Although tremendous strides have recently been made in monitoring the world's active volcanoes, it is always the unsuspected eruptions from volcanoes considered to be inactive and with no historic track record of eruptions that will take the scientific and local communities by surprise and cause the greatest destruction to life and property. A sobering fact is that 12 of the 16 largest and most devastating eruptions of the past two centuries have come from such volcanoes ( Simkin, 1993). The only way to identify the volcanoes most likely to erupt soon is to continue to undertake routine physical and geochronological studies on as many volcanoes as possible, but often the choice of which volcanoes to study is based on criteria of scientific inquiry rather than hazard potential. The Decade Volcano may help raise the general level of awareness to this problem, Mount Rainier, which has had no historic activity, being a case in point. Little is known about the past behavior of this large volcano that dominates the Seattle-Puget Sound area, but future projects will redress this imbalance ( Wright and Pierson, 1992).
No hazard assessment and prediction will save lives and property without the full cooperation of the local civil (and perhaps in some nations, military) authorities of the threatened areas, a lesson tragically learned at Armero, under Nevado del Ruiz, Colombia, in 1985 ( Voight, 1990). It is comforting but perhaps inadvisable to assume that the situation regarding communications between volcanologists and the general populace and their officials has improved, despite the resounding success of the actions taken at Pinatubo (Pinatubo Volcano Observatory Team, 1991) and Rabaul.
Aircraft-ash encounters are another area for concern. There have been several near-fatal accidents, the most spectacular being the 747 Jumbo jet crippled by ash from Redoubt while entering Anchorage air space on 15 December 1989 ( Brantley, 1990). Hopefully the Federal Aviation Agency's (FAA) volcanic ash avoidance procedure will avert any future disasters from ash being ingested into jet or turbo-jet engines ( Casadevall, 1994). Nevertheless, there is a critical need for increased surveillance of volcanoes in the context of aircraft safety, particularly over remote volcanoes along established commercial air routes (e.g., the North Pacific).
At the time of writing, the September-October 1994 eruption of Rabaul, New Guinea had not occurred and several significant publications concerning recent eruptions and new advances in volcanology were in press. These include special issues on the Redoubt, Pinatubo, and Spurr eruptions, and a commemorative journal issue of those killed at Unzen. The next four years will prove highly challenging for the volcanological community, especially if the volcanoes keep up their recent pace and magnitude of activity.
Acknowledgments. We thank the NASA Earth Observing System program for support and two anonymous reviewers for comments on this manuscript. This is SOEST contribution 3818.