Pacaya is one of the most active volcanoes in Guatemala, with activity largely consisting of frequent lava flows and Strombolian activity at the Mackenney crater. This report summarizes continued activity during February through July 2019 based on reports by Guatemala's Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH) and Sistema de la Coordinadora Nacional para la Reducción de Desastres (CONRED), visiting scientists, and satellite data.

At the beginning of February activity included Strombolian explosions ejecting material up to 5 to 30 m above the Mackenney crater and a degassing plume up to 300 m. Multiple lava flows were observed throughout the month on the N, NW, and W flanks, reaching 350 m from the crater and resulting in avalanches from the flow fronts. Strombolian activity continued with sporadic to continuous explosions ejecting material 5-75 m above the Mackenney crater. Degassing produced plumes up to 300 m above the crater, and incandescence from the crater and lava flows were seen at night. Daniel Sturgess of Bristol University observed activity on the 24th, noting a 70-m-long lava flow with individual blocks from the front of the flow rolling down the flanks (figure 108). He reported that mild Strombolian explosions occurred every 10-20 minutes and ejected blocks, up to approximately 4 m in diameter, as high as 5-30 m above the crater and towards the northern flank.

Figure 108. An active lava flow on the NW flank of Pacaya on 24 February 2019 with incandescence visible in lower light conditions. Courtesy of Daniel Sturgess, University of Bristol.

Similar activity continued through March with multiple lava flows reaching a maximum of 200 m N and NW, and avalanches descending from the flow fronts. Ongoing Strombolian explosions expelled material up to 75 m above the Mackenney crater. Degassing produced a white-blue plume to a maximum of 900 m above the crater (figure 109) and incandescence was noted some nights.

Figure 109. A degassing plume at Pacaya reaching 350 m above the crater and dispersing to the S on 19 March 2019. Courtesy of CONRED.

During April lava flows continued on the N and NW flanks, reaching a maximum length of 300 m, with avalanches forming from the flow fronts. Degassing formed plumes up to 600 m above the crater that dispersed with various wind directions. Strombolian activity continued with explosions ejecting material up to 40 m above the crater. On the 2nd and 3rd weak rumbles were heard at distances of 4-5 km. Similar activity continued through May with lava flows reaching 300 m to the N, degassing producing plumes up to 600 m above the crater, and Strombolian explosions ejecting material up to 15 m above the crater.

Lava flows continued out to 300 m in length to the N and NW during June (figures 110 and 111). Strombolian activity ejected material up to 30 m above the crater and degassing resulted in plumes that reached 300 m. During July there were multiple active lava flows that reached a maximum of 300 m in length on the N and NW flanks (figure 112). Avalanches generated by the collapse of material at the front of the lava flows were accompanied by explosions ejecting material up to 30 m above the crater.

Figure 110. An active lava flow on Pacaya on 9 June 2019 with incandescent blocks rolling down the flank from the flow front. Courtesy of Paul Wallace, University of Liverpool.

Figure 111. Activity at Pacaya on 22 June 2019 with a degassing plume dispersed to the W and a 300-m-long lava flow. Photos by Miguel Morales, courtesy of CONRED.

Figure 112. Two lava flows were active to the N and NW at Pacaya on 20 July 2019. Photos courtesy of CONRED.

During February through July multiple lava flows and crater activity were detected in Sentinel-2 satellite thermal images (figures 113 and 114) and relatively constant thermal energy was detected by the MIROVA system with a slight decrease in the energy and frequency of anomalies during June (figure 115). The thermal anomalies detected by the MODVOLC system for each month from February through July spanned 6-30, with six during June and 30 during April.

Figure 113. Sentinel-2 thermal satellite images of Pacaya show lava flows to the N and NW during February through April 2019. There was a reduction in visible activity in early March. False color (urban) satellite images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Figure 114. Sentinel-2 thermal satellite images of Pacaya showing lava flow and hot avalanche activity during June and July 2019. False color (urban) satellite images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Figure 115. MIROVA log radiative power plot of MODIS thermal infrared at Pacaya during October 2018 through July 2019. Detected thermal energy is relatively stable with a decrease through June and subsequent increase during July. Courtesy of MIROVA.

Geologic Background. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié 21-72, Zona 13, Guatemala City, Guatemala (URL: http://conred.gob.gt/www/index.php); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Daniel Sturgess, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, United Kingdom (URL: http://www.bristol.ac.uk/earthsciences/); Paul Wallace, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, 4 Brownlow Street, Liverpool L69 3GP, United Kingdom (URL: https://www.liverpool.ac.uk/environmental-sciences/staff/paul-wallace/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Frequent historical eruptions at Volcán de Colima date back to the 16th century and include explosive activity, lava flows, and large debris avalanches. The most recent eruptive episode began in January 2013 and continued through March 2017. Previous reports have covered activity involving ash plumes with extensive ashfall, lava flows, lahars, and pyroclastic flows (BGVN 41:01 and 42:08). In late April 2019, increased seismicity related to volcanic activity began again. This report covers activity through July 2019. The primary source of information was the Centro Universitario de Estudios e Investigaciones de Vulcanologia, Universidad de Colima (CUEIV-UdC).

On 11 May 2019, CUEIV-UdC reported an explosion that was recorded by several monitoring stations. A thermal camera located south of Colima captured thermal anomalies associated with the explosion as well as intermittent degassing, which mainly consisted of water vapor (figure 131). A report from the Unidad Estatal de Protección Civil de Colima (UEPCC), and seismic and infrasound network data from CUEIV-UdC, recorded about 60 high-frequency events, 16 landslides, and 14 low-magnitude explosions occurring on the NE side of the crater during 11-24 May. Drone imagery showed fumarolic activity occurring on the inner wall of this crater on 22 May (figure 132).

Figure 131. Gas emissions from Colima during the 11 May 2019 eruption as seen from the Naranjal station. Courtesy of CUEIV-UdC (Boletin Seminal de la Actividad del Volcan de Colima 17 mayo 2019 no 121).

Figure 132. A drone photo showing fumarolic activity occurring within the NE wall of the crater at Colima on 22 May 2019. Courtesy of CUEIV-UdC (Boletin Seminal de la Actividad del Volcan de Colima 24 mayo 2019 no 122).

Small explosions and gas-and-steam emissions continued intermittently through mid-July 2019 concentrated on the NE side of the crater. An overflight on 9 July 2019 revealed that subsidence from the consistent activity slightly increased the diameter of the vent; other areas within the crater also showed evidence of subsidence and some collapsed material on the outer W wall (figure 133). During the weeks of 19 and 26 July 2019, monitoring cameras and seismic data recorded eight lahars.

Figure 133. A drone photo of the crater at Colima on 8 July 2019 shows continuing fumarolic activity and evidence of a collapsed wall on the W exterior side. Courtesy of CUEIV-UdC (Boletin Seminal de la Actividad del Volcan de Colima 12 julio 2019 no 129).

Geologic Background. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Information Contacts: Centro Universitario de Estudios e Investigaciones de Vulcanologia, Universidad de Colima (CUEIV-UdC), Colima, Col. 28045, Mexico; Centro Universitario de Estudios Vulcanologicos y Facultad de Ciencias de la Universidad de Colima, Avenida Universidad 333, Colima, Col. 28045, Mexico (URL: http://portal.ucol.mx/cueiv/); Unidad Estatal de Protección Civil, Colima, Roberto Esperón No. 1170 Col. de los Trabajadores, C.P. 28020, Mexico (URL: http://www.proteccioncivil.col.gob.mx/).

Masaya, in Nicaragua, contains a lava lake found in the Santiago Crater which has remained active since its return in December 2015 (BGVN 41:08). In addition to this lava lake, previous volcanism included explosive eruptions, lava flows, and gas emissions. Activity generally decreased during March-July 2019, including the number and frequency of thermal anomalies, lava lake levels, and gas emissions. The primary source of information for this report comes from the Instituto Nicareguense de Estudios Territoriales (INETER).

On 21 July 2019 a small explosion in the Santiago Crater resulted in some gas emissions and an ash cloud drifting WNW. In addition to the active lava lake (figure 77), monthly reports from INETER noted that thermal activity and gas emissions (figure 78) were decreasing.

Figure 77. Active lava lake visible in the Santiago Crater at Masaya on 27 June 2019. Photo by Sheila DeForest (Creative Commons BY-SA license).

Figure 78. Gas emissions coming from the Santiago Crater at Masaya on 29 June 2019. Photo by Sheila DeForest (Creative Commons BY-SA license).

On 15 May and 22 July 2019, INETER scientists used a FLIR SC620 thermal infrared camera to measure temperatures of fumaroles on the Santiago Crater. In May 2019 the temperature of fumaroles had decreased by 48°C since the previous month. Between May and July 2019 fumarole temperatures continued to decline; temperatures ranged from 90° to 136°C (figure 79). Compared to May 2019 these temperatures are 3°C lower. INETER reports that the level of the lava lake has been slowly dropping during this reporting period.

Figure 79. FLIR (forward-looking infrared) and visible images of the Santiago Crater at Masaya showing fumarole temperatures ranging from 90° to 136°C. The scale in the center shows the range of temperatures in the FLIR image. Courtesy of INETER (March 2019 report).

