Coats (1950) reports a minor explosive eruption at Mount Veniaminof in November, 1939.

Coats (1950) reports a mild ash eruption at Mount Veniaminof on March 28, 1944.
A March 15, 1944 Associated Press article states "The volcano of Veniaminoff has erupted again, passengers aboard a boat arriving from Chignik village reported today. The resultant fireworks lighted the surrounding country, said those who had witnessed the phenomenon."

From Yount and others (1985): "The more prominent of the two visible intracaldera cones of Mount Veniaminof went into eruption in early June 1983 and continued until early April 1984.
"* * * In this recent eruption, Perryville residents first saw puffs of ash on June 2, 1983. Early manifestations of the Strombolian eruption included a 90-m-wide sector graben and a circular depression (400 m in diameter and approximately 30 m deep) in the glacial-ice surface directly south of the active cone. By June 9, the 300-m-deep crater of the cone had filled to overflowing with juvenile bombs, blocks, and rising magma, resulting in a lava flow from a low point on the southwest side. The lava flow and subglacial heating caused rapid melting of the glacial ice on the south side of the active cone. By July 13, a vertical-walled, bilobate pit measuring approximately 1,300 m in the east-west direction, 400-800 m in the north-south direction, and 60-100 m deep had formed in the ice. The pit contained a lake of unknown depth and a southward-building lava delta. A subglacial tunnel in the ice-wall at the east end of the lake indicated drainage eastward along the caldera floor. Another tunnel, less clearly observed, may have drained from the northwest end of the lake toward a breach of the caldera wall at Cone Glacier.
"Ash emission was almost continuous during June and July 1983; occasional plumes were estimated to have been as high as 7,800 m. During this time, ash blanketed the intracaldera glacier and steam plumes occurred nearly continuously. The eruption appeared to wane from mid-August to early October, through this may be partly a function of paucity of reports and observations.
"Renewed activity was reported in early October. By this time the ice-pit lake had diminished to a small pond located between the wall of the ice pit and a new lava flow lobe. The October 1983-March 1984 eruptive phase was characterized by less ash emission and more lava flow activity than the June-August 1983 phase. A succession of flows from the southwest side of the cone resulted in a continual increase in volume and height of new lava in the ice pit, and the pit enlarged slightly in plan, losing its bilobate shape. Each flow lobe cooled rapidly due to the 1,800-m elevation and winter winds; snow was observed on lobes approximately a month old. Perryville residents observed incandescent lava fountaining up to an estimated 100 m above the cone on January 23, February 6 and 13, and March 2 and 3, 1984. Fountaining was intermittent, lasting one-half to one hour and was followed by quiescent periods of at least 45 minutes. Incandescent glow was last observed March 16, 1984. From mid-March to late April, activity was limited to continual emission of small steam plumes and rare ash bursts lasting up to two hours. An observation flight on April 11 revealed that all lava-flow lobes in the pit were dusted with snow."
The Smithsonian Institution Scientific Event Alert Network Bulletin, volume 5, number 1 reports that USGS personnel estimated that approximately 45x10^6 cubic meters of lava filled the ice pit between June, 1983 and January, 1984.

From Neal and others (1996): "Reports of activity at Veniaminof began in early 1993. Pilots reported a steam plume rising from the volcano on February 18, 1993. Confirmed magmatic activity was first sighted on July 30, 1993. Observers in Perryville reported black clouds rising over the summit beginning at 1430 ADT on July 30, 1993. A white steam cloud was present at other times. A small eruption plume was observed on satellite imagery by the NWS on July 30, but none were seen in the following days. On the morning of July 31, Perryville observers saw a gray cloud rising from the volcano and extending to the south. On August 2, commercial airline pilots observed intermittent venting of black ash clouds rising nearly 300 m (1,000 ft) above the active intracaldera cone. On August 3, U.S. Fish and Wildlife (USFWS) personnel reported a steaming pit in the snow at base of the west side of the intracaldera cinder cone. Pilot reports on August 3 described black ash and bombs erupting from the summit vent of the intracaldera cone at 30-60 second intervals to a height of 2,400 - 3,000 m (7,900-9,800 ft) above sea level (840 m [2,756 ft] above vent). A minor dusting of very fine ash occurred in Port Heiden after 2000 ADT on August 3, 1993. Residents of Perryville, Chignik, and Chignik Lake also heard a "rumbling noise" accompanied by a slight tremor at about 2200 that night. Flight restrictions around Veniaminof were put into effect August 4, 1993. On the morning of August 6, a resident of Port Heiden observed eruptions of ash and steam at 3-4 minute intervals; these plumes barely rose above the summit of the volcano. There were no reports of ashfall at other nearby villages. On August 12, a pilot reported ash venting 600-900 m (1,900 - 3,000 ft) above the crater with the ash cloud carried east-northeast.
"Poor weather precluded many observations during the fall. On October 1-2, residents of Port Heiden observed steam and ash emissions over Veniaminof. An Advanced Very High Resolution Radiometer (AVHRR) image from the late morning of October 2 -- the first clear satellite image in almost two months -- showed a faint northeast-directed plume and a thermal anomaly at the summit cinder cone. During the night of October 7, residents of Perryville observed bursts of incandescent material rising approximately 300 m (1,000 ft) above the summit. These bursts occurred about once every 10 minutes, were accompanied by loud rumbling sounds, and appeared to be similar in size to the eruptions in July and August. On October 14, residents of Perryville observed continued emission of a gray, steam and ash plume rising about 1 km (3,280 ft) above the summit. Though the summit was obscured by haze on October 22, observations from Perryville indicated a decrease in the level of activity relative to that earlier in the month.
"U.S. Coast Guard (USCG) pilots filmed eruptive activity and took photos of the intracaldera cinder cone on November 6, 1993. By then, a new pit (2.0 by 0.75 km [1.2 by 0.5 mi] wide) had formed in the ice adjacent to the cone on the east flank and contained an
active lava flow [See fig. 4 in original text]. Steam plumes rose from the outer margin of the lava where it came into contact with the ice walls of the pit. An ash-and-steam plume rose up to 2 km (6,560 ft) above the cinder cone, and a thin ash layer covered the ice-filled floor of the caldera.
"Activity continued intermittently for the remainder of 1993, (for post-1993 activity see Neal and others, 1995). During favorable wind and weather conditions, Port Heiden residents noted dark ash clouds above the volcano and deep rumbling was reported by residents in Port Heiden and Perryville."
From Neal and others (1995): "Reports of eruptive activity diminished in frequency with the onset of bad winter weather; however, reports of renewed, intermittent strombolian activity reached AVO in March 1994. On May 9, 1994, during the first AVO overflight, eruptive activity consisted of quiet lava effusion from the vicinity of the intracaldera cinder cone [see fig. 7 in original text]. This lava flow had melted an oval-shaped pit in the summit ice cap estimated to be about 1000 m (3,280 ft) by 800 m (2,625 ft) across and 30-50 m (100-160 ft) deep. Fractures in the ice surrounding the pit suggested subglacial melting. Unlike the 1983-84 eruption, no standing water was visible in the pit.
"On June 29, an especially vigorous eruption sent an ash cloud to a reported 4.8 - 5.5 km (16,000-18,000 ft) and the NWS issued a SIGMET (notice of SIGnificant METeorological events.) Additional reports of low ash bursts over the volcano or incandescent strombolian activity viewed at night were received through mid-August. Steam plumes, at times rising several hundred meters, were reported over the volcano until late September. Due to the remote nature of this volcano, the paucity of observations, and the frequently poor weather, we are uncertain of the history of declining eruptive activity in late 1994. However, on Advanced Very High Resolution Radiometer (AVHRR) satellite images unobscured by heavy cloud cover, thermal anomalies were detected in the area of the active intracaldera cinder cone of Mount Veniaminof into early 1995."
The Smithsonian Institution (Bulletin of Global Volcanism, volume 19, number 4) estimates the volume of the 1993-1994 lava field at 16-20 x 10^6 cubic meters.

