Volcanoes

Several national parks have been created around active volcanoes, with accommodations and viewing facilities, as well as lectures and guided walks to assist visitors in understanding the processes at work. A descriptive map charting the volcanoes is published by the Vulcanological and Seismological Observatory of Costa Rica at the National University in Heredia, which monitors volcanic activity throughout the nation.  (Libreria Lehmann and Libreria Trejos, in San José, may sell the map).

In 1963, Irazú (elev. 3,412 meters) broke a 20-year silence to begin disgorging great clouds of smoke and ash. The eruptions triggered a bizarre storm which showered San José in five inches of muddy ash and snuffed out the 1964 coffee crop, enriching the Meseta Central for years to come. The binge lasted for two years, then abruptly ceased. Poás (elev. 2,692 meters) has been particularly virulent during the past 30 years. In the 1950s, the restless four-mile-wide giant awoke with a roar after a 60-year snooze, and it has been huffing and puffing ever since. Eruptions then kicked up a new cone several hundred feet high. Two of Poás's craters now slumber under blankets of vegetation (one even cradles a lake), but the third crater belches and bubbles persistently. In 1989, a spate of intense eruptions and gas emissions forced Poás Volcano National Park to close (local residents were even evacuated), and the volcano is constantly monitored for impending eruptions.

A more spectacular light-and-sound show is given by Arenal (elev. 1,624 meters). Following a four-century-long Rip van Winkle-like dormancy, this 4,000-year-young juvenile began spouting in 1968, when it laid a four-square-mile area to waste. Arenal's activity, sometimes minor and sometimes not, continues unabated. Though currently more placid, Miravalles, Turrialba, and Rincón de la Vieja, among Costa Rica's coterie of coquettish volcanoes, also occasionally fling fiery fountains of lava and breccia into the air.

The type of magma that fuels most Central American volcanoes is thick, viscous, and so filled with gases that the erupting magma often blasts violently into the air. If it erupts in great quantity, it may leave a void within the volcano's interior, into which the top of the mountain crumbles to form a caldera (from the Portuguese word for caldron). Irazú is a classic example. Irazú's top fell in eons ago. Since then, however, small eruptions have built up three new volcanic cones--"like a set of nesting cups," says one writer--within the ancient caldera.

There are nine major volcanoes in Costa Rica, three of which are active. There are more than one hundred craters overall in the country, however. The most impressive include the active Arenal Volcano, with a near-perfect cone shape, the Poás boasts the largest crater and the Irazú, which is the tallest. On a clear day you can see both the Atlantic and Pacific oceans from the Irazú.

There are tours available to several volcanoes. The Arenal tour even stops at a hot springs resort. The explosions of the volcano can be heard often. The Rincón de la Vieja passes by fumaroles and boiling claypits. There are hikes, horserides and mountain bike tours available.