According to MIROVA (Middle InfraRed Observation of Volcanic Activity) data from MODIS satellite instruments, frequent thermal anomalies were recorded from mid-March through early May 2019, with little to no activity from mid-May to July 2019 (figure 80). Sentinel-2 thermal images show high temperatures in the active lava lake on 10 March 2019 (figure 81). Thermal energy detected by the MODVOLC algorithm showed 14 hotspot pixels with the most number of hotspots (7) occurring in March 2019.

Figure 80. Thermal anomalies were relatively constant at Masaya from early September 2018 through early May 2019 and then abruptly decreased until mid-June 2019 as recorded by MIROVA. Courtesy of MIROVA.

Figure 81. Sentinel-2 thermal satellite image showing a detected heat signature from the active lava lake at Masaya on 10 March 2019. The lava lake is visible (bright yellow-orange). Approximate diameter of the crater containing the lava lake is 500 m. Thermal (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Sheila DeForest (URL: https://www.facebook.com/sheila.deforest).

The acid lake of Rincón de la Vieja's active crater has generated intermittent weak phreatic explosions regularly since 2011, continuing during the past year through at least August 2019. The volcano is monitored by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), and the information below comes from its weekly bulletins between 4 March and 2 September 2019. Clouds often prevented webcam and satellite views. The current report describes activity from March through July 2019.

OVSICORI-UNA reported that weak events occurred on 19 March at 1851 and on 29 March 2019 at 2043. A two-minute-long phreatic explosion on 1 April at 0802 produced a plume that rose 600 m above the crater rim. Continuous emissions were visible during 3-4 April, rising 200 m above the crater rim. On 3 April, at 1437, a small explosion was detected. An explosion on 10 April at 0617 produced a gas-and-steam plume that rose 1 km above the crater rim and drifted SE. On 12 April at 0643, a plume rose 500 m. Another event took place at 0700 on 13 April, although poor weather conditions prevented visual observations. On 14 April, OVSICORI-UNA noted that aerial photographs showed a milky-gray acid lake at a relatively low water level with convection cells of several tens meters of diameter in the center and eastern parts of the lake.

According to an OVSICORI-UNA bulletin, a small phreatic explosion occurred on 1 May. Another explosion on 11 May at 0720 produced a white gas-and-steam plume that rose 600 m above the crater rim. Phreatic explosions were recorded on 14 May at 1703 and on 17 May at 0357, though dense fog prevented visual confirmation of both events with webcams. On 15 May a local observer noted a diffuse plume of steam and gas, material rising from the crater, and photographed milky-gray deposits on the N part of the crater rim ejected from the event the day before. A major explosion occurred on 24 May.

OVSICORI-UNA recorded a significant phreatic 10-minute-long explosion that began on 11 June at 0343, but plumes were not visible due to weather conditions. No further phreatic events were reported in July.

Seismic activity was very low during the reporting period, and there was no significant deformation. Short tremors were frequent toward the end of April, but were only periodic in May and June; tremor almost disappeared in July. A few long-period earthquakes were recorded, and volcano-tectonic earthquakes were even less frequent.

Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 km3 Río Blanca tephra about 3500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/, https://www.facebook.com/OVSICORI/).

Sakurajima rises from Kagoshima Bay, which fills the Aira Caldera near the southern tip of Japan's Kyushu Island. Frequent explosive and occasional effusive activity has been ongoing for centuries. The Minamidake summit cone has been the location of persistent activity since 1955; the Showa crater on its E flank has also been intermittently active since 2006. Numerous explosions and ash-bearing emissions have been occurring each month at either Minamidake or Showa crater since the latest eruptive episode began in late March 2017. This report covers ongoing activity from January through June 2019; the Japan Meteorological Agency (JMA) provides regular reports on activity, and the Tokyo VAAC (Volcanic Ash Advisory Center) issues tens of reports each month about the frequent ash plumes.

From January to June 2019, ash plumes and explosions were usually reported multiple times each week. The quietest month was June with only five eruptive events; the most active was March with 29 (table 21). Ash plumes rose from a few hundred meters to 3,500 m above the summit during the period. Large blocks of incandescent ejecta traveled as far as 1,700 m from the Minamidake crater during explosions in February and April. All the activity originated in the Minamidake crater; the adjacent Showa crater only had a mild thermal anomaly and fumarole throughout the period. Satellite imagery identified thermal anomalies inside the Minamidake crater several times each month.

Table 21. Monthly summary of eruptive events recorded at Sakurajima's Minamidake crater in Aira caldera, January-June 2019. The number of events that were explosive in nature are in parentheses. No events were recorded at the Showa crater during this time. Data courtesy of JMA (January to June 2019 monthly reports).

There were eight eruptive events reported by JMA during January 2019 at the Minamidake summit crater of Sakurajima. They occurred on 3, 6, 7, 9, 17, and 19 January (figure 76). Ash plume heights ranged from 600 to 2,100 m above the summit. The largest explosion, on 9 January, generated an ash plume that rose 2,100 m above the summit crater and drifted E. In addition, incandescent ejecta was sent 800-1,100 m from the summit. Incandescence was visible at the summit on most clear nights. During an overflight on 18 January no significant changes were noted at the crater (figure 77). Infrared thermal imaging done on 29 January indicated a weak thermal anomaly in the vicinity of the Showa crater on the SE side of Minamidake crater. The Kagoshima Regional Meteorological Observatory (KRMO) (11 km WSW) recorded ashfall there during four days of the month. Satellite imagery indicated thermal anomalies inside Minamidake on 7 and 27 January (figure 77).

Figure 76. Incandescent ejecta and ash emissions characterized activity from Sakurajima volcano at Aira during January 2019. Left: A webcam image showed incandescent ejecta on the flanks on 9 January 2019, courtesy of JMA (Explanation of volcanic activity in Sakurajima, January 2019). Right: An ash plume rose hundreds of meters above the summit, likely also on 9 January, posted on 10 January 2019, courtesy of Mike Day.

Figure 77. The summit of Sakurajima consists of the larger Minamidake crater and the smaller Showa crater on the E flank. Left: The Minamidake crater at the summit of Sakurajima volcano at Aira on 18 January 2019 seen in an overflight courtesy of JMA (Explanation of volcanic activity in Sakurajima, March 2019). Right: Two areas of thermal anomaly were visible in Sentinel-2 satellite imagery on 27 January 2019. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

Activity increased during February 2019, with 15 eruptive events reported on days 1, 3, 7, 8, 10, 13, 14, 17, 22, 24, and 27. Ash plume heights ranged from 600-2,300 m above the summit, and ejecta was reported 300 to 1,700 m from the crater in various events (figure 78). KRMO reported two days of ashfall during February. Satellite imagery identified thermal anomalies at the crater on 6 and 26 February, and ash plumes on 21 and 26 February (figure 79).

Figure 78. An explosion from Sakurajima at Aira on 7 February 2019 sent ejecta up to 1,700 m from the Minamidake summit crater. Courtesy of JMA (Explanation of volcanic activity in Sakurajima, February 2019).

Figure 79. Thermal anomalies and ash emissions were captured in Sentinel-2 satellite imagery on 6, 21, and 26 February 2019 originating from Sakurajima volcano at Aira. Top: Thermal anomalies within the summit crater were visible underneath steam and ash plumes on 6 and 26 February (closeup of bottom right photo). Bottom: Ash emissions on 21 and 26 February drifted SE from the volcano. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

The number of eruptive events continued to increase during March 2019; there were 29 events reported on numerous days (figures 80 and 81). An explosion on 14 March produced an ash plume that rose 3,500 m above the summit and drifted E. It also produced ejecta that landed 800-1,100 m from the crater. During an overflight on 26 March a fumarole was the only activity in Showa crater. KRMO reported 14 days of ashfall during the month. Satellite imagery identified an ash plume on 13 March and a thermal anomaly on 18 March (figure 82).

Figure 80. A large ash emission from Sakurajima volcano at Aira was photographed by a tourist on the W flank and posted on 1 March 2019. Courtesy of Kratü.

Figure 81. An ash plume from Sakurajima volcano at Aira on 18 March 2019 produced enough ashfall to disrupt the trains in the nearby city of Kagoshima according to the photographer. Image taken from about 20 km away. Courtesy of Tim Board.

Figure 82. An ash plume drifted SE from the summit of Sakurajima volcano at Aira on 13 March (left) and a thermal anomaly was visible inside the Minamidake crater on 18 March 2019 (right). "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

A decline in activity to only ten eruptive events on days 7, 13, 17, 22, and 25 was reported by JMA for April 2019. An explosion on 7 April sent ejecta up to 1,700 m from the crater. Another explosion on 13 April produced an ash plume that rose 2,200 m above the summit. Most of the eruptive events at Sakurajima last for less than 30 minutes; on 22 April two events lasted for almost an hour each producing ash plumes that rose 1,400 m above the summit. Ashfall at KRMO was reported during seven days in April. Two distinct thermal anomalies were visible inside the Minamidake crater on both 12 and 27 April (figure 83).

Figure 83. Two thermal anomalies were present inside Minamidake crater at the summit of Sakurajima volcano at Aira on 12 (left) and 27 (right) April 2019. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

There were 15 eruptive events during May 2019. An event that lasted for two hours on 12 May produced an ash plume that rose 2,900 m from the summit and drifted NE (figure 84). The Meteorological Observatory reported 14 days with ashfall during the month. Two thermal anomalies were present in satellite imagery in the Minamidake crater on both 17 and 22 May.

Figure 84. An ash plume rose 2,900 m above the summit of Sakurajima at Aira on 12 May 2019 (left); incandescent ejecta went 1,300 m from the summit crater on 13 May. Courtesy of JMA (Explanation of volcanic activity in Sakurajima, May 2019).