From Neal and others (2005): "In mid-February, residents of Perryville, located 35 km (22 mi) south of Veniaminof, reported small ash clouds rising several hundred feet above the intracaldera cinder cone of the volcano. At other times, vigorous, ash-free steam plumes were reported. On February 19, AVO received a pilot report of a small black ash cloud rising approximately 300 ft (90 m) above the cone and fresh ash on the snowfield east of the cone [see fig. 13 in original text]. A satellite image from the same day showed a dark deposit within the Veniaminof summit caldera. Seismic activity coincident with these reports was insignificant and AVO considered these small explosions to be typical of background activity at Veniaminof where ground water within the active cone occasionally flashes to steam producing a small explosion. The volcano had last produced such activity over a several month-period in late 2002 and early 2003 (Neal and others, 2005; McGimsey and others, 2005). On February 23, AVO described this activity in a special Information Release but remained at Level of Concern Color Code GREEN. AVO received no reports of activity over the next two weeks. Satellite imagery did not indicate increased surface temperatures or further ash deposits and seismicity remained low. AVO ceased special mention of Veniaminof in its weekly updates on March 5.
"In mid-April, seismicity beneath Veniaminof began to increase and several episodes of volcanic tremor and isolated volcano-tectonic earthquakes were recorded. Tremor pulses were several minutes in duration and the largest were recorded on most stations in the network. On April 19, residents of Perryville reported a steam emission from the intracaldera cone that had occurred on April 18, possibly containing a small amount of ash. This burst rose an estimated 2,000 ft (610 m) above the intracaldera cone. Based on this renewed activity and elevated seismicity, AVO elevated the Level of Concern Color Code for Mount Veniaminof to YELLOW. NWS issued a VAA and the FAA issued a temporary flight restriction from the surface to 14,000 ft ASL (4,270 m) within a 10 nautical mile (18.5 km) radius of the center of the volcano.
"Over the next few weeks, Perryville residents reported vigorous steam plumes (often described as mushroom-shaped clouds) over the intracaldera cone. AVO received few reports of small ash emissions until April 25 when, using a newly installed remote video camera, as many as 25 small steam and ash emissions were observed over an 8-hour period, most rising about 2,000 ft (610 m) above the active cone [see fig. 14 in original text].
"Through the remainder of spring and into summer, passing pilots, Perryville residents, personnel at Wildman Lake Lodge, and the AVO internet camera continued to record occasional steam plumes and steam and ash bursts, at times reaching as much as 915 m (3,000 ft) above the intracaldera cone and drifting as far as 16-32 km (10-20 mi). Poor weather obscured views of the volcano on many days, however bursts of tremor recorded on the seismic network likely reflected the continuation of small ash emissions, or 'puffs'. On May 5, a pilot spotted ash to 610 m (2,000 ft) above the cone and drifting east-southeast; on May 18, a pilot reported ash up to 3,000 ft (915 m) above the cone and drifting 32 km (20 mi) downwind. On May 26, satellite images of the volcano showed ash deposits on the north and southeast caldera floor.
"Aerial views on June 27 revealed that much of the caldera floor was covered by a thin, dark layer of ash. On July 10, an AVO crew flying inside the caldera on a clear, calm day witnessed one of these ash bursts and captured it on video. As the helicopter approached the cone, only a faint wisp of steam and volcanic gas emerged from the summit of the intracaldera cone that consists of a series of coalescing craters each several 10s to 100 m wide. Suddenly, two closely spaced (20-30 seconds apart) vigorous explosions of gray-tan ash emerged from one of the central craters. The discrete puffs were followed by at least 2.5 minutes of continuous roiling of ash from the crater. Ash rose several hundred m (700-1,000 ft) above the cone and drifted downwind; ballistics and incandescence are not visible in this video clip. On July 22, an AVO field crew within the Veniaminof caldera witnessed another typical ash burst rising a few hundred ms (less than 1,000 ft) above the summit of the cone (fig. 15). Fallout was largely confined to the area around the base of the cone.
"AVO geologists visited the ice field by helicopter in late July and reported a discontinuous, 1- to 2-mm thick ash blanket. They observed no large bombs or ballistics beyond the base of the cone, suggesting that recent ash emissions had not been accompanied by energetic explosions of large rock fragments. Further, they reported no changes in the ice field that would indicate subglacial melting. Additional observations of the cone were made in early August and photographs capture ash-poor puffs rising from one of several summit craters on the cone [see figs. 16, 17 in original text]. On August 7, geologists recorded 6-10 puffs over the course of about 10 minutes of focused observation. They reached about 150 m (500 ft) above the summit of the cone in fairly calm wind conditions.
"Steam and ash emissions and correlative tremor bursts continued sporadically through the summer of 2004 but with decreasing frequency and intensity. Cloudy weather precluded any visual observations for much of September and October, however seismic signals continued to record small tremor bursts similar to those correlated with confirmed ash emissions earlier in the year. At times, only weak steaming was visible above the intracaldera cone. The last ash emission with localized ash fall was noted on the web camera images in early September. The pilot of a small aircraft reported 'light to moderate smoke' from Veniaminof on September 13. On October 26, AVO lowered the level of concern color code to GREEN based on a decline in the level of activity and an accompanying decrease in seismicity.
"In response to the 2004 unrest at Veniaminof, AVO staff conducted outreach to communities in the vicinity of the volcano and revised existing contact phone lists of observers and others in the area. To track and document activity, a web-camera system was installed in Perryville in April (with assistance from the Perryville School and Perryville Village Council, gratefully acknowledged.) These images along with other graphical and text information were made available to the public via the AVO web site. AVO issued seven special Information Releases on the activity at Veniaminof."

