Volcano Watch — Alaskan volcano sends ashy plumes thousands of feet into the air

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Augustine makes up a small (only 5 miles long by 7 miles wide), uninhabited island in the southern part of Cook Inlet, about 125 miles southwest of Anchorage. The volcano has experienced 6 significant eruptions since the early 1800s, the last time in 1986. Most eruptions have started with an explosive phase that lasts up to several weeks, followed by an extrusive phase in which sticky lava oozes from the summit and forms a dome.

Because of its location near major air traffic routes across the northern Pacific, ash from Augustine can be extremely hazardous to airplanes. When ash is sucked into a jet engine, it can melt and cause the engine to fail. An airplane-ash encounter during the eruption of Redoubt Volcano, Alaska, in 1989, caused a 747 aircraft carrying 231 passengers and 14 crew members to lose power to all four engines. The plane dropped over 2 miles in altitude to a mere 13,000 feet above the ground (only 2,000 feet above the mountains) before the engines were restarted and the plane landed safely in Anchorage. The damage to the aircraft amounted to more than $80 million. Clearly, it is important to detect such ash clouds before they can pose serious threats to aircraft, especially in the heavily traversed north Pacific.

In addition, Augustine has a tendency to collapse in major landslides into the ocean and create small, but potentially hazardous, tsunami waves. In the last 2,200 years, Augustine has collapsed at least 13 times. The most recent collapse was in 1883, when a 20-foot-high tsunami swept the shores of Cook Inlet. Fortunately, few people lived along the shore of the Inlet at that time, and no one was injured by the tsunami. Today, there are many homes and resorts on the water's edge that would be affected by a similar event.

The hazards posed by tsunamis and airborne ash make monitoring Augustine extremely important. Consequently, the Alaska Volcano Observatory (AVO) maintains a network of seismic and deformation equipment on the island.

In mid-summer 2005, AVO detected increased earthquake activity, a sign that Augustine was awakening from over two decades of slumber. At about the same time, GPS instruments on the volcano showed signs of inflation as magma began to accumulate beneath the surface. By December 2005, small steam explosions occurred as the rising magma encountered groundwater within the volcano. Finally, on January 11, 2006, two large explosions signaled the arrival of magma at the surface.

Additional explosions took place on January 13, 14, 17, 27, and 28, some sending ash as high as 50,000 feet above sea level. These eruptions caused some airplanes to divert from their routes, while other flights were canceled entirely. Then, late on January 28, the volcano entered a period of nearly continuous ash emission, with an ashy plume rising from the volcano's summit to 15,000 feet for almost two weeks straight.

If the volcano follows the pattern set by its past eruptions, the explosive phase will soon end, and lava will appear at the surface. The growth of the lava dome may be relatively calm and last for months. Lava domes are notorious, however, for exploding without warning; therefore it is important to keep a watchful eye on Augustine's current eruption.

The Hawaiian Volcano Observatory is contributing to the Augustine eruption response by sending volcanologists to assist the AVO staff. The exchange of scientists between volcano observatories is a common practice within the U.S. Geological Survey Volcano Hazards Program. It ensures that volcanologists at all of the observatories gain experience in both how volcanoes work and how to manage volcanic crises. This experience can be applied to future eruptions around the world, including any new activity that might occur right here in Hawai`i.

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Volcano Activity Update

During the past week, Kīlauea Volcano has remained at an elevated level of activity at the summit. The number of earthquakes located beneath the upper east rift zone of Kīlauea, between Lua Manu and Pauahi Craters, remains at moderate levels. Inflation of the summit caldera continues at the accelerated rate started on January 12.

Eruptive activity at Pu`u `O`o continues. On clear nights, glow is visible from several vents within the crater and on the southwest side of the cone. Lava continues to flow through the PKK lava tube from its source on the flank of Pu`u `O`o to the ocean, with scattered surface flows breaking out of the tube. In the past week, flows were active intermittently above the pali at the 2,300-ft elevation, on the slope of the pali, and on the coastal plain about 2 km inland of the ocean at Kamoamoa. The PKK lava tube, however, has had few breakouts in recent days, and very little surface lava has been visible at night on the pali.

As of February 9, lava is entering the ocean at East Lae`apuki, in Hawai`i Volcanoes National Park. The active lava bench continues to regrow following the major collapse of November 28. Access to the ocean entry and the surrounding area remains closed, due to significant hazards. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

There were two earthquakes beneath Hawai`i Island reported felt within the past week, both in the same area about 5 km (3 miles) southeast of Kīlauea summit at a depth of 3 km (2 miles). A magnitude-2.1 earthquake occurred at 3:05 p.m. on Saturday, February 4, and a magnitude-3.1 earthquake occurred at 11:28 a.m. on Wednesday, February 8.

Mauna Loa is not erupting. During the past week, earthquake activity remained low beneath the volcano's summit. Inflation continues, but at a rate that has slowed since early October 2005.