Summer 2002 Field Plans: Volcano-monitoring and geologic investigations by the Alaska Volcano Observatory

As part of an ambitious, multi-year volcano-monitoring expansion effort, this summer scientists of the Alaska Volcano Observatory (AVO) will increase the number of volcanoes they monitor with real-time geophysical instruments and continue geologic studies of several volcanoes in order to decipher their eruptive histories and identify potential hazards from future eruptions. AVO scientists come from the three agencies in the formal partnership - the United States Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophyscial Surveys. Okmok Volcano (left), a spectacular 10-km-wide caldera on Umnak Island that erupted most recently in 1997, will become the 25th historically active volcano on which AVO will install telemetered monitoring instruments since the observatory was formed in 1988. Last summer, scientists installed a seismic network on Mount Veniaminof and added stations to Mount Wrangell volcano. Explosive eruptions from Alaskan volcanoes generate clouds of ash that pose a hazard to aircraft flying along the North Pacific air routes (see background below).

When AVO was established in 1988, only Augustine Volcano, 275 km (170 miles) southwest of Anchorage, was monitored well enough for scientists to provide effective warning of an impending eruption. By the end of 2000, 22 volcanoes located as far as 2,050 km (1,275 miles) from Anchorage were monitored with 129 seismic stations. AVO scientists also have recently developed the capability to analyze meteorological satellite data to detect hot areas on volcanoes and eruption clouds of volcanic ash blown downwind from an erupting volcano (right). Satellite data is routinely analyzed two times every day and more frequently during periods of unrest or eruption.

The hard and often risky work of many people affiliated with AVO has proven that the remote and dangerous volcanoes in Alaska can indeed be successfully monitored to reduce risk to people and property. Today's challenging plans will make the monitoring program even more robust and improve our understanding of this awesome volcanic chain.

Overview of 2002 field plans by volcano

Akutan Volcano, Akutan Island
Most recent eruption: March-May 1992; seismic swarm in March 1996

Beginning in mid June, a team of scientists will deploy a telemetered GPS monitoring network on Akutan Volcano. The new installations will compliment the existing GPS network, which is surveyed intermittently. Scientists will also install several state-of-the-art seismic sensors to augment the seismic network, which was installed in 1996.

A large explosive eruption about 1,600 years ago resulted in the formation of the present 2-km-wide caldera. At least 27 different eruptive events have occurred since A.D. 1790, all from the 200-m tall cinder cone in the northeast part of the caldera. For information about the potential volcano hazards from Akutan, see the volcano-hazard assessment published in 1998.

Mount Veniaminof volcano, Alaska Peninsula
Most recent eruption: 1993-1995

Scientists will return to Mount Veniaminof volcano from mid-July to mid-August to continue their geologic mapping of this massive ice-filled caldera and, if necessary, service seismic stations that were installed last summer (right photo). In addition to geologic mapping, a campaign-style GPS survey is planned.

A large explosive eruption of Veniaminof about 3,700 years ago resulted in a caldera about 10 km in diameter. Today, the caldera is largely filled with ice. Geologists will focus their attention on volcanic deposits erupted in the past 10,000 years, especially on those emplaced during the most recent caldera-forming eruption, by recording the location and sequence of volcanic ash layers erupted by Veniaminof and other Alaskan volcanoes. Also, they'll look for evidence of eruptions that interacted with ice and snow; for example, lava flows emplaced beneath a thick layer of ice and snow or eruptions of hot lava fragments that subsequently eroded and melted enough snow and ice to form lahars (volcanic debris flows). Okmok Volcano, Umnak Island
Most recent eruption: February 1997

In July and August, scientists will work on Okmok volcano to install a real-time monitoring network including traditional seismic instrumentation, 4 new modern seismic sensors, and telemetered GPS receivers. For the third year, scientists will continue to unravel the volcano's eruptive history by mapping layers of volcanic deposits erupted during the past tens of thousands of years. Okmok is one of the more active of Aleutian volcanoes and erupted most recently in 1997. The activity erupted a large `a`a lava flow in the caldera and eruption clouds (photo courtesy of John Sease, NOAA National Marine Mammals Laboratory) that reached as high as 20,000 feet above sea level, dusting nearby Ft. Glenn Ranch with gritty basaltic ash.

