April 15, 2004

A swarm of seismic activity heralding renewed eruptive activity at Anatahan
Volcano in the Commonwealth of the Northern Mariana Islands (CNMI), which
began early on March 31st, has prompted the U.S. Geological Survey to
notify the National Oceanic and Atmospheric Administration's Washington
Volcanic Ash Advisory Center of volcanic activity that could be hazardous
to aircraft.

The swarm of very small earthquakes was the third and largest such episode
of activity since the eruption in May-August, 2003. The current round of
seismic intensity peaked on April 6th with approximately one small
earthquake each minute and was similar in nature to that observed at other
volcanoes before they erupted. On Sunday, new lava was spotted forming a
short flow or dome inside Anatahan's crater. Although the rate of
seismicity has declined since the April 6th peak, earthquakes are still
occurring frequently, and steam and ash emissions and small explosions are
likely to occur. Anatahan is continuously monitored by the CNMI Emergency
Management Office on Saipan and by USGS volcanologists in Hawaii,
Washington, and California, using Internet and wireless technology to
continuously track the situation as it develops.

Within the CNMI, nine active volcanoes pose a significant hazard to air
traffic and to planned settlement and economic development of many of the
islands. The CNMI Emergency Management Office (EMO) and the USGS have
developed a plan to evaluate and assess volcanic hazards, and to install,
maintain, and operate a volcano-monitoring network across the nine active
volcanoes to provide early warning of hazardous volcanic activity to
commercial and military aviation interests, the inhabitants of the islands,
the government of CNMI, and the public. Continued monitoring is needed so
that potential hazards to air traffic, existing communities, and future
island settlements from future eruptive activity can be quickly and
correctly assessed.

Volcanic eruptions pose a serious threat to aviation, but one that can be
mitigated through the combined efforts of scientific specialists, the
aviation industry, and air-traffic control centers. Eruptions threaten
aviation safety when finely pulverized volcanic material ("ash") erupts in
large airborne clouds which cover long distances at airliner cruising
altitudes. When an aircraft flies into an ash cloud results can include
degraded engine performance (including loss of thrust power), loss of
visibility, and failure of critical navigational and operational
instruments. The best safety strategy is for aviators to know the
locations of ash clouds and avoid them. Because ash clouds drift with
prevailing winds for many days and thousands of miles, they potentially
threaten air corridors that are far removed from the erupting volcano. For
example, each year approximately 25,000 large commercial passenger jets fly
through a small area of airspace immediately surrounding the Mariana
Islands, and more than 1 million planes fly from Asia to Australia and New
Zealand. On May 23, 2003, Anatahan produced an ash cloud that disrupted
regional and international air traffic on at least two days.

The volcanic-ash hazard to aviation is the subject of the upcoming 2nd
International Conference on Volcanic Ash and Aviation Safety in June in
Alexandria, VA. Information about the conference is available online at
http://www.ofcm.gov/homepage/text/spc_proj/volcanic_ash/about.html