Okmok Activity - Color Code YELLOW : Alert Level ADVISORY

Seismicity at Okmok volcano continues at low levels. Satellite views remain cloudy throughout the week.

Seismicity at Okmok volcano continues at low levels. There has been a small increase in seismic activity over the last few days. Satellite views remain cloudy throughout the week. An AVO field crew working on the volcano safely returned on Monday. They reported steaming, but not other eruptive activity. Work is underway processing the many rock and ash samples, gps data, and FLIR thermal cam data. They have posted some of their field photos to our website image database.

Seismicity at Okmok volcano continues at low levels. There has been a small increase in seismic activity over the last 24 hours. Satellite views remain cloudy throughout the week. An AVO field crew working on the volcano since Wednesday reported steaming, but not other eruptive activity. Although the level of seismicity has declined, it is possible for vigorous ash emissions to resume at any time. The AVO field crew repaired one seismic and one GPS station. They have also gathered ash samples, made visual observations, and photographed the volcano. They will be working at Okmok through September 15.

Seismicity at Okmok volcano remained low this week. Satellite views were obscured by clouds all week and we have no new visual observations. Significant ash plumes have not been observed since August 19.

Seismicity at Okmok volcano has declined and significant ash plumes have not been observed since August 19. The Aviation Color Code/Alert Level was reduced to YELLOW/Advisory on August 27. A clear satellite view on August 28 showed a weak steam plume and a weak thermal anomaly. Although the level of seismicity has declined and it appears that ash is no longer being erupted, it is possible for vigorous ash emissions to resume at any time.

Seismicity at Okmok Volcano has been steadily declining for the past eight days and significant ash plumes have not been observed since August 19. Therefore AVO is lowering the aviation color code from Orange to Yellow and the Alert Level from Watch to Advisory.

Volcanic unrest continues at Okmok Volcano. Satellite data from Monday, August 18, indicated intermittent small ash emissions which drifted generally to the south and reached no higher than 10,000 to 15,000 feet. Beginning Tuesday, August 19, the level of seismic activity approached pre-eruption levels and satellite data showed that ash was no longer being emitted. Despite mostly cloudy conditions on Thursday, August 21, satellite observations show a possible thermal anomaly at the volcano. Seismic activity stayed near pre-eruption levels the remainder of the week.

Eruptive activity continues at Okmok Volcano although the general intensity of the eruption has declined throughout the week. The seismic intensity and tremor duration are still above background levels suggesting that minor ash and steam emissions are still occurring.

Eruptive activity continues at Okmok Volcano on Umnak Island in the eastern Aleutian Islands. The intensity of activity has been relatively steady for the past week and ash plumes reaching 10,000 - 20,000 feet have been observed in satellite images and by local observers. Periods of intense seismicity are not necessarily corresponding with episodes of significant ash production and this has complicated attempts to provide early warning about potential ash cloud hazards based on seismicity alone. A crew of AVO scientists visited Umnak Island and viewed the eruption on August 2nd and 3rd. They report significant ash fall in the caldera and on the upper flanks of the caldera rim, lahars and lahar deltas forming in drainages from the southeast to northeast flanks, and a very vigorous eruption emitting continuous ash jets from three or more vents in the vicinity of Cone D in the northeast sector of the caldera.

The episode of strong volcanic tremor at Okmok that peaked at about 4:30 AKDT (12:30 UTC) has declined in intensity. Occasional bursts of tremor, lasting from 2-5 minutes are still occurring but these do not appear to be associated with large ash emissions reaching above 20,000 feet. Satellite and local observations indicate a lower level dark ash plume and a slightly higher steam plume. Although it remains possible for ash emissions to extend to 30,000 feet or higher, the overall trend of the seismicity suggests that lower level ash plumes will be more common.

Strong volcanic tremor has returned to Okmok. Tremor amplitudes began to climb at around 04:05 AKDT (12:05 UTC) and have remained high since. In the past, tremor of this amplitude usually indicates the potential for strong explosive activity with ash plumes exceeding 30,000 ft ASL. No satellite data collected since the elevated tremor began are currently available.