From McGimsey and others (2007): "After almost 4 quiet months, on January 4, 2005, AVO received a pilot report of small bursts of ash from the active cone rising a few hundred meters and drifting east, producing a narrow spoke-like deposit on snow within the caldera (see figs. 31 and 32 in original text). This activity seemingly correlated with a period of continuous tremor recorded on the local seismic network that day, and a weak thermal anomaly was detected in an AVHRR satellite image. AVO upgraded the Level of Concern Color Code for Veniaminof from Green to Yellow. AVO seismologists noticed that weak seismic tremor had begun on January 1 and increased over the subsequent week to levels last observed in May-June 2004. Steam and ash emissions continued from the next several days and residents of Perryville, located 35 km (22 mi) south of Veniaminof, reported incandescence; the caretaker a ta local hunting lodge located west-southwest of the volcano reported seeing intermittent bursts of steam and ash. Beginning on January 8, a persistent thermal anomaly began appearing in satellite images. Then, on January 10, following nearly 48 hours of minor but nearly continuous ash emissions - some bursts reaching to 13,000 ft (3,692 m) above sea level - AVO raised the Level of Concern from Yellow to Orange. The maximum amplitude of the seismicity had by then slightly exceeded that observed during the previous phase of unrest, which ended in September 2004. AVO launched an overflight on January 11. The crew observed nearly continuous low-level ash and steam emission from the central cone and much of the caldera was thinly covered in ash (see fig. 33 in original text).
"Seismic data, web camera views, and satellite images indicated that low-level ash emissions continued for the next 5 weeks. The seismicity was characterized by low-amplitude tremor with occasional larger bursts. Weather permitting, satellite views showed anomalous heat at the summit cone consistent with hot blocks and ash ejection from the vent. The web camera showed intermittent ash clouds with the highest reaching almost to 13,000 ft (4,000 m) ASL. Strombolian eruptive activity was visible to the residents of Perryville during the night of February 3. Then during the week of February 25, seismicity decreased substantially and only minor emissions of steam were observed. AVO reduced the Level of Concern from Orange to Yellow. By the end of the following week, volcanic tremor had subsided and seismic activity was deemed to be at background levels and the Level of Concern was reduced from Yellow to Green (see table 6 in original text).
Excerpts from AVO's information releases during this Veniaminof eruption are available online at: www.avo.alaska.edu/archives/ve…
The Smithsonian Institution's Global Volcanism Bulletin (v. 30, n. 2) summarizes the event as follows: "AVO raised the Concern Color Code at Veniaminof from Green to Yellow on 4 January because around that time several small ash emissions from the volcano's intracaldera cone were observed on the web camera in Perryville. Ash emissions were visible starting around 0938, but may have been obscured by meteorological clouds in previous images. The discrete ash emissions were small, rose hundreds of meters above the cone, and dissipated as they drifted E. Minor ash fall was probably confined to the summit caldera. Very weak seismic tremor was recorded beginning on 1 January, and increased slightly over the next 2 days. These seismic signals were similar to those recorded during steam-and-ash emissions in April to October 2004. However, there were no indications from seismic data that events significantly larger than those observed around 4 January were imminent.
"AVO raised the Concern Color Code at Veniaminof from Yellow to Orange on 10 January as ash emissions from the volcano's intracaldera cone reached heights of nearly 4 km during 8-10 January [see figure 11 in original online source]. Seismicity remained at elevated levels and satellite images showed a persistent thermal anomaly at the intracaldera cone. On 11 January, the Anchorage VAAC again reported emission of a thin ash cloud to ~ 3 km altitude visible on the Perryville web camera. On 12 January the Anchorage VAAC reported emission of a thin ash cloud, visible on the Perryville web camera, that rose to 3-4 km altitude, extended ENE, and dissipated within ~ 55 km of the volcano. On 14 January, a satellite image showed a thermal anomaly in the vicinity of the Veniaminof summit. Although the anomaly appeared less intense than when first detected on 8 January and volcanism seemed to have declined significantly since 12 January, activity still remained significantly higher than normal with occasional bursts of volcanic tremor.
"During the rest of the month of January, seismic data, web camera views, and satellite images indicated that low-level ash emissions continued at Veniaminof. Seismicity was similar to levels observed during the previous week, consisting of low-amplitude volcanic tremor with occasional larger bursts. During clear weather, satellite imagery showed anomalous heat at the summit cone, consistent with hot blocks and ash being ejected from the active vent. In addition, the web camera showed intermittent ash plumes reaching as high as 3 km altitude. Occasional stronger bursts of seismic tremor during 20-21 January and around 28 January may have indicated plumes to higher levels, but not above 4 km altitude. Veniaminof remained at Concern Color Code Orange.
"Activity during February 2005. On the evening of 3 February, Strombolian activity at Veniaminof was visible by residents of Perryville ~ 30 km from the volcano. Activity was also observed on web camera views and seen by satellite as an increase in radiated surface heat. An increase in seismicity suggested that Strombolian activity may have continued through 4 February while the volcano was obscured by clouds.
"During 28 January to 4 February, seismicity at Veniaminof was similar to levels for the previous week, with low-amplitude tremor and occasional larger bursts. During clear weather, satellite imagery showed anomalous heat at the summit cone, consistent with hot blocks and ash being ejected from the active vent. The web camera showed intermittent ash plumes reaching as high as 3 km altitude. Veniaminof remained at Concern Color Code Orange.
"Low-level Strombolian eruptive activity continued at Veniaminof during 4-11 February. On 9 February, an ash burst rose hundreds of meters above the intracaldera cone. Satellite images continued to show a thermal anomaly in the vicinity of the intracaldera cone, consistent with the presence of hot material at the vent. Seismicity remained above background levels at the volcano. On the morning of 10 February there was a distinct increase in the amplitude and frequency of earthquakes. The increase continued through 11 February. This activity was consistent with more energetic explosions from the active cone, but there were no indications that the bursts rose higher than 4 km altitude. Veniaminof remained at Concern Color Code Orange.
"During 11-18 February, it was likely that low-level Strombolian eruptive activity continued at Veniaminof based on seismic data and satellite imagery. Cloudy conditions obscured web camera views of the volcano, and no ash emissions were observed above the cloud cover. Seismicity remained above background levels at Veniaminof. The character of the seismicity changed slightly during the report period, with frequent periods of continuous banded volcanic tremor occurring, but the amplitudes of earthquakes did not increase. This activity was consistent with explosions from the active cone; however, there was no indication that these bursts rose more than 4 km altitude. Veniaminof remained at Concern Color Code Orange.
"Seismicity decreased substantially at Veniaminof during 18-25 February in comparison to previous weeks, leading AVO to decrease the Concern Color Code from Orange to Yellow. Periods of volcanic tremor diminished, and no discrete events associated with ash bursts had occurred for several days. Only minor steam emissions were seen. AVO received no reports of ash emissions from pilots or ground observers. AVO concluded that given the decline in seismicity, it appeared that the most recent episode of Strombolian eruptive activity at Veniaminof had ended.
"Activity during March 2005. A further reduction in activity at Veniaminof during 25 February to 4 March led AVO to reduce the Concern Color Code from Yellow to Green, the lowest level. For more than a week seismic activity was at background levels, periods of volcanic tremor had ceased, and there were no discrete events associated with ash bursts. Only minor emissions of steam were observed on the web camera and satellite imagery. AVO received no reports of ash emissions from pilots or observers on the ground. They concluded that given the decline in seismicity it appeared that the most recent episode of eruptive activity had ended at Veniaminof."

From McGimsey and others (2007): "Veniaminof remained relatively quiet [since February, 2005] until early September when several minor bursts of ash were observed by Perryville residents and visible on the web camera (see fig. 34 in original text). This and an increase in seismicity prompted AVO to elevate the Level of Concern from Green to Yellow on September 7. The minor unrest continued only for a couple of weeks when seismicity once again decreased to background level and there were no observations of emissions. AVO reduced the Level of Concern from Yellow to Green on September 28.
"Then, on November 4, a low-level, minor ash emission visible in the webcam prompted AVO to raise the Level of Concern from Green to Yellow. Slightly elevated seismicity persisted for the next few weeks but poor weather conditions precluded visual observations. By mid-December, seismic levels were again down to background level, and on December 30, the Level of Concern was downgraded from Yellow to Green, the 8th Color Code change of the year for Veniaminof (see table 6 in original text)."
From the Smithsonian Institution (2006, v. 31, n. 3): "On 7 September 2005, the Alaska Volcano Observatory (AVO) noted several minor bursts of ash from the volcano during the afternoon. Ash bursts continued to occur through at least 9 September, with ash rising less than 3 km altitude, and with the ash confined to the caldera. Over the following 2 weeks, minor ash emission continued at a rate of 1-5 events per day based on interpretations of seismic data. AVO reported that it was likely that diffuse ash plumes rose to heights less than ~ 3 km and were confined to the summit caldera. Cloudy weather during 16-23 September prohibited web-camera and satellite observations of Veniaminof, but seismic data indicated diminishing activity. On 28 September seismicity had remained at background levels for over a week, and there was no evidence to suggest that minor ash explosions were continuing.
"On 4 November 2005, a low-level minor ash emission occurred from the intracaldera cone beginning at 0929. Ash rose a few hundred meters above the cone, drifted E, and dissipated rapidly. Minor ashfall was probably confined to the summit caldera. During the previous 2 weeks, occasional steaming from the intracaldera cone was observed. Very weak seismic tremor and a few small discrete seismic events were recorded at the station closest to the active cone. However, AVO reported that there were no indications from seismic data that a significantly larger eruption was imminent."
Execerpts from AVO's weekly updates and information releases for this time period can be found at this website: www.avo.alaska.edu/archives/Ve….

