MercoPress. South Atlantic News Agency

“Pompeii scenario” forecasted for Chile's Chaitén volcano

Chilean authorities are considering the possibility that Chaitén volcano in continuous eruption for over a week might collapse and release a torrent of red-hot pyroclastic material (burning gas and rocks) that could devastate the surrounding area.

Very much a "worst case scenario," the possibility is nevertheless a very real one, vulcanologist Luis Lara of Chile's National Geologic and Mining Service (SERNAGEOMIN) told reporters Thursday afternoon. "That's precisely the reason we recommended that authorities define a restricted area, because this is a real possibility with volcanoes that are similar to Chaitén. We can't offer any kind of probability that this will happen, or say for sure how things will play out. It's a worst case scenario" said Lara. There is precedent for such concern, according to the SERNAGEOMIN official who pointed out that similar volcanoes (in Mexico and the Philippines, for example) have collapsed on the seventh or eight day of continuous eruption. "Pompeii is in some ways similar," added Lara, referring to the Roman city famously destroyed in AD 79 by Mount Vesuvius. "There was a pyroclastic flow that resulted in the consequences we all know. That's exactly the worst case scenario that we've defined here". Pyroclastic flows are rapid currents of hot gas and rock that can escape from a volcano crater and travel downhill toward surrounding areas. Lara and his colleagues, in fact, have already observed such pyroclastic escapes in photographs and video recordings of the ongoing Chaitén eruption. "There's evidence that this is happening. One can see pyroclastic flows descending past the edge of the dome, where the craters are located. Although they aren't very dense and are of relatively small volume, they're crashing against the walls of the cauldron and have burned vegetation," said Lara. The vulcanologist suspects such flows are responsible for a noted temperature increase – of between 7 and 17 degrees Celsius – in the nearby Chaitén and Raya Rivers. The eruption, the Chaitén volcano first in recorded history, released a massive billow of ash that was visible as far away as Puerto Montt, some 200 kilometres to the north. Volcanic soot began to rain down, blanketing the town of Chaitén and other area towns like Futaleufú, and contaminating local water supplies. The volcanic activity intensified late in the week as authorities reported seeing lava emanating from the volcano's crater. The natural disaster prompted government officials to order the mandatory evacuation of local residents and all emergency workers within 50 kilometres of the volcano. So far the volcano, located some 1.200 kilometres south of Santiago, has emitted some two cubic kilometres of ash, said Lara. Smoke from the crater has shot up as high as 15 kilometres. The massive plume of smoke, furthermore, now stretches as far away as Buenos Aires, Argentina, some 500 kilometres to the east. The Santiago Times