A VOLCANO in Papua New Guinea is threatening to erupt and put thousands of lives at risk. Pago volcano has been slowly pumping out lava and intermittently spewing rocks and ash for more than two months, and 15,000 people have been evacuated. But scientists fear the worst may be yet to come.
鈥淭his activity could lead to something larger,鈥� says Dan Miller, chief of the US Geological Survey鈥檚 Volcano Disaster Assistance Program, which has sent an emergency team to monitor the situation. Pago has erupted at least eight times in the past 500 years, most recently in 1933. That eruption forced many people from their homes, and sparked a famine. But Pago is merely the active vent of Witori crater or 鈥渃aldera鈥�, a much larger, more dangerous type of volcano with the potential for enormous eruptions. A large explosion could send massive flows of hot ash and debris up to 30 kilometres away, endangering up to 30,000 people, and would temporarily change the Earth鈥檚 climate.
During the past 5600 years, the caldera has erupted more than 10 times, sometimes ejecting four times as much material as Mount Pinatubo in the Philippines did when it exploded in 1991. Witori鈥檚 last big show was just under 500 years ago, and scientists are worried that the caldera could be due for another big event.
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The three USGS geologists, flown in last month at the request of the Papuan government, are now working with local researchers to set up a seismic and GPS monitoring network around the volcano. This will help in forecasting more explosive eruptions by recording the small earthquakes and ground swellings heralding most eruptions. A small amount of ground deformation near Pago would presage a minor eruption. 鈥淏ut if deformation were to become more widespread, we鈥檇 worry about larger eruptions,鈥� says Miller.
The mission is proving to be one of the team鈥檚 most difficult so far. There are few roads or trails and some areas are only accessible by helicopter. 鈥淟ogistically, it鈥檚 been challenging. It鈥檚 a rugged, densely vegetated jungle out there,鈥� says Miller. And working on an active volcano is always a little unnerving, he adds. Very large caldera-forming eruptions are rare and none has ever been monitored, so the scientists don鈥檛 know exactly what to expect. But the signs should be similar to those recorded by the team before the smaller Pinatubo eruption.
Once the network is in place, geologists from the nearby Rabaul Volcano Observatory will monitor Pago and Witori and help local authorities decide when it is safe for evacuees to return or if more people should leave. But their measurements will give hours or days notice of an eruption at best.
Earlier this year, 快猫短视频 reported on a simple monitoring programme that could give months of warning (3 August, p 17). Developed by Hazel Rymer and Joachim Gottsmann at the Open University in Milton Keynes, the method involves monitoring changes in gravity and ground height within the caldera. 鈥淚t tells you way before any other precursors whether dangerous activity is on the way,鈥� says Gottsmann.
Rymer told 快猫短视频 that local geologists at Rabaul have been begging her team to come out for months. But neither Rymer鈥檚 team nor the Rabaul observatory had the money to fund the trip, and she says it is probably now too late, since the deep structural changes her method monitors occur months or years before any surface movements are felt.
Miller agrees that taking gravity measurements could have helped predict the volcano鈥檚 activity, but says his priority now is to set up a seismic monitoring network as quickly as possible. Meanwhile 15,000 people wait anxiously for word that it is safe to return home.
