Long-term fluctuations in volcanic activity: implications for future environmental impact

Acidic crater lakes at persistently active volcanoes act as both an index and a moderator of volcanic processes. A catastrophic drop in lake level can therefore lead to serious local environmental damage. In the early 1990s, the crater lake at Poas volcano, Costa Rica diminished, and acid aerosols erupted with devastating consequences for local health, environment and economy. The first indications of this event can be retrospectively identified to have started from 1985, on the basis of our unique 20-year data time series, which provides evidence for the shallow intrusion of magma. New data presented in this article show similar trends and we conclude that Poas has now entered another active period with renewed intrusion. Severe environmental damage in this region is expected within the next few years if the current trend continues.