Volcanologists have come a long way since Mt. Vesuvius buried Pompeii. Now they have at least a fighting chance of predicting a volcanic eruption. Yet researchers who specialize in volcanoes still don’t fully understand the gaseous warning signs that spew out of active peaks. The composition of the smoke holds invaluable clues, but sampling the gases is dangerous and is often impossible as the eruption begins.

To provide a safer, continuous way of analyzing volcanic gases, physicists and geochemists at Los Alamos National Laboratory in New Mexico have used a remote sensing device to monitor plumes billowing from Popocatepetl, an active volcano 70 kilometers outside of Mexico City. The concentration of one of the gases depends on the temperature within the volcano, making the device “essentially a remote thermometer,” says Steven Love, a physicist at Los Alamos.

The remote thermometer is a version of a lab instrument commonly used to identify gases based on their characteristic absorption and emission of infrared radiation. By silhouetting the hot volcanic plume against the “cold” background of the sky, Love and his co-workers can measure the concentration of telltale gases formed by the volcano’s complex chemistry.

The next goal is to develop an automated, continuous warning system. Love explains that if the scientists can figure out the characteristic sequence of gases emitted prior to a major eruption, it “could give us real predictive powers.” Popocatepetl, like other active volcanoes, is closely monitored for seismic activity. Notes Love, “Working together with seismic monitoring, [the new technique] could certainly increase the probability of meaningful predictions.”

For those living under the shadows of active volcanoes, that could mean feeling just a bit less threatened by the nearby smoking giant.