During June 2019 five eruptive events were reported, on 11, 13, and 24 June; the event on 11 June lasted for almost two hours, sent ash 2,200 m above the summit, and produced ejecta that landed up to 1,100 m from the crater (figure 85). Five days of ashfall were reported by KRMO.

Figure 85. A large ash plume on 11 June 2019 rose 2,200 m above the summit of Sakurajima volcano at Aira. Courtesy of Aone Wakatsuki.

Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Mike Day, Minnesota, Twitter (URL: https://twitter.com/MikeDaySMM, photo at https://twitter.com/MikeDaySMM/status/1083489400451989505/photo/1); Kratü, Twitter (URL: https://twitter.com/TalesOfKratue, photo at https://twitter.com/TalesOfKratue/status/1101469595414589441/photo/1); Tim Board, Japan, Twitter (URL: https://twitter.com/Hawkworld_, photo at https://twitter.com/Hawkworld_/status/1107789108754038789); Aone Wakatsuke, Twitter (URL: https://twitter.com/AoneWakatsuki, photo at https://twitter.com/AoneWakatsuki/status/1138420031258210305/photo/3).

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung on Bali remained quiet until a new eruption began in November 2017 (BGVN 43:01). Lava emerged into the summit crater at the end of November and intermittent ash plumes rose as high as 3 km above the summit through the end of the year. Activity continued throughout 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the slow effusion of the lava within the summit crater (BGVN 43:08, 44:02). Information about the ongoing eruptive episode comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the ongoing eruption from February through May 2019.

Intermittent but increasingly frequent and intense explosions with ash emissions and incandescent ejecta characterized activity at Agung during February through May 2019. During February, explosions were reported three times; events on seven days in March were documented with ash plumes and ashfall in surrounding villages. Five significant events occurred during April; two involved incandescent ejecta that traveled several kilometers from the summit, and ashfall tens of kilometers from the volcano. Most of the five significant events reported in May involved incandescent ejecta and ashfall in adjacent villages; air traffic was disrupted during the 24 May event. Ash plumes in May reached altitudes over 7 km multiple times. Thermal activity increased steadily during the period, according to both the MIROVA project (figure 44) and MODVOLC thermal alert data. MAGMA Indonesia reported at the end of May 2019 that the volume of lava within the summit crater remained at about 25 million m³; satellite information indicated continued thermal activity within the crater. Alert Level III (of four levels) remained in effect throughout the period with a 4 km exclusion radius around the volcano.

Figure 44. Thermal activity at Agung from 4 September 2018 through May 2019 was variable. The increasing frequency and intensity of thermal events was apparent from February-May. Courtesy of MIROVA.

Steam plumes rose 30-300 m high daily during February 2019. The Agung Volcano Observatory (AVO) and PVMBG issued a VONA on 7 February (UTC) reporting an ash plume, although it was not visible due to meteoric cloud cover. Incandescence, however, was observed at the summit from webcams in both Rendang and Karangasem City (16 km SE). The seismic event associated with the explosion lasted for 97 seconds. A similar event on 13 February was also obscured by clouds but produced a seismic event that lasted for 3 minutes and 40 seconds, and ashfall was reported in the village of Bugbug, about 20 km SE. On 22 February a gray ash plume rose 700 m from the summit during a seismic event that lasted for 6 minutes and 20 seconds (figure 45). The Darwin VAAC reported the plume visible in satellite imagery moving W at 4.3 km altitude. It dissipated after a few hours, but a hotspot remained visible about 10 hours later.

Figure 45. An ash plume rose from the summit of Agung on 22 February 2019, viewed from the Besakih temple, 7 km SW of the summit. Courtesy of PunapiBali.

Persistent steam plumes rose 50-500 m from the summit during March 2019. An explosion on 4 March was recorded for just under three minutes and produced ashfall in Besakih (7 km SW); no ash plume was observed due to fog. A short-lived ash plume rose to 3.7 km altitude and drifted SE on 8 March (UTC) 2019. The seismic event lasted for just under 4 minutes. Ash emissions were reported on 15 and 17 March to 4.3 and 3.7 km altitude, respectively, drifting W (figure 46). Ashfall from the 15 March event spread NNW and was reported in the villages of Kubu (6 km N), Tianyar (14 km NNW), Ban, Kadundung, and Sukadana. MAGMA Indonesia noted that two explosions on the morning of 17 March (local time) produced gray plumes; the first sent a plume to 500 m above the summit drifting E and lasted for about 40 seconds, while the second plume a few hours later rose 600 m above the crater and lasted for 1 minute and 16 seconds. On 18 March an ash plume rose 1 km and drifted W and NW. An event on 20 March was measured only seismically by PVMBG because fog prevented observations. An eruption on 28 March produced an ash plume 2 km high that drifted W and NW. The seismic signal for this event lasted for about two and a half minutes. The Darwin VAAC reported the ash plume at 5.5 km altitude, dissipating quickly to the NW. No ash was visible four hours later, but a thermal anomaly remained at the summit (figure 47). Ashfall was reported in nearby villages.

Figure 46. Ash plumes from Agung on 15 (left) and 17 (right) March 2019 resulted in ashfall in communities 10-20 km from the volcano. Courtesy of PVMBG and MAGMA Indonesia (Information on G. Agung Eruption, 15 March 2019 and Gunung Agung Eruption Press Release March 17, 2019).

Figure 47. A thermal anomaly was visible through thick cloud cover at the summit of Agung on 29 March 2019 less than 24 hours after a gray ash plume was reported 2,000 m above the summit. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

The first explosion of April 2019 occurred on the 3rd (UTC); PVMBG reported the dense gray ash plume 2 km above the summit drifting W. A few hours later the Darwin VAAC raised the altitude to 6.1 km based on infrared temperatures in satellite imagery. The seismic signal lasted for three and a half minutes and the explosion was heard at the PGA Post in Rendang (12 km SW). Incandescent material fell within a radius of 2-3 km, mainly on the S flank (figure 48). Ashfall was reported in the villages of Telungbuana, Badeg, Besakih, Pempatan, Teges, and Puregai on the W and S flanks (figure 49). An explosion on 11 April also produced a dense gray ash plume that rose 2 km above the summit and drifted W. A hotspot remained about six hours later after the ash dissipated.

Figure 48. Incandescent ejecta appeared on the flanks of Agung after an eruption on 4 April 2019 (local time) as viewed from the observation post in Rendang (8 km SW). Courtesy of Jamie Sincioco.

Figure 49. Ashfall in a nearby town dusted mustard plants on 4 April 2019 from an explosion at Agung the previous day. Courtesy of Pantau.com (Photo: Antara / Nyoman Hendra).

PVMBG reported an eruption visible in the webcam early on 21 April (local time) that rose to 5.5 km altitude and drifted SW. The ash spread W and S and ash fell around Besakih (7 km SW), Rendang (8 km SW), Klungkung (25 km S), Gianyar (20 km WSW), Bangli (17 km WNW), Tabanan (50 km WSW), and at the Ngurah Rai-Denpasar Airport (60 km SW). About 15 hours later a new explosion produced a dense gray ash plume that rose to 3 km above the summit and produced incandescent ejecta in all directions as far as 3 km away (figure 50). The ash spread to the S and ashfall was reported in Besakih, Rendang, Sebudi (6 km SW), and Selat (12 km SSW). Both of the explosions were heard in Rendang and Batulompeh. The incandescent ejecta from the explosions remained within the 4-km exclusion zone. A satellite image on 23 April showed multiple thermal anomalies within the summit crater (figure 51). A dense gray plume drifted E from Agung on 29 April (30 April local time) at 4.6 km altitude. It was initially reported by ground observers, but was also visible in multispectral satellite imagery for about six hours before dissipating.

Figure 50. An explosion at Agung on 21 April 2019 sent incandescent eject 3,000 m from the summit. Courtesy of MAGMA Indonesia (Gunung Agung Eruption Press Release April 21, 2019).

Figure 51. Multiple thermal anomalies were still present within the summit crater of Agung on 23 April 2019 after two substantial explosions produced ash and incandescent ejecta around the summit two days earlier. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG reported an eruption on 3 May 2019 that was recorded on a seismogram with a signal that lasted for about a minute. Satellite imagery reported by the Darwin VAAC showed a growing hotspot and possible ash near the summit at 4.3 km altitude moving NE. A few days later, on 6 May, a gray ash plume rose to 5.2 km altitude and drifted slowly W before dissipating; it was accompanied by a seismic signal that lasted for about two minutes. Explosions on 12 and 18 May produced significant amounts of incandescent ejecta (figure 52). The seismic signal for the 12 May event lasted for about two minutes; no plume was observed due to fog, but incandescent ejecta was visible on the flanks and the explosion was heard at Rendang. The Darwin VAAC reported an ash plume from the explosion on 17 May (18 May local time) at 6.1 km altitude in satellite imagery moving E. They revised the altitude a short while later to 7.6 km based on IR temperature and movement; the plume drifted N, NE, and E in light and variable winds. A few hours after that it was moving NE at 7.6 km altitude and SE at 5.5 km altitude; this lasted for about 12 hours until it dissipated. Ashfall was reported in villages downwind including Cutcut, Tongtongan, Bonyoh (20 km WNW), and Temakung.

