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Chouet is not the only researcher who's using the orbital high ground to study the volcanic underground. In Alaska, USGS researchers have placed satellite receivers at different points on the sloping side of the Augustine volcano and tuned them also to the gps. Like any volcanic mountain, Augustine is swelling slightly as it fills with magma. The degree of this deformation--as calculated by the gps--can help determine the imminence of the eruption. Elsewhere, scientists are leasing time on European or Japanese satellites to take photos of volcanic peaks as they undergo a seismic event like an earthquake. Imaging hardware then measures the precise distance between the satellites and any point on the mountain. If that distance changes as the spacecraft make repeated passes over a peak, scientists can determine how much the ground moved as a result of the event and, by inference, how stable it is.
But cracking volcanic secrets doesn't always require such sophisticated instruments. Increasingly, researchers have come to appreciate that volcanoes, like living organisms, have their own internal metabolisms, and like any metabolic system, they give off telltale waste products--particularly gases. Williams is developing a new way to read those gases and predict just when a mountain will probably detonate.
As magma rises in a volcano, light molecules like carbon dioxide bleed off more than heavier gases like sulfur dioxide. The higher the CO levels, the likelier an eruption. If magma gets stuck in the gullet of the mountain, SO predominates. The more SO, the more stagnant the magma and the less probable an eruption. The problem is that taking accurate measurements may require climbing almost directly into a volcano--a decidedly dangerous proposition.
To reduce the risk, Williams is testing a remote gas sensor that can read a volcano's emissions from a plane flying nearby or even a car driving past at a distance of as much as 20 miles. The instrument works by detecting changes in the infrared energy caused by different gases in the volcanic plume. Says Williams: "Volcanoes give gaseous signals of approaching eruptions. This gives us the lead time we need to get people educated and not terrorized."
Even if new gas-sniffing and satellite equipment succeeds in keeping people on the ground safe from volcanoes, people in the skies could still be at risk. For them the danger comes from volcanic ash, which can choke the engines of passenger jets. Since the 1960s there have been 85 such midair encounters, and while none have led to a fatal crash, some have come close.
To combat the problem, the USGS is deploying detectors around volcanoes so that air-traffic controllers can be alerted when an ash cloud belches forth. While this could go a long way toward making the skies safer, the business of setting up the instruments is going slowly. Currently, the faa, which funds the project, is devoting only $2 million a year to it, barely enough to equip two volcanoes. At that rate, it would take 275 years before all the world's active peaks were covered.