Costa Rica heats up.

AuthorHodgson, Susan Fox

At least twenty volcanoes are erupting in the world right now, and Costa Rica's youngest and most active volcano, Arenal, could be among them. Arenal's eruptions date back 7,000 years but the current surge of continual activity began in 1968. The exact number of volcanoes in Costa Rica is unclear. In a country of 19,730 square miles (a little smaller than the state of West Virginia) one Costa Rican map includes fifteen volcanoes, but more show up elsewhere. The fact that newer volcanoes tend to form within parts of older ones, and that single systems of magma--underground lava--form multiple volcanic features add to the confusion about the exact number. In any case, Costa Rica has seven historically active volcanoes, and Arenal is listed as twelfth under "some of the world's most active volcanoes" on the Volcano Watch website prepared by Michigan Technological University.

Costa Rica's geological singularity is caused by its location along the Pacific "ring of fire." You may recall the earth's surface is made of many plates pushing alongside, away from, against, and under each other. On Costa Rica's Pacific shore, the oceanic plates--those beneath the ocean--curve and descend beneath the continental plate on which the country rests. When the oceanic plates are over 62 miles deep, they melt and the melted rock, called magma , resurfaces and erupts into the Costa Rican countryside, forming the land we know.

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You can imagine how violently vast amounts of moving magma must shake and break nearby rocks (we feel the earthquakes) and how hot these rocks can become. Rain and surface waters flow down into these hot rocks, often through the breaks--called fractures and faults . The water can heat to very high temperatures and, if it becomes trapped underground, voilà , we have what we need: a geothermal reservoir. Geo means earth and thermal means heat; geothermal resources are heat from the earth that we can use to generate electricity.

To do so, we must first find underground hot-water reservoirs, drill wells into them, extract the hot water, and allow steam from the water (formed by lowering the pressure) to turn a turbine. This is what produces electricity.

According to the International Geothermal Association, Costa Rica is the seventh most productive country of the 25 that produce geothermal electricity in the world today. About 13 percent of its electricity comes from geothermal resources.

Here is Costa Rica's geothermal...

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