Figure 52. Explosions on 12 (left) and 18 (right) May (local time) 2019 produced substantial ejecta on the flanks of Agung visible from a distance of 10 km or more in PVMBG webcams. The ash plume from the 18 May event resulted in ashfall in numerous communities downwind. Courtesy of PVMBG (Information Eruption G. Agung, May 13, 2019, Information Eruption G. Agung, May 18, 2019).

The initial explosion on 18 May was captured by a webcam at a nearby resort and sent incandescent ejecta hundreds of meters down the NE flank within 20 seconds (figure 53). Satellite imagery on 3, 8, 13, and 18 May indicated multiple thermal anomalies growing stronger at the summit. All of the images were captured within 24 hours of an explosive event reported by PVMBG (figure 54).

Figure 53. The 18 May 2019 explosion at Agung produced an ash plume that rose to over 7 km altitude and large bombs of incandescent material that traveled hundreds of meters down the NE flank within the first 20 seconds of the explosion. Images taken from a private webcam located 12 km NE. Courtesy of Volcanoverse, used with permission.

Figure 54. Satellite images from 3, 8, 13, and 18 May 2019 at Agung showed persistent and increasing thermal anomalies within the summit crater. All images were captured within 24 hours of explosions reported by PVMBG. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG issued a VONA on 24 May 2019 reporting a new ash emission. They indicated that incandescent fragments were ejected 2.5-3 km in all directions from the summit, and the seismic signal lasted for four and a half minutes (figure 55). A dense gray ash plume was observed from Tulamben on the NE flank rising 2 km above the summit. Satellite imagery indicated that the plume drifted SW and ashfall was reported in the villages of Besakih, Pempatan, Menanga, Sebudi, Muncan, Amerta Bhuana, Nongan, Rendang, and at the Ngurah Rai Airport in Denpassar. Additionally, ashfall was reported in the districts of Tembuku, Bangli, and Susut (20 km SW). The Darwin VAAC reported an ash plume visible in satellite imagery at 4.6 km altitude along with a thermal anomaly and incandescent lava visible in webcam imagery. The remains of the ash plume were about 170 km S of the airport in Denpasar (60 km SW) and had nearly dissipated 18 hours after the event. According to a news article several flights to and from Australia were cancelled or diverted, though the International Gusti Ngurah Rai (IGNR) airport was not closed. On 31 May another large explosion produced the largest ash plume of the report period, rising more than 2 km above the summit (figure 56). The Darwin VAAC reported its altitude as 8.2 km drifting ESE visible in satellite data. It split into two plumes, one drifted E at 8.2 km and the other ESE at 6.1 km altitude, dissipating after about 20 hours.

Figure 55. A large explosion at Agung on 24 May 2019 produced incandescent ejecta that covered all the flanks and dispersed ash to many communities to the SW. Courtesy of PVMBG (Gunung Agung Eruption Press Release 24 May 2019 20:38 WIB, Kasbani, Ir., M.Sc.).

Figure 56. An explosion at Agung on 31 May 2019 sent an ash plume to 8.2 km altitude, the highest for the report period. Courtesy of Sutopo Purwo Nugroho, BNPB.

Geologic Background. Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); The Jakarta Post, Mount Agung eruption disrupts Australian flights, (URL: https://www.thejakartapost.com/news/2019/05/25/mount-agung-eruption-disrupts-australian-flights.html); PunapiBali (URL: http://punapibali.com/, Twitter: https://twitter.com/punapibali, image at https://twitter.com/punapibali/status/1098869352588288000/photo/1); Jamie S. Sincioco, Phillipines (URL: Twitter: https://twitter.com/jaimessincioco. Image at https://twitter.com/jaimessincioco/status/1113765842557104130/photo/1); Pantau.com (URL: https://www.pantau.com/berita/erupsi-gunung-agung-sebagian-wilayah-bali-terpapar-hujan-abu?utm_source=dlvr.it&utm_medium=twitter); Volcanoverse (URL: https://www.youtube.com/channel/UCi3T_esus8Sr9I-3W5teVQQ); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN ).

Frequently active, Indonesia's Mount Kerinci on Sumatra has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838. Intermittent explosions with ash plumes, usually multiple times per month, have characterized activity since April 2018. Similar activity continued during February-May 2019, the period covered in this report with information provided primarily by the Indonesian volcano monitoring agency, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), MAGMA Indonesia, notices from the Darwin Volcano Ash Advisory Center (Darwin VAAC), and satellite data. PVMBG has maintained an Alert Level II (of 4) at Kerinci for several years.

On 13 February 2019 the Kerinci Volcano Observatory (KVO), part of PVMBG, noted a brownish-white ash emission that was drifting NE about 400 m above the summit. The seismicity during the event was dominated by continuous volcanic tremor. A brown ash emission was reported on 7 March 2019 that rose to 3.9 km altitude and drifted NE. Ash also drifted 1,300 m down the SE flank. Another ash plume the next morning drifted W at 4.5 km altitude, according to KVO. On 10, 11, and 13 March KVO reported brown ash plumes drifting NE from the summit at about 4.0-4.3 km altitude. The Darwin VAAC observed continuous ash emissions in satellite imagery on 15 March drifting W at 4.3 m altitude that dissipated after about 3 hours (figure 10). A gray ash emission was reported on 19 March about 600 m above the summit drifting NE; local news media noted that residents of Kayo Aro reported emissions on both 18 and 19 March (figure 11). An ash emission appeared in satellite imagery on 25 March (figure 10). On 30 March the observatory reported two ash plumes; a brown emission at 0351 UTC and a gray emission at 0746 UTC that both drifted NE at about 4.4 km altitude and dissipated within a few hours. PVMBG reported another gray ash plume the following day at a similar altitude.

Figure 10. Sentinel-2 satellite imagery of Kerinci from 15 (left) and 25 (right) March 2019 showed evidence of ash plumes rising from the summit. Kerinci's summit crater is about 500 m wide. "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.

Figure 11. Dense ash plumes from Kerinci were reported by local news media on 18 and 19 March 2019. Courtesy of Nusana Jambi.

Activity continued during April with a brown ash emission reported on 3 April by several different agencies; the Darwin VAAC and PVMBG daily reports noted that the plume was about 500 m above the summit (4.3 km altitude) drifting NE. KVO observed two brown ash emissions on 13 April (UTC) that rose to 4.2 km altitude and drifted NE. Satellite imagery showed minor ash emissions from the summit on 14 April; steam plumes 100-500 m above the summit characterized activity for the remainder of April (figure 12).

Figure 12. A dilute ash emission rose from the summit of Kerinci on 14 April 2019 (left); only steam emissions were present on a clear 29 April in Sentinel-2 imagery (right). "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.

Ashfall on the NE and S flanks within 7 km of the volcano was reported on 2 May 2019. According to a news article, at least five villages were affected late on 2 May, including Tanjung Bungo, Sangir, Sangir Tengah, Sungai Rumpun, and Bendung Air (figures 13 and 14). The smell of sulfur was apparent in the villages. Brown ash emissions were observed on 3 and 4 May that rose to 4.6 and 4.1 km altitude and drifted SE. The Darwin VAAC reported an emission on 5 May, based on a pilot report, that rose to 6.7 km altitude and drifted NE for about an hour before dissipating. A brown ash emission on 10 May rose 700 m above the summit and drifted SE. Satellite imagery captured ash emissions from the summit on 14 and 24 May (figure 15). For the remainder of the month, 300-700-m-high dense steam plumes were noted daily until PVMBG reported white and brown plumes on 26 and 27 May rising 500-1,000 m above the summit. Although thermal anomalies were not reported during the period, persistent weak SO₂ emissions were identified in TROPOMI instrument satellite data multiple times per month (figure 16).

Figure 13. Ashfall was reported from five villages on the flanks of Kerinci on 2 May 2019. Courtesy of Uzone.

Figure 14. An ash plume at Kerinci rose hundreds of meters on 2 May 2019; ashfall was reported in several nearby villages. Courtesy of Kerinci Time.

Figure 15. Ash emissions from Kerinci were captured in Sentinel-2 satellite imagery on 14 (left) and 24 (right) May 2019. The summit crater is about 500 m wide. "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.

Figure 16. Weak SO2 anomalies from Kerinci emissions were captured by the TROPOMI instrument on the Sentinel-5P satellite multiple times each month from February to May 2019. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Nuansa Jambi, Informasi Utama Jambi: (URL: https://nuansajambi.com/2019/03/20/gunung-kerinci-semburkan-asap-tebal/); Kerinci Time (URL: https://kerincitime.co.id/gunung-kerinci-semburkan-abu-vulkanik.html); Uzone.id (URL: https://news.uzone.id/gunung-kerinci-erupsi-5-desa-tertutup-abu-tebal).

Suwanosejima is an active volcanic island south of Japan in the Ryuku islands with recent activity centered at Otake crater. The current eruption began in October 2004 and activity has mostly consisted of small ash plumes, ballistic ejecta, and visible incandescence at night. This report summarizes activity during January through June 2019 and is based on reports by the Japan Meteorological Agency (JMA), and various satellite data.

Thermal activity recorded by the MIROVA system was low through January and February after a decline in November (figure 36), shown in Sentined-2 thermal infrared imagery as originating at a vent in the Otake crater (figure 37). During January an explosive event was observed at 1727 on the 3rd, producing a gray plume that rose 600 m above the crater. A white gas-and-steam plume rose to 1.5 km above the crater and nighttime incandescence was observed throughout the month. Reduced activity continued through February with no reported explosive eruptions and light gray plumes up to 900 m above the crater. Incandescence continued to be recorded at night using a sensitive surveillance camera.

