Mind the gap: inadequate monitoring at many U.S. volcanoes.

A report just released by the U.S. Geological Survey (USGS) ranks the threats posed by the nation's volcanoes, identifies gaps in monitoring at and around those peaks, and proposes a comprehensive early-warning system for volcanic unrest and eruptions.

The United States and its territories are home to 169 volcanoes that are now erupting, have erupted recently, or became dormant so recently that they may merely be napping. Since 1980, when Mount St. Helens blew its top, a total of 45 eruptions have occurred at 23 of those peaks. Currently, three U.S. volcanoes are erupting: Mount St. Helens, which reawakened in 2004; Hawaii's Kilauea, which has been continuously active since early in 1983; and Anatahan, a volcanic island about 320 kilometers north of Guam that rumbled to life from dormancy in May 2003.

Volcanoes pose a variety of threats, says Thomas L. Murray of the USGS in Anchorage, Alaska. Those hazards include torrents of lava, avalanches of debris and mud, and hot clouds of ash that sweep down the flanks of a volcano at highway speed (SN: 1/13/01, p. 21). People on the ground aren't the only ones at risk. Several commercial jets have narrowly escaped high-altitude encounters with plumes of volcanic ash (SN: 9/13/03, p. 168).

Murray and his colleagues have tallied the threats posed by each of the nation's volcanoes. The team considered factors such as the frequency and strength of past eruptions, the number of people living nearby, and whether aircraft fly over or land in that area. Although the analysis concluded that 18 volcanoes pose a very high threat to people and aviation, only three of those peaks are now rigged with sufficient monitoring equipment. Scientists completed fitting two of those three with their current complement of instruments only after the volcanoes began erupting.

Altogether, only a dozen or so U.S. volcanoes are monitored as well as they should be, says Murray. Priorities cited in the new USGS report include adding instruments at 13 poorly monitored, high-threat volcanoes and placing new equipment at 19 volcanoes that currently have no instruments nearby.

If instruments are in place on hazardous volcanoes before they rumble to life, scientists and emergency-management personnel don't have to play catch-up when the seismic activity under the peak increases or eruptions occur, says Murray. Because a volcano's pre-eruption signals can be subtle, it's especially important to improve the instrumentation around threatening peaks, he notes.

The new report, released last week, also calls for a national volcanic-watch office that would be staffed around the clock as well as a computer network that would enable scientists at several locations to immediately analyze massive streams of data from a volcano.

Murray and his colleagues have "done a good job of assessing the current needs and capabilities" of scientists tasked with monitoring the nation's volcanoes, says David A. Schmidt, a geophysicist at the University of Oregon in Eugene. The proposed effort, he adds, could put geologists in a much better position to forecast volcanic activity than they were when Mount St. Helens erupted a quarter of a century ago.