The Poas Volcano crater as seen Tuesday morning. The most obvious change is that the lagoon grew some 40 meters in diameter, the ‘domo’ is gone and the water level dropped. Also evident are the giant rocks, that were not there before, on the ‘playon’ (the flat area) on the south side of the crater. Photo Gino Gonzalez

Q COSTA RICA – Last Friday, April 14, at 7:56am, the Poas Volcano left behind a period of relative calm, with small emanations of ash, mud and small stones, and went to a more explosive activity, which experts believe will include eruptions of up to five kilometres in height.

The change, volcanologists and geologists stay, occurred in a relatively short period of time that began at the end of 2015.

On Friday, the eruption sent a plume of gas and ash up to three kilometres high.

Following Friday morning’s activity, the eruptions at the colossus intensified. Although the emanation was mainly of gas, ash and steam, there were also ballistic elements (stones), expelled with great force landing in the visitor lookout and trails of the national park.

Specialists concur that from that moment the scenario changed.

The volcano is expected to become more violent, with a greater release of ash and stones at a considerable distance.

Tuesday night, at 7:08pm, was the latest eruption. The Ovsicori said the eruption was recorded only by seismic instrument, given that the gloomy weather conditions atop the colossus prevented observation by cameras.

Volcanologists Guillermo Alvarado Induni, Gerardo Soto Bonilla, Raúl Mora Amador and Mario Fernández Arce, explained that the rapid alternation of the behaviour of the colossus is due to some “unknown disturbance” in the reservoir of magma (believed to be one kilometer from the surface).

As the amount of magma grows and when it comes in contact with the hydrothermal system (water that is infiltrated by rain), it causes the warm to warm and evaporate. In addition, the magma and all the other elements seek to rise to the surface, explained the experts.

For the experts, this internal change also caused the volcanic structure to deform, allowing magma to continue to rise and cause the explosive eruptions, moving from phreatic eruptions (gas, water and ash) to the phreatomagmatic.

Major tourist destination
The Poas volcano is a major destination for tourists visiting Costa Rica and nationals alike. Visits to the national park by many are daily. The road leading to volcano has become a source of income for many, including entire families who work the restaurants and souvenir shops. One of the stops that cannot be missed are the shops selling strawberries from the Poas.

Activity at the Poas
The Poas had registered eruptive cycles in 1834, 1940 and between 1953 and 1955. Although there were episodes of activity in 1989, 1990, 1994 and 1999, on those occasions the emanations was acid rain.

During 1953-1955 the eruptions were uncountable and responsible for the creation of the ‘domo’ – the volcanic dome – from the lava. Last Sunday’s eruption completely destroyed the domo.

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