Figure 36. MIROVA log radiative power plot of MODIS thermal infrared data at Suwanosejima during September 2018 through June 2019. There was reduced activity in 2019 with periods of more frequent anomalies during March and June. Courtesy of MIROVA.

Figure 37. A Sentinel-2 thermal satellite image shows Suwanosejima with the active Otake crater in the center with elevated temperatures shown as bright orange/yellow. There is a light area next to the vent that may be a gas plume. False color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

There was an increase in thermal energy detected by the MIROVA system in mid-March and there was a MODVOLC thermal alert on the 15th. Occasional small explosions occurred but no larger explosive events were recorded. A white plume was noted on the 27th rising to 900 m above the crater and an event at 1048 on the 30th produced a light-gray plume that rose to 800 m. Incandescence was only observed using a sensitive camera at night (figure 38).

Figure 38. Incandescence from the Suwanosejima Otake crater reflecting in clouds above the volcano. Courtesy of JMA (Volcanic activity of Suwanosejima March 2019).

No explosive events were observed through April. A white gas-and-steam plume rose to 1,200 m above the crater on the 19th and incandescence continued intermittently. Minor explosions were recorded on 5, 30, and 31 May, but no larger explosive events were observed during the month. The event on the 30th produced ash plume that reached 1.1 km above the crater. Similar activity continued through June with one explosive event occurring on the 2nd. Overall, there was a reduction in the number of ash plumes erupted during this period compared to previous months (figure 39).

Figure 39. Observed activity at Suwanosejima for the year ending in July 2019. The black vertical bars represent steam, gas, or ash plume heights (scale in meters on the left axis), yellow diamonds represent incandescence observed in webcams, gray volcano symbols along the top are explosions accompanied by ash plumes, red volcano symbols represent large explosions with ash plumes. Courtesy of JMA (Volcanic activity of Suwanosejima June 2019).

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

The Great Sitkin volcano is located about 40 km NE of Adak Island in the Aleutian Islands and has had a few short-lived eruptions over the past 100 years. Prior to the latest activity in early June 2019 described below, small phreatic explosions occurred in June and August 2018 (BGVN 43:09). An eruption in 1974 produced a lava dome in the center of the crater. The Alaska Volcano Observatory (AVO) is the primary source of information for this September 2018-June 2019 reporting period.

Low-level unrest occurred from September 2018 through February 2019 with slightly elevated seismic activity (figure 6). Small explosions were seismically detected by AVO on 30 October, 5 and 16 November, and 11 December 2018, but they were not seen in regional infrasound data and satellite data did not show an ash cloud.

On 1, 7, and 9 June 2019, AVO reported small steam explosions as well as slightly elevated seismic activity. Steam plumes and surficial evidence of an explosion were not observed during these events. On 18 June 2019 weakly elevated surface temperatures were recorded, field crews working on Adak observed some steam emissions, and a gas flight was conducted. Elevated concentrations of carbon dioxide detected above the lava dome were likely associated with the steam explosions earlier in the month (figures 7 and 8). From 23 June through the end of the month seismicity began to decline back to background levels.

Figure 6. A steam plume was seen at the summit of Great Sitkin on 7 December 2018. Photo by Andy Lewis and Bob Boyd; courtesy of AVO/USGS.

Figure 7. Some degassing was observed on the southern flank of the Great Sitkin during an overflight on 18 June 2019. Photo by Laura Clor; image courtesy of AVO/USGS.

Figure 8. View of Great Sitkin with white plumes rising from the summit on 20 June 2019. Photo by Laura Clor, courtesy of AVO/USGS.

Geologic Background. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/).

Ibu volcano on Halmahera island in Indonesia began the current eruption episode on 5 April 2008. Since then, activity has largely consisted of small ash plumes with less frequent lava flows, lava dome growth, avalanches, and larger ash plumes up to 5.5 km above the crater. This report summarizes activity during December 2018 through June 2019 and is based on Volcano Observatory Notice for Aviation (VONA) reports by MAGMA Indonesia, reports by Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and Badan Nasional Penanggulangan Bencana (BNPB), and various satellite data.

During December PVMBG reported ash plumes ranging from 200 to 800 m above the crater. There were 11 MODVOLC thermal alerts that registered during 1-12 December. An explosion on 12 January 2019 produced an ash plume that reached 800 m above the crater and dispersed to the S (figure 15). A report released for this event by Sutopo at BNPB said that Ibu had erupted almost every day over the past three months; an example given was of activity on 10 January consisting of 80 explosions. There were four MODVOLC thermal alerts through the month.

Figure 15. An eruption at Ibu at 1712 on 21 January 2019 produced an ash plume that rose to 800 m above the crater. Courtesy of BNPB (color adjusted).

Throughout February explosions frequently produced ash plumes as high as 800 m above the crater, and nine MODVOLC thermal alerts were issued. Daily reports showed variable plume heights of 200-800 m most days throughout the month. Wind directions varied and dispersed the plumes in all directions. A VONA released at 1850 on 6 February reported an ash plume that rose to 1,925 m altitude (around 600 m above the summit) and dispersed S. Activity continued through March with the Darwin VAAC and PVMBG reporting explosions producing ash plumes to heights of 200-800 m above the crater and dispersing in various directions. There were ten MODVOLC alerts through the month.

Similar activity continued through April, May, and June, with ash plumes reaching 200-800 m above the crater. There were 12, 6, and 15 MODVOLC Alerts in April, May, and June, respectively.

Planet Scope satellite images show activity at a two vents near the center of the crater that were producing small lava flows from February through June (figure 16). Thermal anomalies were frequent during December 2018 through June 2019 across MODVOLC, MIROVA, and Sentinel-2 infrared data (figures 17 and 18). Sentinel-2 data showed minor variation in the location of thermal anomalies within the crater, possibly indicating lava flow activity, and MIROVA data showed relatively constant activity with a few reductions in thermal activity during January and February.

Figure 16. Planet Scope natural color satellite images showing activity in the Ibu crater during January through June 2019, with white arrows indicating sites of activity. One vent is visible in the 21 February image, and a 330-m-long (from the far side of the vent) lava flow with flow ridges had developed by 24 March. A second vent was active by 12 May with a new lava flow reaching a maximum length of 520 m. Activity was centered back at the previous vent by 23-27 June. Natural color Planet Scope Imagery, copyright 2019 Planet Labs, Inc.

Figure 17. Examples of thermal activity in the Ibu crater during January through May 2019. These Sentinel-2 satellite images show variations in hot areas in the crater due to a vent producing a small lava flow. Sentinel-2 false color (urban) images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Figure 18. MIROVA log radiative power plot of MODIS thermal infrared at Ibu from September 2018 through June 2019. The registered energy was relatively stable through December, with breaks in January and February. Regular thermal anomalies continued with slight variation through to the end of June. Courtesy of MIROVA.

Geologic Background. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/).

The Ebeko volcano, located on the northern end of the Paramushir Island in the Kuril Islands, consists of many craters, lakes, and thermal features and has been frequently erupting since late February 2017. Typical activity includes ash plumes, explosive eruptions, and gas-and-steam activity. The previous report through November 2018 (BGVN 43:12) described frequent ash explosions that sometimes caused ashfall in Severo-Kurilsk (7 km E). The primary source of information is the Kamchatka Volcanic Eruptions Response Team (KVERT). This report updates the volcanic activity at Ebeko for December 2018 through May 2019.

Frequent moderate explosive activity continued after November 2018. Volcanologists in Severo-Kurilsk observed explosions sending up ash, which drifted N, NE, and E, resulting in ash falls on Severo-Kurilsk on 28 different days between December 2018 and March 2019. On 25 December 2018 an explosion sent ash up to a maximum altitude of 4.5 km and then drifted N for about 5 km. Explosions occurring on 8-10 March 2019 sent ash up to an altitude of 4 km, resulting in ashfall on Severo-Kurilsk on 9-10 March 2019. An ash plume from these explosions rose to a height of 2.5 km and drifted to a maximum distance of 30 km ENE.

Satellite data analyzed by KVERT registered 12 thermal anomalies from December 2018 through May 2019. According to satellite data analyzed by MIROVA (Middle InfraRed Observation of Volcanic Activity), only one thermal anomaly was recorded from December 2018-May 2019, and no hotspot pixels were recognized using satellite thermal data from the MODVOLC algorithm.

Geologic Background. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).

Klyuchevskoy has had alternating eruptive and less active periods since August 2015. Activity has included lava flows, a growing cinder cone, thermal anomalies, gas-and-steam plumes, and ash explosions. Though some eruptions occur near the summit crater, major explosive and effusive eruptions have also occurred from flank craters (BGVN 42:04 and 43:05). Intermittent moderate gas-and-steam and ash emissions were previously reported from mid-February to mid-August 2018. The Kamchatka Volcanic Eruptions Response Team (KVERT) is the primary source of information for this September 2018-June 2019 reporting period.

KVERT reported that moderate gas-and-steam activity, some of which contained a small amount of ash, and weak thermal anomalies occurred intermittently from the beginning of September 2018 through mid-April 2019. On 21-22 April 2019 webcam data showed a gas-and-steam plume extending about 160 km SE (figure 31). Moderate Strombolian-type volcanism began late April 2019 and continued intermittently through June 2019. On 11-12 June webcam data showed explosions that sent ash up to a maximum altitude of 6 km, with the resulting ash plume extending about 200 km WNW.

