The current Turrialba eruptions are similar to 1864

Q COSTA RICA – The materials being spewed out by the Turrialba volcano are chemically similar to those of the previous eruptive cycle, dating back to 1864.

In 1863, Danish naturalist Anders Sandow Oersted reported cracks where smoke and vapor emanated from the colossus, while traveler Karl Hoffman described a column of smoke rising high and visible from the Irazu volcano.

And Alexander von Frantzius, also a naturalist, said he saw “flames shooting out of the volcano” and his colleague, Henri Pittier, reported that the ash ejected by the Turrialba reached San Jose, Greece and Atenas.

Does it sound familiar?

As the volcano today behaves in a similar way it did a hundred fifty years ago, during the 1864-1866 eruptive period, volcanologists see two possible scenarios: two more years of ash and gas or an eruption that could reach 7,000 metres (4 miles high) high.

Experts at the Observatorio Vulcanológico y Sismológico de Costa Rica (Ovsicori-UNA) say that of the little that they know of the 1864 activity and given that small amounts of magma what is expected is volcanic eruption. “What we have seen so far are small, strombolian eruptions that do not reach 6,000 metres in height,” said volcanic seismologist, Javier Pacheco.

In agreement with Pacheco, is Raúl Mora, a volcanologist working on the Preventc program at the University of Costa Rica (UCR).

“After the eruption, it is likely the Turrialba will return to rest. I hope so,” Mora said.

Both experts say the other possibility is that the volcano keeps doing for the next two or three years what it has been doing, and then become dormant without a major eruption.

“It’s a nuisance for everyone (because of the amount of ash), but it’s not a catastrophe,” said Geoffroy Avard, who is a researcher and analyzes volcanic materials (ash and rocks) at the Ovsicori Petrology Laboratory. “From the information provided by the materials expelled by the volcano, it seems that the Turrialba prefers to remain quiet”.

Avard is working with two hypotheses: it may be the same material that failed to emerge 150 years ago, or new magma is have the same evolution as in 1864-1866.

The ashfall in 1864-1866 affected some 40 cantons of Cartago, San Jose, Heredia, Alajuela, Limon and Puntarenas.

According to the experts, the Turrialba has the capacity to generate sub-Plinian eruptions that could rise as high as 20 kilometres.

“It has been a very active and dangerous volcano, its magma generates a lot of gas and that produces its explosiveness,” said Pacheco.

Source: La Nacion


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