REDUCING THE RISK FROM VOLCANO HAZARDS

UNITED STATES GEOLOGICAL SURVEY

Volcanic Ash—Danger to Aircraft

in the North Pacific

The world’s busy air traffic

corridors pass over

hundreds of volcanoes capable of sudden, explosive

eruptions. In the United States

alone, aircraft carry many

thousands of passengers and

millions of dollars of cargo

over volcanoes each day.

Volcanic ash can be a serious

hazard to aviation even thousands of miles from an eruption. Airborne ash can diminish visibility, damage flight

control systems, and cause jet

engines to fail. USGS and

other scientists with the

Alaska Volcano Observatory

are playing a leading role in

the international effort to

reduce the risk posed to

aircraft by volcanic eruptions.

As the crew of KLM Flight 867 struggled

to restart the plane’s engines, “smoke” and a

strong odor of sulfur filled the cockpit and

cabin. For five long minutes the powerless 747

jetliner, bound for Anchorage, Alaska, with

231 terrified passengers aboard, fell in silence

toward the rugged, snow-covered Talkeetna

Mountains (7,000 to 11,000 feet high). All four

engines had flamed out when the aircraft inadvertently entered a cloud of ash blown from

erupting Redoubt Volcano, 150 miles away.

The volcano had begun erupting 10 hours earlier on that morning of December 15, 1989.

Only after the crippled jet had dropped from

an altitude of 27,900 feet to 13,300 feet (a fall

of more than 2 miles) was the crew able to

restart all engines and land the plane safely at

Anchorage. The plane required $80 million in

repairs, including the replacement of all four

damaged engines.

Such dangerous and costly encounters between aircraft and volcanic ash can happen

because ash clouds are difficult to distinguish

from ordinary clouds, both visually and on

radar. Also, ash clouds can drift great distances

from their source. For example, in less than 3

days, the ash cloud from the June 15, 1991,

eruption of Mount Pinatubo in the Philippines

traveled more than 5,000 miles to the east coast

of Africa. This ash cloud damaged more than

20 aircraft, most of which were flying more

than 600 miles from the volcano.

Along North Pacific air routes, some of the

busiest in the world, at least 15 aircraft (including KLM Flight 867) have been damaged

since 1980 by flying through volcanic ash

clouds. In the same period, there have been 80

such encounters worldwide, causing hundreds

of millions of dollars in damage and lost revenue. Fortunately, no fatalities have yet occurred,

but the growth in air traffic over volcanically active regions, such as the North Pacific, is increasing the chance of a deadly encounter.

More than 10,000 passengers and millions

of dollars in cargo fly across the North Pacific

region each day, and the area’s aviation traffic

is increasing about ten percent a year. This region also contains one of the most active parts

of the “Ring of Fire,” a belt of active volcanoes that borders much of the Pacific Ocean.

About 100 potentially dangerous volcanoes lie

under air routes in the North Pacific. Along

During a 1989–90 series of eruptions, Redoubt Volcano, Alaska, spewed enormous clouds of ash.

Ash blown from this volcano on December 15, 1989, nearly caused a 747 jetliner (KLM Flight 867)

carrying 231 passengers to crash. Partly in response to this near-fatal incident, the U.S. Geological

Survey organized the first International Symposium on Volcanic Ash and Aviation Safety. This 1991

conference in Seattle, Washington, focused attention on ways to reduce the risk volcanic ash poses

to the world’s rapidly increasing air traffic. (Photo courtesy of Joyce M. Warren.)

Mount Spurr. Photo shows an Alaska

Volcano Observatory scientist installing a

seismometer near Mount Spurr (in

background). (Map by David Schneider,

Michigan Technological University.)

Several times during the summer of 1992, ash clouds from explosive eruptions at Mount Spurr volcano,

Alaska, significantly disrupted air traffic across the United States and Canada. In August, ash fall from

one of these eruptions shut down Anchorage International Airport for 20 hours. The map (composite

satellite image) shows the movement of the ash cloud from the September 16–17, 1992, eruption of

9/20/92

9/20/92

9/19/92

9/19/92

9/18/92

9/18/92

9/17/92

9/17/92

9/17/92 Mt. Spurr
U.S. DEPARTMENT OF THE INTERIOR • U.S. GEOLOGICAL SURVEY

For more information contact:

Alaska Volcano Observatory (907) 786-7443

4200 University Drive

Anchorage, AK 99508

http://www.avo.alaska.edu/

See also What are Volcano Hazards? (USGS Fact

Sheet 002-97)

U.S. Geological Survey Fact Sheet 030-97

1997

COOPERATING ORGANIZATIONS

the Alaska Peninsula and the Aleutian Islands

there are more than 40 historically active volcanoes. Even greater numbers of active volcanoes are found to the west of Alaska on the

Russian Kamchatka Peninsula and in the

Kurile Islands.

Each year about 5 eruptions occur along

the 2,400-nautical-mile arc from Alaska to the

Kuriles. Ash clouds from volcanoes in this

segment of the “Ring of Fire” are usually carried to the east and northeast, directly across

busy air routes. On an average of 4 days a year

in the North Pacific region, volcanic ash is

present above an altitude of 30,000 feet, where

most large jet aircraft fly.