Figure 31. Gas-and-steam plume containing some amount of ash rising from the summit of Klyuchevskoy on 22 April 2019. Photo by A. Klimova, courtesy of Institute of Volcanology and Seismology (IVS FEB RAS).

Thermal anomalies were noted by KVERT during two days in September 2018, six days in April 2019, eleven days in May 2019, and six days in June 2019. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed infrequent weak thermal anomalies December 2018 through early May 2019.

Geologic Background. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

The submarine Axial Seamount volcano is located about 470 km offshore of the Oregon coast. An eruption inferred to have started at 2230 on 23 April 2015 with an earthquake swarm (BGVN 40:03) was confirmed during a 14-29 August 2015 research cruise by the R/V Thompson. According to a personal communication on 23 June 2015 from Bill Chadwick (Oregon State University and NOAA), the length of the eruption is unknown, but it was "very likely days to weeks since the deflation lasted for about 10 days and the temperature signals lasted about a month."

The research cruise revealed new lava flows observed from bathymetric data and observations made during a remotely operated underwater vehicle ROV Jason dive. This eruption "produced the largest volume of erupted lava since monitoring and mapping began in the mid-1980's" (Chadwick and others, 2016). Two large lava flows from the N rift zone (8-16 km N of the summit caldera) were at most 127 m thick; some of the thicker areas had drained collapse features indicating molten interiors when emplaced. The ROV traversed the flows for about 2 km. New, thinner lava flows (figure 13) were also identified in the NE summit caldera and on the NE rim.

Figure 13. Collecting a fragment of lava from the 2015 eruption of Axial Seamount with an arm of the AUV. Credit: Monterey Bay Aquarium Research Institute (MBARI); from Phys.org (2016).

Three recently published papers, Chadwick and others (2016), Nooner and Chadwick (2016), and Wilcock and others (2016), detail the results of eruptive activity in 1998, 2011, and 2015, based on new data from a research cruise conducted after the 2015 eruption (figures 14 and 15). Scientists from the Monterey Bay Aquarium Research Institute (MBARI) issued a new seafloor map (figure 16) of the area of Axial north of the one shown in figure 14, based on underwater surveys conducted in August 2016, uncovering a number of previously undocumented flows from the 2015 eruption (Phys.org, 2016). MBARI ran identical sets of autonomous underwater vehicles (AUV) survey lines across the entire Axial caldera in 2011, 2014, 2015, and 2016, and during the 2016 survey the AUV collected seafloor samples (figure 13).

Figure 14. Map of the summit caldera of Axial Seamount. Locations of mobile pressure recorders (MPR) benchmarks (white circles) and bottom pressure recorders (BPR) instruments (red and blue circles) are indicated. Numbers show vertical displacements in centimeters at each of the MPR benchmarks between 14 September 2013 and 25 August 2015, a period that included pre-eruption inflation, co-eruption deflation, and post-eruption inflation. Numbers in parentheses show subsidence in centimeters during deflation only, as measured by the BPRs. BPRs on the Ocean Observatories Initiative (OOI) Cabled Array (red dots) include tiltmeters. The map also shows locations of 2015 lava flows and eruptive fissures (white outlines and red lines, respectively) and 2011 lava flows and eruptive fissures (gray outlines and yellow lines, respectively). From Nooner and Chadwick (2016).

Figure 15. Map of 2015 lava flows (black outlines) and new fissures (red lines) in the summit caldera of Axila Seamount and on the north rift zone. Also shown are 2011 lava flows (gray outlines) and eruptive fissures (yellow lines) on the south rift zone. Lava samples collected by ROV are shown by dots, colored according to their MgO content. Dashed white outline indicates a magma reservoir from multichannel seismic results, with a dotted white line separating zones of high melt (south) from crystal mush (north). Canadian American Seamount (CASM) vent field and implanted benchmark AX-101 are labeled. From Chadwick and others (2016).

Figure 16. Part of the new map of Axial Seamount produced by MBARI researchers. Black outlines show lava flows from 2015 eruption. From Phys.org (2016).

According to Wilcock and others (2016), the earthquake rates increases from less than 500 per day to as many as about 2000 per day prior to the eruption on 24 April 2015, then decreased rapidly over the next month following the seismic crisis to a background level of 20 per day. During the eruption there were 600 earthquakes measured every hour, and the seafloor at Axial dropped suddenly by about 2.4 m.

Precise pressure sensors measure vertical movements of the seafloor that take place as the volcano gradually inflates (see figure 14). Deformation of the Axial volcano seafloor as measured by pressure sensors (figure 17) indicated gradual inflation followed by rapid deflation during the three most recent eruptions in 1998, 2011, and 2015.

Figure 17. Deformation time series at the Axial Seamount caldera center, showing change in seafloor elevation as a function of time from 1998 to about May 2016. Long-term time series of inflation and deflation at the center of the caldera to 19 May 2016. Purple open dots represent mobile pressure recorder measurements (error bars indicate 1 SD); blue curves show bottom pressure recorder data (drift-corrected after 2000). The relative depth of data before and after the 1998–2000 gap in measurements is unknown. From Nooner and Chadwick (2016).

References: Chadwick, W.W., Jr., Paduan, J.B., Clague, D.A., Dreyer, B.M., Merle, S.G., Bobbitt, A.M., Caress, D.W., Philip, B.T., Kelley, D.S., and Nooner, S.L., 2016 (15 December), Voluminous eruption from a zoned magma body after an increase in supply rate at Axial Seamount, Geophysical Research Letters, v. 43, issue 23, pp. 12,063-12,070; DOI: 10.1002/2016GL071327.

Nooner, S.L., and Chadwick, W.W., Jr., 2016 (16 December), Inflation-predictable behavior and co-eruption deformation at Axial Seamount, Science, v. 354, issue 6318, pp. 1399-1403; DOI: 10.1126/science.aah4666.

Phys.org, 2016 (15 Dec), MBARI's seafloor maps provide new information about 2015 eruption at Axial Seamount (URL: https://phys.org/news/2016-12-mbari-seafloor-eruption-axial-seamount.html).

Wilcock, W.S.D., Tolstoy, M., Waldhauser, F., Garcia, C., Tan, Y.J., Bohnenstiehl, D.R., Caplan-Auerbach, J., Dziak, R.P., Arnulf, A.F., and Mann, M.E., 2016 (16 Dec), Seismic constraints on caldera dynamics from the 2015 Axial Seamount eruption, Science, v. 354, issue 6318, pp. 1395-1399; DOI: 10.1126/science.aah5563.

Geologic Background. Axial Seamount rises 700 m above the mean level of the central Juan de Fuca Ridge crest about 480 km W of Cannon Beach, Oregon, to within about 1400 m of the sea surface. It is the most magmatically robust and seismically active site on the Juan de Fuca Ridge between the Blanco Fracture Zone and the Cobb offset. The summit is marked by an unusual rectangular-shaped caldera (3 x 8 km) that lies between two rift zones and is estimated to have formed about 31,000 years ago. The caldera is breached to the SE and is defined on three sides by boundary faults of up to 150 m relief. Hydrothermal vents with biological communities are located near the caldera fault and along the rift zones. Hydrothermal venting was discovered north of the caldera in 1983. Detailed mapping and sampling efforts have identified more than 50 lava flows emplaced since about 410 CE (Clague et al., 2013). Eruptions producing fissure-fed lava flows that buried previously installed seafloor instrumentation were detected seismically and geodetically in 1998 and 2011, and confirmed shortly after each eruption during submersible dives.

Information Contacts: William Chadwick, Cooperative Institute for Marine Resources Studies (CIMRS), Oregon State University, and NOAA/PMEL Earth-Ocean Interactions Program, Hatfield Marine Science Center, 2115 S.E. OSU Dr., Newport, OR 97365, USA (URL: http://www.pmel.noaa.gov/eoi/).

The eruptive activity at Barren Island that began in October 2013 continued through at least mid-June 2014 (BGVN 39:07). Another eruptive cycle began in March 2015 and continued through 28 February 2016, based on MODIS/MODVOLC thermal anomalies. However, MIROVA hotspots were regular through mid-May 2016, and then sporadic throughout the rest of 2016. The next clear episode began on 15 January 2017 and continued through at least February 2017. Scientists aboard a research ship observed explosions, fire fountains, and lava flows in January 2017.

Activity during October 2013-June 2014. Evidence of renewed activity in the form of lava flows was seen in MODVOLC thermal anomaly data beginning on 12 October 2013. Thermal alert pixels were frequent through 12 February 2014, followed by single anomalies on 12 March and 20 April 2014. Ash plumes were also observed during January-April 2014. Thermal infrared MODIS data processed by the MIROVA system revealed frequent anomalies in April through early May 2014, and in late May to early June; another anomaly was seen in mid-June 2014.

Activity during July 2014-June 2015. No thermal anomalies were seen in MIROVA data for at least five weeks (figure 24), between early June and late July 2014, and then continuing intermittently through the first half of March 2015. The only reported plumes during this time were in the week of 3-9 September 2014 and 22-28 April 2015, but in each case as could not be identified in satellite imagery.

Figure 24. Thermal anomaly MIROVA radiative power data from Barren Island during 7 June 2014-6 June 2015. A weak mid-June 2014 anomaly is followed by intermittent weak activity during late July 2014 through mid-March 2015. A strong period of thermal anomalies in March and April 2015 decreased in intensity but continued into early June 2015. Courtesy of MIROVA.