The eruption of Okmok volcano continues. Ash and steam plumes ranging in altitude from 10,000 to 35,000 feet have been observed continuously throughout the week, and intermittent light ash fall has occurred on parts of Umnak and Unimak Islands. From July 28 to July 30 the color code was increased to red in response to a vigorous eruptive episode. On July 31 a fishing boat located about 7 miles north of the volcano reported no visibility due to ash fallout. Seismic activity continues to be characterized by episodes of continuous and pulsating tremor that are strong enough to be seen clearly on networks of neighboring volcanoes. A small field crew of Alaska Volcano Observatory staff are currently in Unalaska to collect ash and pumice samples, make visual observations, and if possible service the seismic and geodetic network.

Satellite images and recent pilot reports indicate the ash plume at Okmok has decreased to altitudes between 15,000 and 20,000 ft and is moving west from the volcano. Seismicity continues to alternate between periods of continuous and pulsating tremor. The pulses continue to be identified on seismometers on Makushin Volcano on Unalaska Island. Based on these observations AVO is lowering the aviation color code at Okmok volcano to ORANGE and the Alert Code to WATCH. Stronger explosive activity could resume at any time with little or no warning.

Satellite images indicate ash may have reached 35,000 ft in a plume heading E to SE from the volcano. The intensity and duration of seismicity from the eruption at Okmok has changed from continuous tremor to a pulsating signal over the past 7.0 hours. These pulses are strong enough to be easily identified on seismometers on Makushin Volcano on Unalaska Island. Stronger explosive activity could resume at any time with little or no warning.

The amplitude and duration of seismic activity has decreased over the last five hours. Satellite data indicate ash is rising to 20,000 to 22,000 feet. Based on these observations AVO is decreasing the aviation color code at Okmok volcano to ORANGE, and the alert level to WATCH.

The amplitude of seismic activity has increased in the past hour. Two pilots report ash to 40,000 feet. Satellite data confirm ash to at least 35,000. Based on these observations AVO is increasing the aviation color code at Okmok volcano to RED, and the alert level to WARNING.

The eruption of Okmok Volcano continued throughout this week with persistent ash emissions rising from 15,000 to 25,000 feet. From July 19 to July 20 the color code was increased to red in response to a more vigorous eruptive episode which produced ash to 30,000 feet. Photographs and an overflight by Alaska Volcano Observatory staff on July 20 and 21 confirmed the existence of multiple vigorous vents on the caldera floor. Seismicity was characterized by intermittent bursts of volcanic tremor early in the week. This changed to continuous mid-level volcanic tremor on July 23, which persists to the current time. Amplitude of tremor has been generally constant since July 21. Although there has been little change in the eruption in the past several days, stronger explosive activity could resume at any time with little or no warning.

The aviation color code for Okmok Volcano has been lowered from RED to ORANGE. The volcano alert level has been lowered from WARNING to WATCH. The eruption of Okmok Volcano continues. Seismicity has changed from nearly continuous volcanic tremor to a more episodic character, and the overall seismic intensity has declined over the past 14 hours. The most recent satellite imagery indicates an intermittent ash plume is rising to 15,000 to 20,000 ft above sea level. Reports from pilots indicate a plume of ash and steam is reaching roughly 15,000 ft. above sea level. Stronger explosive activity could resume at any time with little or no warning.

Over the last 60 minutes, the amplitude of seismicity at Okmok Volcano has risen markedly, reaching a level commonly associated with vigorous ash emission. AVO believes that ash from Okmok could be exceeding 30,000 feet above sea level. For this reason, AVO is raising the aviation color code to RED and volcano alert code to WARNING.

