San José, Costa Rica, since 1956

Poás Volcano Heats Up

SCIENTISTS are monitoring the lakein the active Poás Volcano’s main craterfor further temperature changes after itheated up last week and began to releasehydrochloric acid, sulfuric acid and sulfurdioxide.Emergency officials say they are preparedto mobilize if the situation worsens.If the volcano in Alajuela, northwest ofSan José, continues to heat up, the gases itis throwing into the air could produce acidrain, as it has in the past, according to astatement from the Volcanological andSeismological Observatory (OVSICORI)of the Universidad Nacional (UNA).At risk are the plants and animals ofthe national park around the volcano andpastures in the higher elevations, strawberryand dairy farms in the mid-range elevations,and crops such as coffee, bell peppersand tomatoes in the lower elevations.LAST week, the lake’s temperaturesurpassed 40° C (104° F), the temperatureat which hydrochloric acid evaporates.Changes in the lake’s temperature arecaused by a temperamental bed of hotmagma hundreds of meters below the surface.Cooked over that heat, gases rise tothe surface, their intensity dictated by thepaths available through the changingunderground network of vents.The gases dissolved in the lake arereleased in greater quantities as the lakeheats, a phenomenon that occurs periodicallyat Poás. The most recent times thelake heated significantly were in 1981,1987-90, 1994 and 1999.DURING one of the volcano’s moreactive periods in mid-1994, at least 20farmers lost most of their crops to acid rain(TT, June 24, 1994). Nearly 1,000hectares of pastures and crops such as coffeeand avocados were damaged and 173head of cattle suffered diarrhea and otherills effects.One month later, the volcano erupted,spewing a 700-meter high column of gasesand ejecting rocks into the air that landedback inside the crater (TT, July 29, 1994).The gases further exacerbated the acid rainproblem in communities as far as 10 kilometerswest and southwest of the volcano.The degree of destruction and the distanceover which it spreads depends on theamount of gases released, water vapor inthe air – which is higher now as the rainyseason begins – and wind speeds, OVSICORIsaid in the statement.THOUGH the lake has heated, it hasnot released a great amount of hydrochloricacid, scientists say.Regardless, emergency authorities areaware of the danger of possible severe airpollution and acid rain, and have alertedthe communities downwind of the volcano.Northwest Central Valley towns suchas Zarcero, San Juan de Naranjo andGrecia were damaged in past intense periodsof acidification.The National Emergency Commission(CNE) has kept threatened communitiesinformed through radio and press announcements,and says it will alert its actioncommittees if there is reason for concern.Scientists are downplaying the dangerfor now, however.“Most of the environmental acidificationis restricted to a very small area closeto the peak of the volcano within thenational park, as is normal during periodsof moderate activity,” OVSICORIresearchers said in the statement.

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