In 1988, in part to address the hazard posed

by airborne volcanic ash in the North Pacific,

the U.S. Geological Survey (USGS), in cooperation with the University of Alaska Fairbanks

Geophysical Institute and the Alaska Division

of Geological and Geophysical Surveys, established the Alaska Volcano Observatory

(AVO) with offices in Anchorage and

Fairbanks. AVO provides hazard assessments,

updates, and warnings of volcanic activity in

Alaska and is regularly consulted by government agencies, airlines, and the public. AVO

scientists also play a key role in monitoring

eruptions and tracking ash clouds from volcanoes in the Russian Far East as part of a formal working relationship with the Russian

Academy of Science’s Kamchatkan Volcanic

Eruptions Response Team (KVERT).

Accurate forecasts of volcanic eruptions are

one way to help pilots avoid flying through

ash clouds. To provide these essential early

warnings, AVO operates networks of seismometers to detect earthquakes beneath volcanoes.

Such quakes commonly mark the beginning

of the unrest that can lead to eruptions. Recent supplemental funding from the Federal

Aviation Administration (FAA) has made possible the tripling of the number of Alaskan volcanoes monitored by seismic networks. By late

1997, AVO expects to be operating such networks at 16 of the most dangerous volcanoes

in Alaska.

AVO scientists also examine satellite data

and work closely with the National Weather

Christina A. Neal, Thomas J. Casadevall,

Thomas P. Miller, James W. Hendley II,

and Peter H. Stauffer

Graphic design by

Sara Boore and Susan Mayfield

Service to detect and track volcanic ash plumes

in the North Pacific region. Other elements of

the observatory’s monitoring program include

periodic observational overflights of the 40

potentially active Alaskan volcanoes. Some of

these flights measure sulfur dioxide and carbon dioxide gas emissions from the volcanoes,

as unusually high levels of these gases often

precede volcanic eruptions. Because a

volcano’s past behavior provides important

clues about possible future eruptions, AVO

scientists are also conducting on-site geologic

studies at Alaska’s volcanoes, collecting data

and samples for later analysis.

The monitoring techniques described

above have enabled AVO to anticipate several

Alaskan eruptions hours to weeks in advance,

including events at Redoubt Volcano (1989)

and Mount Spurr (1992). In September 1996,

newly installed seismometers at Pavlof Volcano, on the Alaska Peninsula, quickly detected the onset of an eruption, enabling AVO

to promptly alert the aviation community.

The successes of AVO are examples of the

North Pacific and Russian Far East air routes (gray lines) pass over or near more than a hundred potentially

active volcanoes (red triangles). Aircraft flying along these routes, some of the busiest in the world, carry more

than 10,000 passengers and millions of dollars of cargo each day to and from Asia, North America, and

Europe. In the North Pacific region, several explosive eruptions occur every year. Ash from these eruptions,

which has caused jet engines to fail, is usually blown to the east and northeast, directly across the air routes.

progress that can be achieved through cooperative efforts among various organizations.

The observatory’s work is making air travel

safer by closely monitoring volcanoes in the

North Pacific region and by rapidly alerting

the aviation community to potentially dangerous ash clouds. In addition to active participation in AVO, the ongoing work of the

USGS Volcano Hazards Program in the volcanically active regions of the United States,

including Alaska, Hawaii, Arizona, California,

and the Pacific Northwest, is helping to better protect people’s lives and property from

volcano hazards.

In 1989, the Alaska Volcano Observatory (AVO) developed a “color code” to rapidly and clearly communicate the likelihood of an eruption at potentially dangerous volcanoes. This format for summarizing the status

of a volcano has proven extremely effective in alerting the aviation community to potential ash hazards in

the North Pacific region.

Federal Aviation Administration

Institute of Volcanic Geology and Geochemistry,

Petropavlovsk, Kamchatka

Michigan Technological University

National Oceanic and Atmospheric Administration,

National Weather Service

Alaska Division of Geological and

Geophysical Surveys

Geophysical Institute, University of

Alaska Fairbanks

AVO LEVEL-OF-CONCERN COLOR CODE

C o olor I t ntensity of Unrest at Volcan Forecas

G . REEN V . olcano is in quiet, "dormant" state No eruption anticipated

Y ) ELLOW Small earthquakes detected locally and (or

increased levels of volcanic gas emissions.

An eruption is possible in the next few weeks and

may occur with little or no additional warning.

O . RANGE Increased numbers of local earthquakes

Extrusion of a lava dome or lava flows (nonexplosive eruption) may be occurring.

Explosive eruption is possible within a few days and

may occur with little or no warning. Ash plume(s) not

expected to reach 25,000 feet above sea level.

R t ED Strong earthquake activity detected even a

distant monitoring stations. Explosive eruption

may be in progress.

Major explosive eruption expected within 24 hours.

Large ash plume(s) expected to reach at least 25,000

feet above sea level.

A L A S K A

R U S S I A

J A P A N

Kamchatka Peninsula

Kurile I s lands

Aleutian Islands Alaska Peninsula

Anchorage

Fairbanks

Mt. Spurr Volcano

Redoubt Volcano

Pavlof Volcano

150

180°

°W

150°E

60°N

50°N

40°N

120°E