ABSTRACT
The 1980s were the worst decade for volcanic disasters since the beginning of the 20th century. Over 24000 people were killed as a result of two eruptions: El Chichon in Mexico (1982) and Nevado del Ruiz in Colombia (1985). Other eruptions in the United States, Italy and Indonesia claimed some 100 lives, and a further 1800 died after carbon dioxide bursts from volcanic crater lakes in Cameroun in 1984 and 1986 (Tilling, 1989). At the time of writing, ongoing eruptions at Unzen in Japan, and Pinatubo in the Philippines, had resulted in many deaths and necessitated large-scale evacuations. It is selfevident that the local, regional, and even global impacts of eruptions demand that potentially active volcanoes be monitored regularly, and that volcanolegists should endeavour to interpret volcano behaviour so that meaningful predictions can be made. 530 volcanoes have erupted in historic times, and a further 2600 have been active in the last 10000 years (C. Newhall, personal communication). Unfortunately, only a tiny fraction of these potentially hazardous volcanoes is presently subjected to routine surveillance. Indeed, it is only since the advent of remote sensing that volcanologists have attempted merely to identify and catalogue all the world's active volcanoes (e.g. de Silva and Francis, 1991).
