said. "One of the difficulties we're having right now is we didn't have a whole lot of them out there."
Another advance for tracking the changing shape of a volcanic area is a type of satellite radar called interferometric synthetic aperture radar. This system works by having satellites zap radar signals to the Earth's surface and examining the way they bounce back. It's a good method for getting an early warning on seemingly dormant areas, Hudnut said.
"This has been very helpful for picking out the volcanos that are starting to be active but have not yet become very obvious or noticeable," he said.
Old-fashioned aerial photography also has improved considerably, thanks to the advent of digital cameras. Digital cameras combined with GPS readings and gyroscopes can translate into topographical maps much more quickly than in the past, Hudnut said.
"What used to take weeks, now takes hours," he said.
Across the world in Italy, a Web cam is trained on Mount Etna, which began to discharge lava last month. The camera connects wirelessly to a notebook computer equipped with Intel's Centrino wireless technology, with the computer housed in a protected container. At the top of Mount Etna's crater, a wireless hot spot has been set up, which transmits images from the notebook computer to a Web server in Sicily.
Robots have a checkered history in the field of volcanos. A few years ago, NASA built a spiderlike robot designed to go into craters, Newhall said. Conceivably such a machine could bring additional sensors into a volcano. The robot was similar to one that appeared in the movie "Dante's Peak," where it didn't succeed in its mission.
"The NASA one worked about as well as the one in the movie," Newhall said.