From the Smithsonian Institution (2006, v. 31, n. 3): "On the morning of 3 March 2006 ash again rose a few hundred meters above the intracaldera cone, drifted E, and dissipated rapidly. Ashfall was expected to be minor and confined to the summit caldera. Seismicity was again low and did not indicate that a significantly larger eruption was imminent. Over the week of 5-10 March, seismicity was low but slightly above background.
"On the morning of 10 March, AVO received a report from a pilot of low-level ash emission from the intracaldera cone. Clear web-camera views on 9 March showed small diffuse plumes of ash extending a short distance from the intracaldera cone. The Anchorage Volcanic Ash Advisory Center (VAAC) reported a steam/ash plume noted on web-cam and satellite on 13 March 2006 at 0500Z (12 March 2006 at 2000 hours local), moving NNW at 9.2 km/hr and falling to the land surface. Web-cam images on 22 March showed a very diffuse steam-and-ash plume that was confined to the summit caldera, and on 24 March showed a steam-and-ash plume drifting from the summit cone at a height of less than 2.3 km. This level of activity was similar to that on 23 March, but higher than activity on 21 and 22 March, when a very diffuse steam-and-ash plume was confined to the summit caldera.
"The flow of seismic data from Veniaminof stopped on the evening of 21 March 2006, and the problem was expected to continue until AVO staff could visit the site to repair the problem. Absent seismic data, the volcano could potentially still be monitored in other ways such as using web-camera and satellite images. Imagery was obscured by cloudy weather after 21 March. On 26 March 2006, a pilot reported a small ash plume rising above the volcano. Low-altitude ash emissions from Veniaminof were visible during 31 March to 7 April. On 6 April, a pilot reported an ash plume at a height of 3 km. AVO stated in its weekly report of 14 April 2006 that the seismicity at Veniaminof remained low but above background. Internet camera and satellite views had been obscured by cloudy weather, and AVO lacked new information about ash clouds or activity."
Continued activity was summarized by the Smithsonian Institution (2006, v. 31, n. 8): "Intermittent, very small-volume steam and ash bursts from the intra-caldera cone have been typical of this volcano intermittently over the past few years, and this pattern continued. The previous report mentions several minor bursts of ash, particularly on 13 June 2006 and 7 September, and minor white plumes through mid-September. This report discusses the interval 8 April through 15 September. Seismicity during this interval was nearly always low, although it often rose above background.
"Clouds obstructed visibility during 7-14 April. For the duration of April and June, activity remained low with few steam plumes containing minor amounts of ash. On 30 May a weak daytime thermal anomaly was recorded, possibly due to solar heating inside the dark intra-caldera cone. Intermittent clear weather on the week ending 9 June indicated weak steam plumes.
"On 13 June an ash emission rose to a height estimated at ~ 600 m above the summit area, as reported by a passing aircraft. Transient plumes were seen on satellite imagery during the week ending 21 July.
"During the week ending 28 July, an AVO field party flew over the summit and observed typical steaming from the intra-caldera cone with no signs of recent ash emissions. Satellite and web camera views during occasional clear periods showed no other signs of activity. Occasional satellite views during clear weather failed to disclose new ash emissions during 28 July through 15 September.
"AVO noted a slight increase in seismicity starting 2 August but in the subsequent weeks it again returned to low levels. Available satellite and camera views continued to reveal occasional small white plumes through 15 September."
Steam plumes without ash emission continue to be observed at Veniaminof, as of this writing (March 21, 2007).

McGimsey and others (2011) report that by January 2007, the intracaldera cinder and spatter cone was producing only minor, diffuse steam plumes that rose at most a few hundred meters above the vent. * * * Foloowing several weeks of cloudy weather, clear web camera views on the morning of February 16, 2007, revealed vigorous steaming from the intracaldera cone [see fig. 22 in original text]. Clouds and a short camera outage prevented observations for several days, and then on the morning of February 20, a clear view showed little to no steaming from the cone. Minor steaming was visible through February 24 when weather permitted, and by February 25, no signs of steam emissions were apparent in web camera images. Over the next couple of months, intermittent clear views of the volcano in either web camera images or in satellite images showed that occasionally minor steam plumes were issuing from the intracaldera cone. Seismicity had decreased to background levels several months prior, and the last ash-laden plume visible in web camera images was on November 2, 2006. The last thermal anomaly visible in satellite images was on July 5, 2006. Ground observers and pilots reported no unsual activity in recent months, and therefore on April 26, 2007, AVO lowered the Aviation Color Code/Volcano Alert Level to GREEN/NORMAL. Based on historic patterns of eruptive behavior, AVO anticipated continued steaming from the cone. Indeed, Veniaminof continued to steam intermittently throughout 2007."

For additional photographs and observations of this event, please see: Neal, C.A., McGimsey, R.G., Dixon, J.P., Manevich, Alexander, and Rybin, Alexander, 2009, 2006 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2008-5214, 102 p., available at pubs.usgs.gov/sir/2008/5214/.

From AVO's Volcanic Activity Notice on February 22, 2008: "On February 22, 2008, several minor bursts of ash from Veniaminof were observed on AVO webcam images and recorded in seismic data this morning. The bursts rose less than 9000 ft ASL (only a few hundred feet above the active intracaldera cinder cone), and were confined to the caldera." Since February 22, AVO has continued to note elevated seismicity at Veniaminof and to view steam and occassional ash in Veniaminof webcam images.

From Neal and others (2011): Intermittent low-level activity at Veniaminof continued in 2008 with minor phreatic ash emissions and periods of slightly elevated seismicity. Beginning in mid-February, seismicity (in the form of 1-2 minute tremor bursts with occasional harmonic banding) became slightly more energetic and AVO staff noted vapor plumes in web camera images from Perryville, 35 km (22 mi) south of the volcano.
"A weak ash emission event was captured on the AVO web camera on February 22, noted during routine analysis by AVO and reported via email by a watchful citizen, prompting AVO to issue a YELLOW/ADVISORY. Minor eruptions of ash occurred about once every 20-30 minutes over several hours, producing small plumes that rose at most about 300 m (1,000 ft) above the intracaldera cinder and spatter cone [fig. 8; imageid 14025]. Some of these small bursts could be correlated with a clear multi-station seismic event [see fig. 9 in original text]. Ash clouds dissipated rapidly and did not extend beyond the caldera rim; in between bursts, a white water vapor plume was common. These were similar to those seen during 2005 (McGimsey and others, 2007).
"On February 23, only a white vapor plume rose above the cone. Tremor bursts continued, increasing in intensity (both number of discrete volcano-tectonic earthquakes (VTs) and longer tremor episodes) on February 29. In response, AVO initiated additional checks of seismic data for the volcano and implemented a Real Time Seismic Amplitude (RSAM) alarm for Veniaminof (Murray and Endo, 1992). A pilot reported ash to 10,000 ft (3,050 m) on February 29 and the NWS issued a SIGMET. Perryville residents using a telescope reported seeing large blocks, orange in color, thrown out of the plume during daylight hours on February 28. The lack of a thermal anomaly or night time reports of incandescence suggests these ballistic objects probably were altered and oxidized lava bombs rather than fresh, hot (and thus, 'glowing') magmatic ejecta.
"In addition to more frequent analysis of seismicity, AVO initiated automatic ash dispersal runs using the PUFF model (Searcy and others, 1998) for hypothetical Veniaminof eruptions.
"Seismicity and emissions decreased in early March and AVO discontinued the heightened seismic watch. A March 4 ASTER image showed a small vapor plume emanating from the intracaldera cone but no anomalous temperatures indicative of significant activity (R.L. Wessels, USGS, written commun., 2008).
"On May 3, after several months of no further ash emission events, AVO downgraded Veniaminof to GREEN/NORMAL, where it remained for the rest of 2008 and into 2009."

