Q COSTA RICA – Pressure from what experts call a “lava bag” – presumed on the rise – brought about sudden changed in the behavior of the Poas Volcano in recent weeks.
The escalation began on April 1, when several tourists recorded a phreatic eruption (composed of gas, steam and particles.
On Sunday (April 9) morning, seismic activity and gas emanation from at the colossus increased, forcing a temporary closure of the national park.
Although the Poas remained within the ranges already known by the experts, shortly before 2:00pm, an evacuation warning was issued to tourists due to the strong emanation of gases.
In the past two weeks, experts from the Observatorio Vulcanológico y Sismológico de Costa Rica (Ovsicori) report gas emanations went from an average of 19 tons per day to 180, the majority from the lagoon at the bottom of the crater.
Simultaneously, in less than eight days, the lake temperature rose from 35° Celsius to 40° Celsius (95 F to 104 F) to and the color that had remained milky green became milky gray.
Finally, a “small earthquake” that occurred at 7:23pm on April 6 saw the opening of a new fumarole, located 200 meters south of the dome.
A day later, the fumarole surprised park rangers and visitors, spewing out water up to 10 meters high, forming a river that ran down to the lagoon. The water temperature was recorded a 90° Celsius (194 Fahrenheit).
This and other events in the past several weeks lead Ovsicori experts to believe magma lies between 500 meters and one kilometer deep, pressing towards the cusp to spew out.
Maria Martinez Cruz of the Ovsicori said: “What has been happening since the beginning of January is that there is a volume of fresh magma, pushing from the depths to more superficial levels. That magma comes from a magmatic chamber that we do not know its size (…) the surroundings of that magmatic chamber are solid but brittle and if the magma pushes, causing fractures, then the magma can rise through the fractures in the forms of fingers of Magma “(like a hand).
Asked about the possibility of the magma reaching the surface, she answered that it is a possible scenario.
“Between 1953 and 1955 the Poas had magmatic phreatic eruptions, that is where the magma interacted with the hydrothermal system from which fragments of lava emerged (…), including lava flows, that lava surfaced and formed which we know as the dome,” she explained.
Volcanologists Gino González Ilama, of the Volcanes sin Frontera (Volcanos Without Borders) organization, made an inspection Monday, and among other findings said that inside the dome other sources of water could be observed.
He also said that in the lake are spheres of black sulfur, which suggests that these are particles subjected to very high temperature, which were burned.
The director of Poás Volcano National Park, Redy Conejo, confirmed that the park is open to the public, but in the event there is an increase in the emanation of gases and that they reach the lookout point, it could be decided to evacuate the visitors.
The gases cause respiratory problems and could affect mainly people with asthma.
