Volcano Watch — USGS sends team to assess eruption hazards in Papua New Guinea

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In early August, Pago volcano, on the central coast of New Britain Island, suddenly began exploding rocks and volcanic ash into the air. Thousands of nearby residents quickly left their homes and work to escape possible injury or death.

This week as many as 10,000 people are still evacuated from the immediate area around Pago. Sporadic explosions, ashfall, and an erupting lava flow are clear signs that the volcano is not yet finished.

Pago can produce large explosive eruptions that would endanger as many as 30,000 people within 30 km (19 miles). Scientists are now establishing the first ever monitoring network on the volcano, even while it erupts unpredictably! Volcano monitoring is desperately needed to track the volcano's activity and assess the possibility of more intense and more hazardous activity.

A team of experienced scientists from the U.S. Geological Survey's (USGS) Volcano Disaster Assistance Program is now in Papua New Guinea working with colleagues from Rabaul Volcano Observatory. Headquartered at the USGS Cascades Volcano Observatory in Vancouver, Washington, the program supports the only dedicated rapid volcano-response team in the world.

The program was established following a volcanic disaster in Colombia in 1985 that killed more than 23,000 people. In the middle of the night, a series of fast-moving debris flows swept down valleys leading from ice-capped Nevado del Ruiz volcano during a moderate-sized explosive eruption. This tragedy prompted the U.S. Agency for International Development, Office of Foreign Disaster Assistance, to ask the USGS to create a program to reduce fatalities and economic losses in countries experiencing a volcano crisis.

Since its inception in 1986, the Volcano Disaster Assistance Program has responded to 21 major volcano crises in the world and built volcano-monitoring infrastructure in nine countries. This effort has saved tens of thousands of lives and hundreds of millions of dollars in property.

The USGS and Rabaul teams are now actively installing a small network of three or four seismometers to track Pago's earthquake activity. Also, several continuously recording GPS receivers will help to determine the extent and rate of ground deformation due to magma movement.

The USGS team's work on Pago volcano is turning out to be one of its most challenging. The area is extremely rugged and thickly carpeted with rain forest, roads are lacking, helicopter availability is limited, and the volcano is producing sporadic explosions. The team has no way of knowing if the explosions will get larger or not, but geologic studies indicate Pago is clearly capable of producing much larger and more dangerous eruptions.

Pago is the active vent of a large volcano known as Witori caldera-a collapsed crater that formed during an extremely large explosive eruption about 3,300 years ago. The caldera is 11 km (7 miles) long and 6 km (3.5 miles) wide, with crater walls as high as 500 m (1,650 feet). Pago is a cinder cone about 250 m (820 feet) high located near the center of the caldera.

Witori caldera has produced at least 10-12 large explosive eruptions in the past 5,600 years, most recently less than about 500 years ago. The five largest of these events erupted between 6 km3 (1.4 mi3) and 30 km3 (7.2 mi3) of fragmented lava and pumice-up to four times the volume of material erupted in 1991 from Mount Pinatubo in the Philippines.

Unlike the fluid basalt lava erupted from Hawaiian volcanoes, lava from Pago is about a million times more viscous, resulting in stubby lava flows only a few kilometers (miles) long. Pago has erupted at least eight thick lava flows during its 350-500-year-old history.

The only historical eruption of Pago occurred between 1911 and 1933. This prolonged activity produced a thick, 5-km-long (3-mile) lava flow and intermittent explosive activity that culminated in a significant explosive eruption in 1933. The activity led to widespread displacement of people living in the area and famine from the destruction of native gardens by ashfall.

Volcano Activity Update

Eruptive activity of Kilauea Volcano continued unabated at the Pu`u `O`o vent during the past week. Molten lava is flowing near the end of the Chain of Craters road, and the National Park Service is allowing visitors to get up close to the action. The lava delta at Wilipe`a continues to grow, and lava is now also entering the ocean intermittently near West Highcastle.

One earthquake was reported felt during the week ending on September 19. Residents of Leilani Estates and Lanipuna Gardens subdivisions felt an earthquake at 1:37 a.m. on Wednesday, September 18. The magnitude-2.3 earthquake was located 4 km (2.4 mi) beneath Pu`ulena Crater.