From McGimsey and others (2014): "On January 8, 2009, a pilot reported seeing a wispy, light-gray plume between 6,500 and 10,500 ft (1,980 and 3,200 m), and extending 28 km (15 mi) downwind from the volcano. A passenger in an aircraft took a photograph of the plume. The AVO/USGS web camera located at nearby Perryville also captured the plume that day.
"AVO remote sensing experts interpreted the 'gray tone' attributed to the plume to be backscatter shadow from the plume rather than ash content. Similar steaming was recorded in web camera images most of the previous week and again during the week of March 17. The web camera became inoperative on March 17 due to relocation of the village office hosting the camera. The camera would not come back online until May 27, 2009.
"In response to an increase in seismic activity across the entire network, AVO issued a VAN on May 7, 2009, elevating the Aviation Color Code/Volcanic Alert Level to YELLOW/ADVISORY. Because the web camera was inoperative, calls to local observers on May 9 produced reports of a 'steady stream of light steam, with occasional small puffs.' Low-level tremor was recorded the week of May 18, but the activity soon diminished, and with no further visual reports of activity, on May 26, 2009, AVO issued a VAN downgrading the volcano to GREEN/NORMAL. A few days later, on May 29, tremor returned and abruptly increased later in the day. The web camera was once again operating, but the view on this day was obscured by clouds. Nothing unusual was noted in satellite images. Tremor continued through May 30, 2009, but at a lower amplitude than previously recorded, and then diminished entirely. Thus, no change in status was forthcoming.
"On June 23-24, 2009, a small swarm of low-frequency earthquakes was recorded at Veniaminof, the last of the calendar year as the network began deteriorating. On the morning of October 19, 2009, a U.S. Coast Guard flight crew flying over Bristol Bay reported 'steady smoke and ash' coming from the center of Veniaminof. Web camera images at the time showed a voluminous, low-level steam plume over the volcano, but no indication of ash.
"On November 17, 2009, due to continued station outage, reducing the network to only a single station, AVO issued a VAN downgrading the volcano from Aviation Color Code/Volcano Alert Level GREEN/NORMAL to UNASSIGNED, and delisting it from the inventory of seismically monitored Alaska volcanoes. The volcano would remain at this status through the remainder of 2009."

From Dixon and others (2015): "Mount Veniaminof Volcano is a frequently active volcano on the Alaska Peninsula. From 2002 through 2010, nearly continuous low-level eruptive activity waxed and waned, producing wispy plumes that were reported by pilots, recorded on satellite images, and observed in images from the Federal Aviation Administration (FAA) Web camera in Perryville, 35 km (22 mi) east of the volcano. Activity ceased during the first one-half of 2013. In early June 2013, a several-day period of abrupt and gradually increasing levels of seismic tremor heralded the onset of a largely effusive eruption from the intracaldera cinder cone (table 6 in original text). Over the next 5 months, ash emissions and Strombolian explosions accompanied by five lava flows poured down the flanks of the active cone and advanced onto the surrounding ice-filled caldera. This eruption constructed a new spatter cone within the summit crater of the main active cone (Waythomas, 2013).
"On June 7, 2013, gradually increasing, low-frequency tremor was recorded on two seismograph stations (VNWF and VNHG) as satellite images recorded elevated surface temperatures at the summit of the intracaldera cinder cone (fig. 10 in original text). The following day, June 8, in response to the continuing increase in seismic tremor, AVO upgraded the Aviation Color Code and Volcano Alert Level from GREEN/NORMAL to YELLOW/ADVISORY. Over the next several days, seismic tremor steadily increased. On June 13, seismicity levels and elevated surface temperatures at the summit of the cinder cone, as observed in satellite images indicated an eruption was likely underway. AVO issued a Volcanic Activity Notice (VAN) upgrading the Aviation Color Code and Volcano Alert Level from YELLOW/ADVISORY to ORANGE/WATCH. On June 14, ash deposits on the ice/snow-covered caldera floor were visible in satellite images, and the presence of lava on the cone was observed.
"Clear weather provided good views from the FAA Web camera, located in nearby Perryville, as the eruptive activity increased and produced minor ash clouds (fig. 11 in original text). Satellite views on June 18 confirmed the Strombolian eruption and effusion of a 100 m (330 ft) wide lava flow (Flow 1; flow numbers refer to those identified in figure 12 [in original text] down the southwestern flank of the main cinder cone). Interaction of the lava with the caldera snow and ice field at the base of the main cone generated water-rich, ashy plumes (fig. 13 in original text). Clear satellite views the following day showed active flow lobes advancing over the ice at the base of the cone (fig. 14 in original text).
"For the next couple of weeks, the activity continued with the southern flank flows (Flows 1 and 2) advancing and widening, with minor accumulations of ash on the caldera floor (figs. 15 and 25 in original text); Flow 2 descended east and adjacent to Flow 1, and Flow 3 advanced between and over the margins of Flows 1 and 2. The Strombolian eruption was visible in infrared satellite imagery, from the FAA Web camera in Perryville, and from several local lodges and remote camps (figs. 16 and 17 in original text).
"On July 16, AVO geologist Chris Waythomas visited the caldera by helicopter, making observations and taking the first close-up photographs documenting the lava flows and ice cauldron formation (figs. 18 and 19 in original text). These close-up images of the vent area showed a new cone of accumulated spatter nested within the summit crater of the main cone.
"By late July, the activity appeared to be waning as seismicity decreased, and reached a low level by August 2. In clear satellite views over this period, elevated surface temperatures were consistent with the still cooling, but no longer advancing, lava flow. On August 11, seismic tremor increased abruptly, and very high surface temperatures were observed in satellite images, suggesting that eruptive activity had resumed and lava again was flowing from the summit vent. Nighttime satellite images on August 12 confirmed lava erupting from the cone, and a clear morning view from the Perryville Web camera showed a minor ash column and cloud over the summit cone.
"On August 18, AVO geologist Game McGimsey accompanied Ben Edwards, Dickinson University, on a National Geographic Society-sponsored visit to the caldera to document the ongoing activity, particularly the interaction of lava flows and the surrounding ice field. The southern flank lava flows had coalesced and largely melted into the ice, enlarging the ice cauldrons documented in July by Chris Waythomas, USGS/AVO (fig. 20 in original text). Steam rose from the margins where the hottest parts of the flows were still in contact with ice and water.
"Strombolian explosions of incandescent lava and minor ash emissions were observed at the central active vent on August 18 (fig. 21 in original text). Two new lava flows issued either from tubes emerging from accumulations of spatter near the vent rim on the northeastern flank of the new cone, or from vents through the base of that cone. The flows descended to the ice field below, coalescing and forming another ice cauldron (fig. 22 in original text); forming Flow 4 (Waythomas, 2013). Voluminous steam generated by interactions of lava and ice/water obscured views into the cauldron. Forward Looking Infrared Radiometer (FLIR) images delineated the lava flows and hot spatter on the cone (fig. 22 in original text). As measured by the FLIR, maximum temperatures reached 700 to 800 degrees C.
"Elongated lobes of sediment extended from the southern side of the ice cauldron, forerunners to the fifth and final lava flow of the eruption (figs. 23 and 24 in original text). Eruptive activity continued unabated for the next 12 days, and on August 30, AVO issued a VAN to report the intense seismicity, lava fountaining, and ash emissions as high as 15,000-20,000 ft (4,570-6,100 m) ASL. This marked the strongest unrest and eruptive activity since the eruption began in June. Satellite images on September 6 indicated further development of the lava flows on the northeastern flank (Flow 4), expansion of the main ice cauldron at its base, and creation of a second ice cauldron. A new lobe of the lava flow (Flow 5) also appeared in the satellite images, advancing southward from the main cauldron of Flow 4. The flow was captured in aerial photographs the following day (fig. 24 in original text). This flow continued to advance for possibly another week, but, by September 19, no evidence of active lava flows was observed in satellite images. Seismicity had begun to decrease during the week and the eruption appeared to be waning.
"In response to the decrease in seismicity, and no evidence of eruptive activity in satellite and Web camera images, AVO issued a VAN on September 20 to downgrade the Aviation Color Code and Volcano Alert Level from ORANGE/WATCH to YELLOW/ADVISORY. An October 1 aerial image shows all five lava flows, partially snow covered, and only minor steam emissions from the summit vent (fig. 13 in original text).
"On October 6, an abrupt increase in seismic tremor and the observation of highly elevated surface temperature indicated a resumption of lava effusion, and AVO responded by upgrading the Aviation Color Code and Volcano Alert Level to ORANGE/WARNING. No ash emissions were observed, and within a few days, seismicity began decreasing in what would be a downward trend coincident with the final end of eruptive activity in 2013. The Aviation Color Code and Volcano Alert Level were downgraded on October 17 to YELLOW/ADVISORY. Throughout the remainder of 2013, occasional elevated surface temperatures were observed in satellite images consistent with the cooling lava flows, and steam emission from the summit vent was visible on clear days in Web camera images.
"The 2013 eruption of Veniaminof produced about 5 x 105 m3 of erupted lava, comparable in size to the 1983 eruption (Waythomas, 2013). A real-time seismic amplitude (RSAM) time series (Endo and Murray, 1991) from seismic station VNWF (fig. 11 in original text) is shown in figure 25 for the 5-month-long eruption, including significant eruptive events and color code changes (Waythomas, 2013). Before- and after-eruption views of the intracaldera cinder cone and geomorphic changes produced by the 2013 eruption are shown in figures 26 and 27 [in original text]."
From Cameron and others, 2017: "The volcano gradually returned to a state of rest, and by early July 2014, seismicity had returned to normal background levels. AVO downgraded the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL on July 9, 2014. Minor steam emissions and cooling of the lava flows continued intermittently for the remainder of the year. Several episodes of low-frequency events and tremor bursts occurred over the last one-half of the year (for example, July 15, October 8, December 18) as reported by AVO seismologists; however, these events were not associated with eruptive activity and are interpreted as continued degassing of the magmatic system."

