The Precious Acid Gas Bubbles

It is Day 8 of our expedition and we have ³rounded the bend² as we approach the northernmost destinations of our itinerary. We spent the day travelling overland from Volcan Arenal to the foot of Volcán Miravalles, located in the north-central plateau of Costa Rica. We are now near both the Pacific coast and the Nicaraguan border. The dry and windy environment here is in stark contrast to the damp, humid rain forest we have left behind.

Volcán Miravalles is a dormant stratovolcano on the edge of a very large caldera. In the near distance is the active Rincon de la Vieja, our next and final destination. Although dormant, Miravalles provides an exceptional opportunity for our scientific party to sample hot spring waters and the gases they contain (Hydrogen Sulfide and Carbon Dioxide).

Located on the southern flank of Miravalles is Costa Rica¹s only geothermal power generating plant. It is operated by the Instituto Costarricense de Electricidad (ICE) [pron: ee-say], and has been responsible for as much as 20% of the nation¹s power output. The following is a special report on ICE¹s mission and the Arenal-Miravalles Volcano Observatory by Guillermo Alvarado:

ICE and the Vigilance of Volcanoes

As you well know, Costa Rica has many active and dormant volcanoes localized in a highly tectonic region (many faults and earthquakes) and in a very tropical region with a lot of rainfall. It is precisely this reason that gives Costa Rica its potential for the exploitation of hydroelectric and geothermal energy. However, many of the sites of interest for these uses are located in areas close to volcanoes and to active faults. Because the geological activity of the region, investigations concerning geology, tectonics, seismology, and volcanology are critical to evaluating the feasibility and possible hazards to the structures and people involved. The ICE (Instituto Costarricense de Electricidad, Costa Rican Electrical Institute) is involved not only in prospecting and exploitation but also in hazard assessment and monitoring of these regions.

Observatorio Sismologico de Arenal y Miravalles (OSIVAM): The Seismological and Volcanological Observatory of Arenal and Miravalles

This observatory is located in the Northern zone of the country. Its primary purpose is to monitor the volcanoes near the geothermal and hydroelectric projects. These projects include the Geothermal Plant of Miravalles and the Hydroelectric Plant of Arenal, Corobici and Sandillal as well as the Geothermal Projects Tenorio and Borinquen-Las Pailas, the last of which is located at the foot of the Rincon de la Vieja Volcano. OSIVAM has digital seismological stations, strong motion equipment, and is involved in high precision geodesic studies, joined with the topographic team from ICE.

Miravalles Volcano and the Miravalles Geothermal Plant

Miravalles (2028M) is a volcano that has been dormant for thousands of years. However, it has had an explosive eruptive history, with activity for more than a million years. Since 1975, at the foot of Miravalles, the first studies for the development of the Geothermal Project took place. The results were actualized starting in 1994 and the energy from the Earth was tapped. The plant can produce 140MW of power and in 1998 provided 8% of the energy of the country. Today there are more than 43 drill sites with production ranging between 3 and 16 Megawatts. For example, 1 Megawatt produces enough electricity for 4800 people. This form of energy is highly advantageous as it is not dependent upon the rainy season or fossil fuels.