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LEVEL OF CONCERN COLOR CODE: ORANGE
LAST LEVEL OF CONCERN: ORANGE
A low-level eruption continues at Pavlof Volcano on the Alaska Peninsula. During the past week, periods of increased seismicity are interpreted to correlate with eruption of ash and bombs several hundred to perhaps 1,000 feet above the summit of the cone. Satellite imagery obtained over the past 24 hours, however, has detected no ash cloud in the vicinity of the volcano. Visual observations of the volcano continue to be hampered by poor weather.
Since the late 1700's, nearly 40 separate eruptions of Pavlof Volcano are known to have occurred, making Pavlof one of the most active volcanoes in Alaska. Recent eruptions have been characterized by an early explosive event that can propel ash to an altitude of over 10 km (33,000 feet) above sea level. The eruptions then proceed as intermittent, low-level Strombolian activity with ejection of fluid lava spatter and small amount of ash and incandescent bombs to heights of usually less than 1,000 feet above the cone. Spatter-fed lava flows and ash-rich mudflows can also result from the accumulation of hot material on the steep flanks of the volcano. This kind of low-level activity could continue for many months,
punctuated by occasional more explosive events.
Pavlof is located 600 miles southwest of Anchorage on the Alaska Peninsula. The nearest towns to the volcano are Cold Bay (37 mi SW), King Cove (30 mi SW), Sand Point (60 mi E), and Nelson Lagoon (50 mi NE). These towns could expect light ash fall depending on wind direction and level of eruptive activity. Mudflows and some flooding could occur in the Cathedral River valley north of the volcano. The hazard to aircraft from airborne ash may be considerable if a large explosive event occurs, however during the more characteristic low-level activity currently in progress, this hazard is minor.
AVO maintains a six-station seismic network near the volcano. Until further notice, we are maintaining 24-hour staffing at the Observatory to monitor the situation.
AVO received a pilot report on Wednesday of a small ash plume above Amukta Volcano in the Central Aleutian Islands. There have been no further observations of eruptive activity at Amukta, and satellite images in the last 4 hours have not detected ash above the volcano.
Amukta is a poorly known, seismically unmonitored, and uninhabited island stratovolcano located about 230 miles east of Adak Island. It has erupted at least 5 times since 1760, most recently in 1987.
The seismic swarm that began on 1 August 1996 beneath
Mount Iliamna continued during the past week at an average rate of about 9 earthquakes per day. All events were within or just below the volcanic cone. Magnitudes of most earthquakes were less than 1.0. All earthquakes have been volcano-tectonic (VT); no long-period earthquakes or tremor that usually precede volcanic eruptions have been observed. This seismicity is likely related to an intrusion of magma beneath Iliamna Volcano. Such an intrusion does not mean an eruption is imminent.
Iliamna Volcano is a deeply dissected stratovolcano located 135 miles southwest of Anchorage. The frequency of eruptions from Iliamna Volcano is much less than other Cook Inlet volcanoes. Lahar (mudflows) deposits, perhaps only 300 years old, occur in several major river valleys near the volcano, in addition to large noneruption-induced landslide deposits. There is evidence of a major volcanic explosive eruption, perhaps 3,000 to 4,000 years ago. No historic eruptive activity has been documented at Iliamna Volcano. However, a prominent fumarole field located near the summit produces small steam plumes commonly visible from Anchorage and the Kenai Peninsula on clear days.
Seismic activity at Spurr, Redoubt, and Augustine volcanoes remains at normal background levels.
AVO maintains a computerized alarm system capable of
notifying AVO seismologists during non-business hours
should unusual seismic activity occur at Spurr, Iliamna,
Augustine, or Akutan volcanoes.
AVO continues to test new seismic networks at Pavlof,
Dutton, Makushin, Akutan, and Katmai area volcanoes.
Reports on these volcanoes will be added to the AVO weekly
update as data acquisition and analysis become reliable.
We anticipate that this will occur by mid-November.