A strong thermal signature resumed on 17 March 2015 (figure 24) and continued for about three weeks before decreasing in intensity. Lower-level thermal activity continued through the first half of June. Thermal anomalies seen in MODVOLC data also resumed on 17 March, and were frequent through 12 June. Eruptions of ash were observed during 5-7 and 12-13 June 2015, with plumes rising to an altitude of 2-3 km and drifting up to 55 km downwind (table 5).

Table 5. Ash plumes at Barren Island, June 2015-February 2016. Legend: Satellite=analysis of satellite images, wind=wind data. Data provided by the Darwin Volcanic Ash Advisory Centre.

Activity during July 2015-May 2016. Thermal activity paused again for approximately a month in the second half of June and first half of July 2015. Regular thermal anomalies in MODVOLC data stopped after 12 June and resumed on 16 July. Episodic clusters of anomalies with gaps of 1-3 weeks continued until 28 February 2016. Although MODVOLC data did not show thermal anomalies after February 2016, MIROVA data showed ongoing activity until approximately 17 May (figure 25).

A few ash plumes were seen during this period, on 19 August, 22 September, and 8-9 October 2015 (table 5). There were no reported plumes in November or December 2015, but were seen once again in January and February 2016. Plumes typically rose to an altitude of 1.5-2 km and drifted 45-100 km downwind; the longest plume extended 1665 km SW.

Figure 25. Thermal anomaly MIROVA log radiative power data from Barren Island during 21 February 2016-20 February 2017. Regular activity is evident from late February through mid-May 2016. After a gap of about two months, there are only infrequent anomalies through mid-January 2017, after which another episode of frequent anomalies began. Courtesy of MIROVA.

Activity during June 2016-February 2017. Eruptive activity apparently stopped around 16-17 May 2016 for at least seven weeks. MODIS thermal data captured by MIROVA showed a few anomalies (less than 20) from the second half of July through the first half of December 2016 (figure 25). Considering the remote location and rare direct observations at this island volcano, it is possible that the anomalies represent intermittent lava emissions. Regular thermal anomalies were recorded by both MIROVA and MODVOLC beginning on 15 January that were continuing at the end of February 2017.

The National Institute of Oceanography (NIO), part of the Indian Council of Scientific and Industrial Research (CSIR), reported activity on 23 January 2017. Scientists aboard a research vessel were collecting sea floor samples when they observed a sudden ash emission. The team moved closer, about 1.6 km from the volcano, and noted small eruptive episodes lasting 5-10 minutes. Ash emissions were visible in the daytime, and lava fountains feeding lava flows on the flanks were visible at night. The team revisited the volcano on 26 January and observed similar activity over four hours. They sampled sediments and water in the vicinity of the eruption and recovered volcanic ejecta.

Geologic Background. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Information Contacts: Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); The National Institute of Oceanography (NIO), Council of Scientific and Industrial Research (CSIR), New Delhi, India (URL: http://www.nio.org/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

Intermittent weak explosions at Gamalama resulting in ash plumes have occurred for many decades, most recently in September 2012, December 2014, and July-September 2015 (BGVN 40:12). This report covers activity between 1 December 2015 and February 2017. Data were primarily drawn from reports issued by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Center for Volcanology and Geological Hazard Mitigation) and the Darwin Volcanic Ash Advisory Centre (VAAC).

During 1 January-6 March 2016, PVMBG noted that seismicity fluctuated but decreased overall; shallow volcanic earthquakes and signals indicating emissions appeared on 3 March and a series of deep volcanic earthquakes were detected on 6 March. The Alert Level remained at 2 (on a scale of 1-4), and visitors and residents were warned not to approach the crater within a 1.5-km radius.

PVMBG reported that, at 0628 on 3 August 2016, a weak explosion generated an ash plume that rose 500-600 m above the crater and drifted SE and S. Ash emissions decreased at 0655. Consistent with this, the Darwin VAAC, based on analyses of satellite imagery and wind model data, and information from PVMBG, reported that ash plumes reached a maximum altitude of 2.7 km (summit elevation is 1.7 km) and drifted S, SE, E, and NE. Ashfall was reported in areas on the SSE flank, including the Ake Huda area.

A news account (Jakarta Globe) stated that the Babullah Airport in Ternate, North Maluku, was closed for a day while volcanic ash was cleared from the runway (about 6 km ENE of the volcano). On 5 August PVMBG noted that seismicity continued to be elevated, although inclement weather prevented visual observations.

Geologic Background. Gamalama is a near-conical stratovolcano that comprises the entire island of Ternate off the western coast of Halmahera, and is one of Indonesia's most active volcanoes. The island was a major regional center in the Portuguese and Dutch spice trade for several centuries, which contributed to the thorough documentation of Gamalama's historical activity. Three cones, progressively younger to the north, form the summit. Several maars and vents define a rift zone, parallel to the Halmahera island arc, that cuts the volcano. Eruptions, recorded frequently since the 16th century, typically originated from the summit craters, although flank eruptions have occurred in 1763, 1770, 1775, and 1962-63.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Jakarta Globe (URL: http://jakartaglobe.id/).

The submarine Kavachi volcano in the Solomon Islands south of Gatokae and Vangunu islands is frequently active but rarely observed. Consistent activity was reported for more than 4 years between November 1999 and August 2003. An 8-month period of quiet was broken with another explosive eruption above the ocean surface on 15 March 2004 (BGVN 30:03). No observations of ongoing activity are known over the next two years, though eruptions may have continued. Satellite imagery using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) during 2006-2016 frequently revealed evidence of activity, on at least 35 days, using the Visible Near Infrared (VNIR) bands. Very little ASTER imagery is available for Kavachi during 2001-2005.

ASTER images on 27 February and 24 March 2006 (figure 13) show renewed activity. Vigorous upwelling along with turbulent ash-laden water and a sulfur odor was witnessed on 6 April 2007 (BGVN 32:07). An ASTER image on 15 June 2007 (figure 14) showed pulses of discolored water originating from the vent, confirming ongoing activity. A small area of discolored water was next seen in satellite imagery on 12 December 2007. A small plume of discolored water appeared in ASTER imagery again on 26 February 2008. On 20 March 2008 the Landsat 7 Enhanced Thematic Mapper captured an image of an ash-and-steam eruption plume extending about 25 km NNE towards Gatokae (figure 15). The next satellite evidence of discolored water plumes were on 7 October 2008.

Figure 13. ASTER VNIR satellite image showing a submarine plume of discolored water originating above the summit of Kavachi, 24 March 2006. There appears to be turbulence at the ocean surface and a possible line of pumice along the lower left edge of the discolored area. Courtesy NASA/METI/AIST/Japan Spacesystems, and U.S./Japan ASTER Science Team, ASTER via the Image Database for Volcanoes.

Figure 14. ASTER VNIR satellite image showing a submarine plume of discolored water originating above the summit of Kavachi, 15 June 2007. Distinct pulses of activity, possibly individual explosions at the bright surface origin spot, can be identified based on the increasing diffusion of suspended particulates with distance from the source. Courtesy NASA/METI/AIST/Japan Spacesystems, and U.S./Japan ASTER Science Team, ASTER via the Image Database for Volcanoes.

Figure 15. Satellite image showing an eruption plume from Kavachi on 20 March 2008 taken using the Enhanced Thematic Mapper on Landsat 7. Image modified using the "Percent Clip" option. Courtesy of USGS LandsatLook Viewer.

An image on 11 November 2009 showed a larger very bright spot above the summit, possibly indicating turbulent activity at the ocean surface. Evidence of activity became more frequent in 2010, with imagery showing plumes on 15 February, 19 March, 23 June, 11 September, and 30 November. Submarine plumes continued to be visible often in ASTER images the following year, on 1 January, 13 March, 9 May, and 16 October 2011. The next available satellite image with a discolored submarine plume from Kavachi was on 9 April 2012. Additional plumes were seen on 16 April, 3 June (figure 16), 31 August, and 26 November 2012.

Figure 16. ASTER VNIR satellite image showing a submarine plume of discolored water originating above the summit of Kavachi, 3 June 2012. There appears to be a small island or area of persistent ash-laden surface turbulence at the source of the plume. Courtesy NASA/METI/AIST/Japan Spacesystems, and U.S./Japan ASTER Science Team, ASTER via the Image Database for Volcanoes.

Intermittent satellite evidence of ongoing activity continued in 2013 with a discolored water plumes on 28 April, 15 June, 8 July, 25 August, 10 September, and 8 December. On 24 September 2013, Brennan Phillips of the University of Rhode Island passed within 2 km of the main peak onboard the M/Y Alucia but "did not see any visual eruptive activity on the surface."

Although the imagery is not conclusive, many of the ASTER images after 3 June 2012 appeared to show a small island. On 9 January 2014 the ASTER imagery was much clearer, providing greater visual evidence that eruptive activity had built a small island from which discolored water plumes were emanating (figure 17). A few weeks later, on 29 January, the Earth Observing 1 (EO1) Advanced Land Imager (ALI) obtained an image of a submarine plume (BGVN 39:07) and turbulent source area similar to those seen in ASTER imagery. Additional activity was in evidence on 21 March and 8 May.

Figure 17. ASTER VNIR satellite image showing a submarine plume of discolored water originating above the summit of Kavachi, 9 January 2014. A distinct small island or area of persistent ash-laden surface turbulence can be readily identified at the source of the plume. Courtesy NASA/METI/AIST/Japan Spacesystems, and U.S./Japan ASTER Science Team, ASTER via the Image Database for Volcanoes.