From Dixon and others, 2017: "Mount Veniaminof had a 2-month-long period of increased seismic unrest in 2015. At the end of September, seismicity at Mount Veniaminof increased in the form of volcanic tremor and small low-frequency earthquakes. This type of activity was a known precursor to previous eruptions, most recently in 2009 (McGimsey and others, 2014) and 2013 (Dixon and others, 2015). On October 1, after the activity persisted for 1 day, the Aviation Color Code and Volcano Alert Level were raised to YELLOW/ADVISORY. Throughout October and early November, clear views from the Federal Aviation Administration (FAA) Perryville northwest web camera occasionally showed minor steam plumes issuing from the intracaldera cone (fig. 11[original text]). The intermittent, short bursts of seismic tremor persisted into November, indicating continued unrest. At the end of November, the seismic unrest at Veniaminof decreased to near background levels. On December 11, the Aviation Color Code and Volcano Alert Level was lowered to GREEN/NORMAL."

From Cameron and others, 2023: "The 2018 eruption of Mount Veniaminof took place from early September to late December, ending a roughly 5-year repose since the end of its previous eruption in October 2013 (Dixon and others, 2015). Eruptive activity took place from a ~300-meter-high cone within the summit-defining, ice-filled caldera of Mount Veniaminof. All known historical eruptions have taken place at this cone, although only 5 of the 18 documented historical events produced lava flows.
"Seismic unrest at Mount Veniaminof began late on September 2, 2018. AVO responded on September 3 by raising the Aviation Color Code and Volcano Alert Level from GREEN and NORMAL to YELLOW and ADVISORY, and on September 4 raised them again to ORANGE and WATCH. Lava fountaining, which likely began as early as September 6, was underway by September 7. By September 14, a lava flow extended about 800 m [2600 ft] down the south flank of the summit cone. This flow eventually covered about 600,000 square meters (m2) [6.5 million square feet (ft2) or 0.23 square miles (mi2)], and intermittent ash emissions reached an altitude of 20,000 ft (6,000 m) ASL. Trace ashfall dusted nearby Perryville, Alaska, 35 km [22 mi] south of the volcano.
"More details of the 2018 eruption are published in Loewen and others (2022) and Waythomas and others (2022). Information about the 2018 eruption is derived from geophysical instrumentation on or near the volcano, including an 8-station seismic network, regional infrasound sensors, frequent satellite images of the eruption, occasional aerial photographs taken by passing pilots, and webcam images of the volcano from Perryville. Overall, eruptive activity consisted of occasional explosive emissions of ash and steam, episodes of lava fountaining, and the effusion of lava flows. Nearly continuous seismic tremor began at Mount Veniaminof late on September 2, and in response, AVO raised the Aviation Color Code from GREEN to YELLOW and the Volcano Alert Level from NORMAL to ADVISORY the next day. By the early afternoon of September 4, minor ash emissions were apparent in webcam images and were seen by observers in Perryville. This prompted AVO to raise the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH.
"Satellite imagery showed a trace amount of ashfall over the southwest sector of the caldera icefield. Webcam images obtained throughout the days of September 4-5 showed distinct, pulsatory ash emissions consistent with small Strombolian explosions. Diffuse ash emissions that reached an altitude of about 10,000-15,000 ft (3,000-4,600 m) ASL were observed by passing pilots on September 5. On September 7, incandescence was observed in early morning webcam images from Perryville, and mid-infrared satellite images showed strongly elevated surface temperatures at the intracaldera cone. These observations indicated that lava fountaining was underway by September 7, though initial lava effusion may have begun as early as September 6. Seismicity at the time was characterized by long-period events and pulsatory tremor bursts, the latter of which lasted as long as a few minutes, though it also included intermittent harmonic tremor (primarily on September 3). The tremor became more continuous around September 7.
"On September 11, a passing pilot observed and photographed several thin, ribbon-like lava flows, fed by low fountaining or spattering, on the south flank of Mount Veniaminof’s intracaldera cone and coalescing at the cone’s base. A WorldView-3 satellite image acquired on the same day showed lava erupting from as many as four small vents in the same area and feeding a lava flow covering about 50,600 m2 [545,000 ft2]. On September 16 and 18, Sentinel-2 satellite images showed definitive steam emissions associated with lava-ice interaction at the terminus of the lava flow, and on September 25, robust, vertically rising steam emissions associated with lava-ice interaction were evident in Perryville webcam images. Aerial photographs taken on September 26 confirmed that the lava flow had begun melting into the ice and snow on the south side of the intracaldera cone. Conspicuous concentric subsidence cracks grew around the periphery of the lava flow as the glacier responded to this melt-induced loss of mass.
"Sulfur dioxide emissions were detected near Mount Veniaminof on September 20, 24, and 25 by multiple satellite sensors. The volcano emitted about 500 metric tons (t) [~550 U.S. tons] of SO2 on September 25, whereas emissions detected on September 20 and 24 were barely above background levels. Regional seismic networks detected ground-coupled airwaves on September 25–27, indicating Strombolian explosions were taking place. On September 27, an infrasound array in Dillingham, Alaska (322 km [200 mi] north of the volcano), also recorded explosive signals from the volcano.
"Lava effusion characterized activity in early October and was associated with continuous tremor, nighttime incandescence, and persistent, strong thermal signals at the intracaldera cone. Measurements from the Ozone Monitoring Instruments (OMI) and the Infrared Atmospheric Sounding Interferometer (OMPS) detected sulfur dioxide emissions on October 4 and 10, but at amounts just above background levels (fig. 5). The total surface area of new lava flows by October 3, as determined from satellite data, was 184,000 m2 [about 2 million ft2].
"Visibility improved considerably on October 18 compared to the previous several weeks, allowing a webcam in Perryville to record a billowy, low-altitude ash cloud extending southeast from the intracaldera cone. Several satellites detected SO2 on October 17 and 18, with OMI measuring about 270 t [300 U.S. tons] of SO2 emitted near Mount Veniaminof on October 18. Ash emissions reached an altitude of about 20,000 ft (6,000 m) ASL on October 19, and on October 23, satellite imagery showed minor ash deposits in the summit crater. Trace ashfall was reported in Perryville on October 25. Satellite observations that day indicated that lava had covered a total area of about 385,000 m2 [about 0.15 sqaure miles (mi2)]. The volcano remained restless through the end of October, with continued lava effusion and intermittent minor ash emissions. Sulfur dioxide was again detected in satellite data on October 30 and 31, but in amounts just slightly above background levels.
