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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 Alaskan Peninsula. On Tuesday, seismicity began to increase, indicating stronger eruption activity relative to the previous week. Visual observations and satellite data analyses, though hampered by poor weather, verified that increased seismicity can be correlated with eruption of ash and bombs several hundred to as much as 4,000 feet above the summit of the cone. On two occasions during the past week, satellite imagery has shown thin ash plumes as far as 45 km (30 miles) from the volcano.
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.
No further reports have been received regarding activity at Amukta Volcano in the Central Aleutian Islands.
The seismic swarm that began on 1 August 1996 beneath
Iliamna Volcano continued during the past week at an average rate of about 7 earthquakes per day. All events were beneath the volcanic cone. Magnitudes of most earthquakes were less than 1.0; maximum magnitude was 2.2. 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.
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 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.