The magnificent Turrialba in April 2012. Source: RSN

Geologists from the National Seismology Network (RSN in Spanish) of the University of Costa Rica (UCR) are keeping a close eye on the seismometers located around the Turrialba volcano in the Cartago province, coordinates 10°2′0″N 83°46′0″W. Costa Rica is located in a region known for high seismic and volcanic activity, and to this extent geologists and emergency management officials are constantly vigilant.

The RSN recently published a report that indicates an unusually high amount of seismic activity took place around the Turrialba and Irazu colossi during the month of May: 22 earthquakes with a magnitude greater than 2 on the Richter scale. A dozen other earthquakes were also detected in the area during June, but RSN researchers are mostly concerned with micro quakes (less than 2 on the Richter scale) occurring near the Ariete and Elia geological faults located parallel to each other on either side of the Turrialba volcano.

In an article by Carlos Arguedas of national newspaper La Nacion, renowned geologist Wilfredo Rojas explained that the Ariete fault routinely produces an average of five micro quakes per week, but the main concern is focused on the possible impact those earthquakes could have on the magma of the Turrialba. Readers of The Costa Rica Star may recognize Mr. Rojas as the geologist who in 2008 found the Porvenir stratovolcano on foot and without advanced instrumentation, a unique finding in the 21st century. Mr. Rojas is also leading the search for the missing TC-48, a military aircraft from the Argentinian Air Force that disappeared in 1965 while flying over Costa Rica, one of the most intriguing unsolved mysteries in the history of aviation.

The concern over the relation between the volcanic matter of the Turrialba and its proximity to the geological fractures is twofold: earthquakes can disturb the magma and cause a dangerous eruption, or the magma can exert enough pressure on the fault to trigger a significant earthquake. There is no indication at this time, however, that the magma has moved significantly.

RSN geologist Mario Fernandez pointed out that seismic activity produced by the Ariete fault could be behind the sudden opening of fractures on the volcano surface that are releasing noxious gases. The Turrialba National Park and the surrounding communities have been kept on green alert for this reason, and also because of the recent spectacular -yet largely phreatic- eruptions. The Turrialba is not the only volcano in Costa Rica under alert: the Poas and Rincon de la Vieja volcanoes are under green alert as well, and constant monitoring is in place by means of eyewitness reports and drone flights.

The Turrialba eruptions have triggered acid rain, which has affected the local agricultural and livestock economy. The pH (potential Hydrogen) count of rainfall samples collected in April was as low as 3.21. The pH scale for water runs from 0 to 14, with drinking water rated at 7 -indicating neutral acidity. When pH levels fall deeply below 7, water becomes harmful for many organisms -including humans.

The report from the RSN also indicated that 2012 has thus far been a shaky year for Costa Rica. The country currently averages six earthquakes per day, and some seismic clusters have delivered a handful of quakes over a single weekend. Fortunately, no major damage or injury has been reported.