In 2001, AVO geologists identified volcanic layers (right) formed by the explosive interaction of water and erupting magma. The deposits shown in the photograph are located atop Cone C, one of several prominent vents within Okmok's caldera. Geologists also found evidence for the interaction between lava and ice in the caldera during past eruptions. Work this summer will focus more on these deposits.

Okmok volcano has experienced at least two massive caldera-forming eruptions in the last 10,000 years, the most recent about 2,000 years ago. Continued basaltic eruptions from within the caldera have produced a variety of volcanic landforms including cinder cones, lava flows, and explosion craters. As at Aniakchak Caldera on the Alaska Peninsula, Okmok Caldera also contained a large lake sometime after its most recent caldera-forming; this lake drained later catastrophically to form an enormous flood fan reaching all the way to the sea.

Aniakchak Caldera, Alaska Peninsula
Most recent eruption: May 1931

In mid July, a small team of scientists will visit Aniakchak volcano to service the network of seismic stations installed there in 1998 and focus on recently erupted volcanic deposits. Based on several years of geologic mapping studies of the caldera, a hazard assessment for Aniakchak Volcano was released in 2001 (reference available online).

Cleveland Volcano, Chuginadak Island
Most recent eruption: February-March 2001

In late June or early July, two geologists will visit Cleveland volcano in order to gather data for a geologic reconnaissance map and study the lava flow and tephra erupted in 2001. Last summer, AVO scientists were the first geologists ever to visit the island. They spent a total of about 8 hours sampling a few volcanic rocks, including the 2001 lava flow, and deploy a temporary seismic station. At least one earthquake was recorded during their stay.

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Background - Expanding the program of the Alaska Volcano Observatory

Alaska is home to one of the most formidable volcanic chains on Earth. More than 100 volcanoes extend westward 2,500 km (1,550 miles) from Cook Inlet near Anchorage to the Aleutian Islands and eastern Russia. In Alaska, over 40 volcanoes have erupted at least once in the past 240 years. Many eruptions and periods of unrest at Alaskan volcanoes in the past 15 years have affected cities and remote communities; the oil, power, and fishing industries; and, most importantly, commercial aircraft in the heavily traveled North Pacific air routes. For example, in 1998 more than 20,000 passengers and millions of pounds of cargo were being transported daily over these routes, including more than 90% of the all-cargo flights between Asia and North America.

Volcanoes monitored with seismic networks, 2001

In the next several years, AVO scientists are planning to install seismic networks on at least five more volcanoes in the westernmost Aleutian Islands in addition to continued expansion in the central Aleutians. Targeted volcanoes include Kiska, Gareloi, Tanaga, Mount Peulik, Korovin, Chiginagak, Little Sitkin, and Semisopochnoi (Mount Cerebus).

Why such a focused effort to monitor Alaskan volcanoes?

In 1989, volcanic ash from the eruption of Redoubt Volcano nearly downed a 747-400 jumbo jet carrying 231 passengers. On December 15, the plane unknowingly descended into an eruption cloud 240 km (150 miles) downwind from the volcano, losing power in all four engines as gritty ash and sulfurous gas filled the aircraft. After gliding powerless for eight frightening minutes and falling 4,450 m (14,600 feet) toward the rugged Talkeetna Mountains, disaster was barely averted when the pilots restarted the engines and landed safely in Anchorage. Repair costs of the jet exceeded $ 80 million.

The impact of Redoubt's eruption on aircraft safety ushered in a new era of volcano monitoring in Alaska. Since 1989, AVO scientists have worked closely with the aviation industry and other federal agencies to help aircraft avoid volcanic ash and sulfur aerosols that can drift high in the atmosphere far downwind from an erupting volcano.

The key to reducing risk to aircraft was for AVO to increase the number of monitored volcanoes so that reliable warnings of impending activity could be given and the status of an ongoing eruption accurately determined. In 1996, with Congressional funding provided through the Federal Aviation Administration (FAA), AVO scientists began an aggressive effort to expand the monitoring program to active volcanoes in the Aleutian Islands.

Because of the remote locations of these volcanoes, AVO scientists have also built a very successful remote-sensing program using meteorological satellite sensors. All volcanoes in Alaska and Kamchatka are analyzed at least twice daily for signs of activity using images from several satellites. AVO is the only observatory that routinely integrates near-real-time satellite data with traditional ground-based techniques to detect unrest and eruptions for so many volcanoes.

AVO is a formal partnership between the United States Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.