"By about November 3, activity at Mount Veniaminof began transitioning to episodic emissions of more robust steam and ash clouds, which appeared in satellite and webcam data. Satellite imagery from the early morning of November 5 showed an eastdrifting ash cloud, confirmed by a pilot’s observation, extending at least 60 km [37 mi] beyond the vent and reaching a maximum altitude of about 14,000 ft (4,300 m) ASL. From November 6 to 19, satellite data and occasional webcam images showed a persistent volcanic cloud of steam and ash extending as far as about 64 km [40 mi] from the intracaldera cone at an altitude that varied from 8,000 to 12,000 ft (2,400 to 3,700 m) ASL. Satellite instruments also detected SO2 near the volcano throughout early to mid-November, though the seasonal decline in ultraviolet light made the detection and accurate estimation of atmospheric SO2 loading less certain.
"On November 19, volcanic tremor increased in amplitude to reach the highest levels that had been measured up to that point in the eruption. This increase in seismicity was accompanied by infrasound detections on an array in Dillingham, which continued for the next few days. Satellite data from November 19 indicated that lava and tephra from the eruption now covered 540,000 m2 [0.2 mi2].
"Conditions at the volcano escalated again on November 21, with increasing ash emissions and tremor amplitudes. An ash cloud detected in satellite imagery now extended more than 240 km [150 mi] southeast from the vent, reaching an altitude of at least 15,000 ft (4,600 m) ASL. This cloud was also observed from Perryville, where residents reported distinct "booming" sounds - likely explosions - coming from the direction of the volcano. The level of seismicity and the extent of the ash cloud prompted AVO to raise the Aviation Color Code and Volcano Alert Level to RED and WARNING.
"Mount Veniaminof emitted ash nearly continuously for much of November 21 as the ash cloud continued lengthening to the southeast, eventually reaching a distance of at least 400 km [250 mi] from the vent. Trace ashfall was again reported at Perryville on November 21 and 22. Activity began to decline by the late afternoon of November 21 (AKST), and on November 22, AVO lowered the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. Clear webcam views from Perryville on November 22 showed nearly continuous ash emissions extending as far as 100 km [62 mi] beyond the vent and reaching an altitude of about 10,000 ft (3,000 m) ASL. Unobstructed nighttime views showed incandescence at the summit.
"Coincident with a gradual decline in tremor amplitude, by November 25, ash emissions were no longer evident from the intracaldera cone. On November 27, however, the RSAM of volcanic tremor increased slightly, and AVO detected occasional infrasound pulses on arrays in the Alaskan cities of Dillingham, Sand Point, and Akutan. This slight increase in activity was associated with the appearance of minor ash emissions in satellite data. From November 30 to December 3, data transmission from the Mount Veniaminof remote seismic stations was interrupted, so AVO relied primarily on satellite observations and regional infrasound data to maintain surveillance. During this period, satellite data continued to show elevated surface temperatures, and small volcanic clouds were visible in some images.
"By December 6, the continuous tremor signal that had been characteristic of the eruption transitioned into frequent long-period (LP) earthquakes. This change likely indicated that lava effusion had paused or ended. Over the next several days, LP earthquakes and tremor bursts lasting as long as tens of seconds took place frequently, along with occasional harmonic tremor. A partly cloudy Sentinel-2 satellite image from December 10 showed that a light snow dusting covered parts of the intracaldera lava flows, and that only minor steam emissions continued. The weakening of seismic activity, absence of continuous tremor, and apparent cooling of the lava flows further indicated that eruptive activity had ceased.
"AVO detected many ground-coupled airwaves associated with LP earthquakes on December 11, but no other outward signs of unrest were observed in satellite or webcam imagery. This quiescence quickly changed as ash emissions from the intracaldera cone were again observed in Perryville webcam images on December 13 and 16. As cloud cover decreased over the volcano, satellite imagery again showed elevated surface temperatures, indicating a resumption in lava effusion, and also showed small volcanic clouds again extending from the intracaldera cone. This resumption of activity was accompanied by the return of the low-level, nearly continuous seismic tremor, which persisted until December 16, at which point the tremor signal ended and was replaced by many discrete, low-frequency events. Webcam images from Perryville showed minor ash emissions through December 17, after which the volcano was obscured by clouds. Satellite data confirmed that Mount Veniaminof emitted SO2 during the brief unrest in early to mid-December; additional SO2 emissions, possibly from the volcano, were also detected over the Seward Peninsula during this interval, about 966 km [600 mi] to the north.
"A Sentinel-2 satellite image acquired on December 20, 2018, showed no active lava effusion or additional advancement of the active lava flows. Slight fluctuations in seismic tremor amplitude took place from December 21 to 28, and on December 23, strong thermal signals again appeared in satellite data. From December 23 to 24, AVO observed lava-fountain-associated incandescence in webcam images. This activity was brief, however, and by December 27, all satellite, seismic, and webcam data indicated that active lava effusion had slowed, or perhaps stopped completely. From December 27, 2018, through the end of the year, the level of unrest at Mount Veniaminof gradually declined.
"By the end of the eruption, new lava flows covered 600,000 m2 [0.23 mi2] of land. This material came from a cluster of small vents on the upper south flank of a cinder cone within the ice-filled caldera. The flows melted into ice and snow, slowly creating melt depressions around their peripheries. However, no unusual water outflows were observed exiting the caldera through its main drainage, located northwest of the cone. The amount of lava and ash erupted from September 7 to December 27, 2018, resulted in the generation of about 1,200,000 cubic meters (m3 ) [42.4 million cubic feet (ft3)] of lava and 20,000-30,000 m3 [706,000-1,06,000 ft3] of ash, though no aircraft reported encountering ash throughout the eruptive period."
From Orr and others, 2023: "The activity at Mount Veniaminof during 2019 was mostly associated with a prior eruptive period that took place from early September to late December 2018 (Cameron and others, [2023]). Unrest at the volcano declined gradually after this period until it seemed likely that the eruption had paused or ended. On January 4, 2019, AVO lowered the Aviation Color Code and Volcano Alert Level from ORANGE and WATCH to YELLOW and ADVISORY.
"Satellite imagery showed slightly elevated surface temperatures on Mount Veniaminof throughout 2019, although cloud cover frequently impeded observations. The elevated surface temperatures were probably associated with the cooling of lava flows emplaced on the intracaldera cone in 2018 (Cameron and others, 2023). Minor steam emissions were occasionally visible in webcam views from nearby Perryville. Seismicity indicative of minor unrest - primarily low-amplitude tremor and discrete events - continued into April 2019 before finally declining to background levels. AVO lowered the Aviation Color Code and Volcano Alert Level to GREEN and NORMAL on April 30, 2019, after about four months with no significant unrest."

