Impact craters created by the rocky material expelled by the active crater of the Turrialba volcano. (Pnhoto courtesy of Raul Mora)

The image of lava pouring out of the crater is one that comes to mind when we think of active volcano and eruptions. Although incandescent material has been observed in the mount of the volcano, the Turrialba has yet to spew lava.

That does not mean that the Turrialba is a tame volcano. Quite the contrary, the volcano within a slingshot of the Greater Metropolitan Area (GAM) of San Jose, is explosive and dangerous.

In fact, it is currently recording pyroplastic flows – hot clouds composed of gases, solid materials and trapped air from the crater moving rapidly down the slopes – which can reach temperatures of between 60 and 70 degrees Celius (140 and 158 degrees Fahrenheit).

The emanation can affect the respiratory tract, eyes and skin.

La Nacion from data provided by the Red Sismologica Nacional (RSN ICE UCR) shows the Turrialba volcanic hazards

The latest report of an eruption is 1:33am (local time) last Sunday, as the colossus began releasing a small continuous column of ashes that has become constant. At 7:52am (local time) Wednesday explosions from the Turrialba were heard after almost two months of relative calm.

For this reason, volcanologists emphasize the importance of respecting the restriction zone established by the Comision Nacional de Emergencias (CNE) – National Emergency Commission, that is from two to five kilometres from the active crater.

“When a powerful eruption occurs, a column of ash rises and often that column is no longer supported because the volcano stops feeding it. Generally, as it rises, its gases get to have the same density of the atmosphere and there it is, it’s a huge explosion,” volcanologist with the Preventec program at the University of Costa Rica, Raúl Mora, told La Nacion.

Image explains why Costa Rica’s volcanos are so explosive. Olga Cajina, La Nacion

“People need to be clear that this is a very dangerous volcano,” Mora said, adding: “The volcano does not stop, it is becoming more active and unstable.”

Respecting the rings of prevention

The northern sector of the Turrialba volcano, facing the Caribbean, is a national park and is covered with vegetation. However, on the southern and eastern sides, people live there.

As the last eruptive period of the Turrialba back to 1864 – 1866, “the perception of the residents is that it was a mountain and they kept getting deeper in the mountainside, planting and breeding livestock. People did not size it up as a volcano,” commented Mora.

But, despite declaring the surroundings of the active volcanoes as national parks in the middle of the twentieth century, which helped in terms of security, “in Turrialba, currently, there are animals were they should not be and are being affected by the ash. There are people living in these area and that is very dangerous,” said Javier Pacheco, volcanic seismologist at the Volcanological and Seismological Observatory of Costa Rica (Ovsicori).

After remaining quiet for over a century, the Turrialba woke up in 2007. From January 2010 has been constantly active, with serious eruptions recorded in October 2014 and March 2015.

Eruptions last year forced authorities to suspend San Jose air traffic on several occasions, the last in September.

Source La Nacion