20 June 2012

A year later, the effects of a volcanic eruption still plague Patagonia

On June 3 2011, Patagonia cracked open. A thick brown cloud of ash shot nine miles into the air, ejected from the Puyehue-Cordón Caulle volcanic complex in Chile’s lake district. Within hours, ash was raining down on both sides of the Argentine-Chilean border, forcing schools, roads and airports to shut down. Now, more than nine […]

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On June 3 2011, Patagonia cracked open. A thick brown cloud of ash shot nine miles into the air, ejected from the Puyehue-Cordón Caulle volcanic complex in Chile’s lake district. Within hours, ash was raining down on both sides of the Argentine-Chilean border, forcing schools, roads and airports to shut down. Now, more than nine months later, the complex is still rumbling and sending ash billowing into the Argentine resort towns of Bariloche and Villa La Angostura.

Puyehue-Cordón Caulle sits along an eighteen-kilometer section of the Andes about 100 kilometers east of Osorno in southern Chile that churns with volcanic activity. It has more than 60 historically or potentially-active volcanoes. Last June’s erupton didn’t originate in a single crater but came from many fractures and fissures. One hundred million cubic meters of pyroclastic material were released per day in the initial phase of the eruption, according to Chile’s National Geology and Mining Service (Sernageomin). 3,500 people were evacuated from the immediate vicinity in Chile and towns as far as Bariloche in Argentina—about 130 kilometers away—were blanketed in a foot of volcanic ash that short-circuited power lines and closed highways.

“We’re going to be paying for this for years,” says Gustavo Villarosa, a volcanologist based in Bariloche at the National University of Comahue. The ash fouled the city’s sewage treatment plant and municipal water purification system, says Villarosa. “The pumps corroded, the filters were blocked up” Local officials had time to plan for the eruption but didn’t, he says.

In the weeks leading up to the eruption, Villarosa and his colleagues met several times with authorities in Bariloche and Villa La Angostura—less than 100 kilometers to the north—to warn them that seismic activity was becoming stronger and more frequent, one of the few tell-tale signs scientists have of an impending volcanic eruption. Villarosa told them the eruption was imminent and urged the drafting of a contingency plan. But it didn’t happen.

“You want the community to be prepared to face a catastrophe,” says Villarosa. He gives me an example: “When volcanic ash falls, the first service to go is electricity. Power lines and electrical towers get covered and since ash is a conductor, they short-circuit. This happened in Bariloche and Villa La Angostura and this has both an economic and a psychological cost. There are thousands of uncertainties and the people don’t feel protected.”

In the days following the eruption, people were advised by local health officials to wear face masks and stay indoors as more than a foot of ash settled on the region like a blanket of gray snow. The health risk was immediate: volcanic ash contains crystalline silica, a fine powder chemically similar to glass. Inhalation or contact with the skin and eyes produces irritation, which can especially exacerbate pre-existing respiratory conditions like chronic bronchitis, emphysema and asthma.

Over the next few days, the sunshine returned and the slow process of cleanup began. Downed power lines were replaced, collapsed roofs fixed, the roads plowed of pumice. But the region’s lakes, rivers and flora were all still shrouded in gray ash. What kind of environmental effect would this lasting layer of ash have?

One scientist seeking anwers is Gonzalo Irisarri at the University of Buenos Aires (UBA). Analyzing satellite images that show the extent of ash coverage on vegetation, Irisarri estimates that plant productivity in the region is at its lowest in 10 years. He explained the mechanics in a study published by UBA’s agriculture department in February: “The ashes deposited on the leaves act like an umbrella, they reduce the quantity of solar radiation a plant can absorb. This reduces photosynthesis, and consequently, the plant’s growth.”
But what did this mean for Patagonian flora?

“In these areas there is little agriculture. It’s mostly pastureland and natural steppes,” Irisarri says. The loss is to the sheep raised on that land, he says, and there have been many deaths. He points to one large sheep farm—or estancia—that lost 4,000 of the 27,000 head it had in 2011. The ranchers were fortunate to be able to move their herd to regions free of ash. Many subsistence sheep farmers weren’t as lucky. Irissari heard many accounts of devastating losses at smaller estancias.

The Puyehue-Cordón Caulle volcanic complex is still logging seismic activity, intermittently spewing bouts of ash. The February day I pulled into Bariloche, the ash cloud was heavy, obscuring the midday sun and cutting off the view to Lake Nahuel Huapi like a translucent curtain. Stepping off the bus, I asked the driver if my entire stay in Bariloche would be like this. “It’s been like this for seven months,” he said. “Just pray for the winds to blow it away.”

It’s a prayer the region’s tourism industry are relying heavily on. From the time of the eruption in June to the end of 2011, Bariloche—a winter and summer resort city that regularly draws more than 700,000 visitors a year—saw a huge drop in tourism. Over those gloomy months, its hotel occupancy rate was “practically null,” according to a report released by Bariloche’s Agrupación de Hosterías, Hoteles, Cabañas y Bungalows (AHHB, or Hotels, Inns, Cabins and Bungalows Association).

In August of 2011, three months after the initial eruption, the Argentine congress reached out a helping hand to affected businesses by voting to extend payments to their next productive season. With the reopening of the region’s main airport in December—closed on and off for months for repairs and because of the ash cloud—Bariloche saw a slight rebound in tourism: occupancy for January recovered to around 25%, according to the AHHB.

Chilean scientists say the Puyehue-Cordón Caulle complex is finally showing signs of letting up. The lava has stopped flowing and the ash has slowed to a faint wisp. Chilean evacuees have moved back to their mountain homes to resume life in the shadow of volcanoes.

Originally published in Spanish at Science Friday.

Photos by Marcos Radicella and Gustavo Villarosa & Valeria Outes