From Orr and others, 2023: "On August 1, 2019, AVO received a PIREP of steaming at Mount Veniaminof’s intracaldera cone, which coincided with a weak tremor signal. These observations marked a small but distinct departure from the background level of unrest at the volcano, and as a result, AVO raised the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY. Weak seismicity and occasional long-period earthquakes continued intermittently throughout most of August, but by the end of the month, the volcano returned to its background activity level. AVO subsequently lowered the Aviation Color Code and Volcano Alert Level to GREEN and NORMAL on August 25, 2019. No additional unrest took place at Mount Veniaminof for the remainder of 2019."

From Orr and others, 2024: "Mount Veniaminof showed no indication of activity at the start of 2021. In response to a prolonged local seismic network outage that started in December 2020, AVO changed the volcano’s Aviation Color Code and Volcano Alert Level from GREEN and NORMAL to UNASSIGNED on January 15, 2021, reflecting the observatory’s limited ability to detect volcanic activity there.
"On March 1, the TROPOspheric Monitoring Instrument (TROPOMI) onboard the Copernicus Sentinel-5 Precursor satellite identified unrest at Mount Veniaminof in the form of elevated sulfur dioxide (SO2) emissions. The TROPOMI sensor measures variations in the wavelength-dependent absorption of ultraviolet energy due to the presence of gases (such as ozone and SO2) and retrieves the amount of gas present in the total atmosphere to account for the observed absorption. On March 2, satellite imagery again showed SO2. Elevated surface temperatures began to appear in satellite imagery early on March 4, and then a few hours later, at 05:13 AKST (14:13 UTC), regional infrasound instruments detected an explosion. Satellite imagery recorded a corresponding ash plume shortly thereafter. An ashy plume from cone A was seen in webcam imagery after sunrise, confirming that an eruption was underway. AVO responded later that morning by increasing the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. A retrospective analysis of high-resolution satellite imagery identified ash deposition near cone A and melting of glacial ice ~1 km [0.6 mi] to its east on February 28, but no signs of activity on February 25, suggesting that the eruption began between those two dates. Figure 18 [in reference] shows a timeline of the activity observed at Mount Veniaminof in 2021.
"The eruption reached its climax on March 4-10, producing moderately to strongly elevated surface temperatures, ash emissions, and frequent explosions detected by infrasound. Several explosions on March 6 were heard and even felt in Perryville, ~35 km [22 mi] away. Webcam and satellite data from this period showed ash emissions from cone A and a steam plume from the growing melt pit east of the cone. Between March 6 and March 10, the ash plumes reached as high as ~15,000 ft (~4,600 m) ASL and traveled as far as 220 km [140 mi] from the volcano. Owing to the height and extent of these ash plumes, local flight restrictions were set in place on March 9. Tephra deposits from the ash plumes were mostly confined to the caldera, but some ash fell outside the caldera on March 8, reaching as far as 22 km [14 mi] from the vent. The ash during this interval was blown predominantly southeastward.
"Lava effusion from vents within the glacial melt pit on the east flank of cone A first appeared in satellite imagery on March 7. The sub-circular melt pit continued to widen as the lava spread away from the flank vents and encompassed an area of nearly 700,000 square meters (m^2) [0.2 square miles] by late March.
Less intense activity characterized the second half of March at Mount Veniaminof. Two seismic stations at the volcano came back online on March 12, allowing AVO geophysicists to detect tremor and LP earthquakes once again. Tremor was detected daily, whereas explosions and ash plumes were detected less frequently. Thermal anomalies from lava effusion were weaker in the second half of the month than in the first half. Lava effusion and minor ash emissions likely continued within the caldera throughout much of this time, although observations were limited to those on clear weather days. Ash plume altitudes remained lower than ~10,000 ft (~3,000 m) ASL. Although not reported, webcam imagery suggested that trace amounts of ash fell in Perryville on March 27, making it the only day during the eruption when a community may have been impacted by ash.
"On April 1, the eruption paused and the volcano showed only slightly elevated surface temperatures, which were probably related to cooling lava flows. The Aviation Color Code and Volcano Alert Level were lowered to YELLOW and ADVISORY on April 2 in response to this decreased activity. However, an ash plume on April 5 prompted AVO to raise the Aviation Color Code and Volcano Alert Level back to ORANGE and WATCH. A second ash plume was observed on April 6. No eruptive activity was observed thereafter, so the Aviation Color Code and Volcano Alert Level were lowered to YELLOW and ADVISORY on April 21, then back to UNASSIGNED on May 12. Elevated surface temperatures detected in the weeks after the pause were most likely related to a warm summit cone and cooling lava flows. Altogether, the three lava flows that erupted within the glacial melt pit covered a combined area of ~2.7×10^4 m^2 [2.9X10^5 sq ft] (Waythomas, 2021).
"AVO workers fully restored the Mount Veniaminof local seismic network during a field campaign in late June and early July. The Aviation Color Code and Volcano Alert Level were consequently changed to GREEN and NORMAL on July 8. Tremor, steam plumes, SO2 emissions, and thermal anomalies were detected in geophysical and remote sensing data shortly before and during the field campaign, which ran from June 28 to July 5. However, the field crew itself observed no noteworthy activity. No further unrest took place at Mount Veniaminof for the remainder of 2021.
"Tephra samples were collected from a snow pit ~2 km [~1.2 mi] east of cone A, adjacent to the melt pit, during the field campaign. Four distinct tephra layers were sampled; each consisted of black and red-oxidized grains intermixed with loose plagioclase crystals. Each layer had a modal grain size of 0.25–0.5 millimeter (mm) [0.01-0.02 in] and a maximum grain size of 2 mm [0.08 in]. One layer also had apparent accretionary lapilli. Petrographic analysis of the samples showed that the phenocrysts, like those sampled from the 2018 eruption (Loewen and others 2021), comprised normally zoned plagioclase, olivine, and rare clinopyroxene. The groundmass was a mixture of microlitic sideromelane, tachylyte, and lithic components. The glass composition was similar to that erupted in 2018, although with slightly lower silica concentrations (like the 2013 eruption glass)."