The 2008 eruption of Okmok Volcano, which began on July 12 at 11:43 AKDT (19:43 UTC), continues. The initial phase of the eruption was quite explosive and produced a wet, ash and gas-rich plume that reached 50,000 feet above sea level. Wet, coarse (sand-sized) ash fall was reported within minutes of the eruption's start at Fort Glenn, about 10 km E/SE of Okmok Caldera. A light ashfall was also reported at Unalaska/Dutch Harbor by 13:00 AKDT. Based on pilot reports, airborne photographs, and radar intensity images, the eruptive vent appears to be new, having formed to the northwest of Cone D (located east of the center of the caldera). Over the last week, the severity of eruption has slowly declined. Pilot reports, seismicity, and satellite data all indicate that the eruption is now episodic, with occasional, ash-producing explosions occurring every 15 to 30 minutes. The plumes from these explosions appear to be limited to about 20,000 feet above sea level. The current Okmok eruption differs from eruptions of the recent past in two important respects: it has been considerably more explosive, and it has occurred in a different place. Prior to this eruption, and at least since the late 1800s, eruptive activity had been concentrated at Cone A, in the southwestern corner of the caldera, and had been limited to relatively low-level plumes, generally less than 30,000 feet above sea level. Because of these differences, it is not a simple matter to forecast the eventual course of the current eruption based on recent past experience. Over the next several weeks to months, intermittent explosions are likely to occur, and some of these may produce ash plumes to 30,000 feet above sea level. Lava fountaining and lava flows are also possible, although these will result in hazards confined mainly within the caldera. We also cannot rule out a return to more vigorous explosions, perhaps even exceeding the size of those on July 12.

The aviation color code for Okmok Volcano has been lowered from RED to ORANGE. The volcano alert level has been lowered from WARNING to WATCH. Okmok Volcano continues to erupt. Seismicity has changed from nearly continuous volcanic tremor to a more episodic character, and the overall seismic intensity has declined. The most recent satellite imagery indicates little or no ash, however weather clouds may be obscuring an ash signal.

Okmok Volcano continues to erupt. Over the last 24 hours, activity at Okmok has diminished. Seismicity has changed from nearly continuous volcanic tremor to a more episodic character, and over the last several hours, the overall seismic intensity has declined. The most recent satellite imagery indicates little or no ash, however weather clouds may be obscuring an ash signal. At 05:33 this morning AKDT (13:33 UTC), thermal satellite imagery revealed elevated surface temperatures in the northeast sector of the caldera. Because of continuing unrest and uncertainty about the immediate future of the eruption, Okmok remains at aviation color code RED and alert level WARNING. All areas immediately around the volcano are considered hazardous. Airborne ash and gas continue to pose a hazard to aviation in the area. Additional ash fall will likely occur on Umnak Island and possibly adjacent islands as long as the eruption continues.

The eruption at Okmok continues based on high levels of seismicity and ash continues to be erupted as indicated in satellite observations. Seismicity reached a peak at about 2200 Z (2:00 PM ADT) yesterday (July 12) and has been gradually declining since. Reports from Unalaska indicate no ash fall in Unalaska/Dutch Harbor since last night. However, as of 0300 PM ADT the NWS ash fall advisory for the Eastern Aleutian zone, including Nikolski and Unalaska/Dutch Harbor, remains in effect.

The eruption at Okmok continues based on high levels of seismicity and ash continues to be erupted as indicated in satellite observations. Seismicity reached a peak at about 2200 Z (2:00 PM ADT) yesterday and has been gradually declining since. Reports from Unalaska indicate no ash fall in Unalaska/Dutch Harbor since last night. However, as of 0730 ADT the ash fall advisory for Nikolski and Unalaska/Dutch Harbor remains in effect.

A strong explosive eruption began at approximately 1943 Z (11:43 AM ADT) and continues at this time based on high levels of seismicity recorded on the AVO seismic network. Seismicity reached a peak at about 2200 Z (2:00 PM ADT) and has been gradually declining since. The main mass of the ash cloud is at least 35,000 feet above sea level and is moving generally southeast from the volcano, with lesser amounts of ash moving eastward. Ash fall has been reported on eastern Umnak Island and in Unalaska/Dutch Harbor.

A strong explosive eruption began at approximately 1943 Z (11:43 AM ADT) and continues at this time based on high levels of seismicity recorded on the AVO seismic network. The ash cloud may be reaching in excess of 35,000 feet above sea level and is moving generally east and southeast from the volcano. Ash fall has been reported on eastern Umnak Island and in Dutch Harbor.

An explosive began at approximately 1943 Z (11:43 AM ADT) and continues. An ash cloud with a top 30,000-35,000 ft. above sea level is present.