Volcano watch

The US Geological Survey has good news for holiday air travelers. There's much less risk of flying into a dangerous volcanic dust cloud than there was a year ago.

Thomas Casadevall from the USGS Reston, Va. office explains that a much needed global volcano monitoring and warning network is coming into operation. The United States unit, located in Alaska, already gives coverage for North and Central America and some of South America. And its advisories are becoming a routine part of pilots' preflight briefings.

Dr. Casadevall told a meeting of the American Geophysical Union last week he expects the worldwide network to be fully functional by holiday travel time next year.

The volcano watchers use a combination of satellite surveillance and ground instruments located at active volcanoes. These help volcanologists forecast eruptions as well as spot eruptions in progress.

Volcanic dust clouds are hard to see. They may look like ordinary water clouds and may be invisible at night. Aircraft radar does not detect them and pilots can fly into them unwittingly. Casadevall said there have been 100 damaging dust cloud incidents over the past 25 years.