A cruise ship operated by EYOS Expeditions reported an eruption "at least four times" on 10 June 2014 (figure 18). The Expeditions' website noted that a staff member "spotted on the horizon discolored water and disturbances on the surface. As the vessel approached closer a few large plumes of water broke the surface about once every 10 minutes. Just before the ship left, however, [the] sea seemed to erupt and a massive plume of water and ash shot high into the air…." The island, or possibly an eruption exhibiting turbulence with abundant ash at the surface, appeared again on a 9 November 2014 image, and submarine plumes were evident in an 11 December 2014 image.

Figure 18. Photo of an eruption sequence from Kavachi on 10 June 2014 taken from a cruise ship. Courtesy of EYOS Expeditions.

An expedition for National Geographic in January 2015 took place during a rare lull in volcanic activity that enabled access to the volcano for mapping and sampling. B. Phillips reported that no eruptive activity was seen while at the summit location on 12-14 and 18 January 2015, but there was a large surface plume and lots of off-gassing from the crater rim; ASTER imagery confirmed a plume of discolored water on 12 January. Autonomous cameras deployed directly into the crater observed sharks, reef fish, and what appear to larvaceans (National Geographic, 2015).

Satellite imagery showed discolored submarine plumes on 18 October 2015, but then not again until 26 August 2016. Eruptions were witnessed on a second visit by B. Phillips for National Geographic during 31 October-1 November 2016 (see National Geographic, 2017). Activity consisted of phreato-magmatic explosions approximately every 7 minutes that sent steam, ash, and incandescent tephra up to 50 m above the ocean surface. There was an occasional larger eruption roughly every hour. A remotely operated surface "drone" with a GoPro camera was right at the edge of the explosion but remained functional. Small lava particles stuck to the PVC hull of the vehicle itself were recovered and given to the Marine Geological Samples Laboratory (MGSL) of the Graduate School of Oceanography (GSO), University of Rhode Island."

Bathymetric survey. A paper by Phillips and others (2016) following the January 2015 visit included medium-resolution bathymetry of the main peak (figure 19), along with benthic imagery, biological observations, petrological and geochemical analysis of samples from the crater rim, measurement of water temperature and gas flux over the summit, and descriptions of the hydrothermal plume structure. Based on the bathymetry, the summit was described by Phillips and others (2016) as being oblong with a pockmarked crater measuring approximately 75 x 120 m, and a rim rising to an average of 24 m depth. The deepest soundings on the peak were about 70 m and indicated asymmetrical terrain surrounded by almost uniform flanks with 18° slopes that descend to depths greater than 1,000 m. They confirmed the existence of a "southwest extension," or secondary summit rising to 260 m depth 1.3 km SW of the main summit.

Figure 19. Bathymetry of Kavachi submarine volcano and the summit crater (inset, lower right). Red circles indicate locations of water column profiles and benthic imagery. White diamonds locate baited drop cameras deployments. The blue line delineates the path of a surface drifter that measured temperature and atmospheric CO2, The contour map and the inset at lower right were created from approximately 85,000 depth soundings visualized and edited as a three-dimensional point-cloud using IVS Fledermaus. The location map (upper right) was created with Generic Mapping Tools (v 4.5) using data available from Marine Geoscience Data System's Global Multi-Resolution Topography Data Synthesis (v 3.1). From Philips and others (2016).

References: National Geographic, 2015, Sharks discovered inside underwater volcano (exclusive video) (URL: http://video.nationalgeographic.com/video/expedition-raw/150708-sciex-exraw-sharks-underwater-volcano; https://www.youtube.com/watch?v=0e3t18rrjOA).

National Geographic, 2017, Robot vs. Volcano: "Sometimes It's Just Fun to Blow Stuff Up" (exclusive) (URL: http://video.nationalgeographic.com/video/expedition-raw/170419-sciex-exraw-robot-vs-volcano-sometimes-just-fun-to-blow-stuff-up; https://www.youtube.com/watch?v=Ca0zAAIVK3E).

Phillips, B.T., Dunbabin, M., Henning, B., Howell, C., DeCiccio, A., Flinders, A., Kelley, K.A., Scott, J.J., Albert, S., Carey, S., Tsadok, R., and Grinham, A., 2016. Exploring the "Sharkcano": Biogeochemical observations of the Kavachi submarine volcano (Solomon Islands), Oceanography v. 29(4), p. 160-169 (https://doi.org/10.5670/oceanog.2016.85).

Geologic Background. Named for a sea-god of the Gatokae and Vangunu peoples, Kavachi is one of the most active submarine volcanoes in the SW Pacific, located in the Solomon Islands south of Vangunu Island about 30 km N of the site of subduction of the Indo-Australian plate beneath the Pacific plate. Sometimes referred to as Rejo te Kvachi ("Kavachi's Oven"), this shallow submarine basaltic-to-andesitic volcano has produced ephemeral islands up to 1 km long many times since its first recorded eruption during 1939. Residents of the nearby islands of Vanguna and Nggatokae (Gatokae) reported "fire on the water" prior to 1939, a possible reference to earlier eruptions. The roughly conical edifice rises from water depths of 1.1-1.2 km on the north and greater depths to the SE. Frequent shallow submarine and occasional subaerial eruptions produce phreatomagmatic explosions that eject steam, ash, and incandescent bombs. On a number of occasions lava flows were observed on the ephemeral islands.

Information Contacts: EYOS Expeditions, Knox House, 16-18 Finch Rd, Douglas, Isle of Man, IM1 2PT (URL: http://www.eyos-expeditions.com/2014/07/kavachi-volcano/, https://my.yb.tl/eyosexpeditions/1604/); Brennan Phillips, Harvard University, Wyss Institute for Biologically Inspired Engineering, Wood Lab, 60 Oxford St., Cambridge, MA 02138 USA; Image Database for Volcanoes, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST) (URL: https://gbank.gsj.jp/vsidb/image/index-E.html, https://gbank.gsj.jp/vsidb/image/Kavachi/aster_p1.html); USGS LandsatLook Viewer (URL: https://landsatlook.usgs.gov/).

Intermittent ash explosions during the last century have characterized activity at Japan's Kuchinoerabujima volcano, located at the northern end of the Ryukyu Islands approximately 260 km S of Nagasaki, Japan. Brief periods of higher seismicity had been detected in the last approximately 30 years, although no explosions had been recorded since 1980 (BGVN 35:11 and 38:01). A new explosion occurred on 3 August 2014, and activity remained elevated through June 2015. Information on the latest activity is provided by the Japan Meteorological Agency (JMA) monthly reports and aviation alerts are from the Tokyo Volcanic Ash Advisory Center (VAAC).

A modest explosion from Shindake crater on 3 August 2014 caused JMA to increase the Alert Level at the volcano. Activity decreased shortly after the explosion, and only steam plumes, fumarolic activity, and occasional incandescence were observed for the next nine months. A large explosion on 29 May 2015 generated a gray-black ash plume that rose to over 9 km altitude and sent pyroclastic flows down the flanks; JMA increased the Alert Level and ordered evacuation of local residents. Activity declined after a few days, and Shindake remained quiet until a smaller explosion on 18 June 2015. The ash plume did not exceed 1 km, but ashfall was reported in towns on neighboring islands and in areas up to 80 km E. Two additional smaller explosions were reported on 18 and 19 June. Seismicity decreased significantly after the 19 June explosion, but SO₂ emissions remained elevated until October 2015. The JMA did not lower the Alert Level until June 2016.

Activity during August 2014-February 2015. JMA reported an eruption from the vicinity of Shindake crater around noon local time on 3 August 2014, with a gray plume rising more than 800 m above the crater rim. This led to an increase in the Alert Level from 1 (Normal) to 3 (Do not approach the volcano) on a 5-level scale. An overflight confirmed traces of ash on the W flank. The Tokyo VAAC reported that the plume rose to an altitude greater than 1.5 km and drifted N. On 5 August, seismicity decreased, and views from a remote web camera showed a white plume rising 50 m above the crater rim. For the rest of August, seismicity remained low and steam plumes rose 50 to 800 m above the crater.

During September 2014, white plumes were generally observed 200-800 m above the crater when visibility was not obscured by weather; seismicity remained low. Scientists conducting a field survey on 12 September found SO₂ emissions at 300 metric tons per day (t/d), higher than the background value of 60 t/d measured on 21 May 2014. Occasional earthquakes were recorded in October 2014, and the volume of gas emissions remained relatively high compared with before the August eruption; steam-and-gas plumes rose to 600 m above the crater rim. During field surveys on 7 and 8 October scientists measured SO₂ emissions of 500 t/d. Gas emissions rose from within the Shindake crater, around a thermally anomalous fissure at the W edge of the crater, as well as from a new fumarole on the SW flank of the crater. In November, plumes continued to rise as high as 1,000 m above the crater. In another survey on 9 December 2014, scientists found that SO₂ levels had increased to 1,700 t/d.

Emissions of SO₂ remained high during the second half of January 2015, ranging from 1,100 to 3,100 t/d. A M 2.2 seismic event located 5 km beneath the island was recorded on 24 January. Observations made during field surveys in February confirmed continued steam emissions, and thermal anomalies from the W crater rim fissure and the new fissure on the SW flank. SO₂ emissions decreased slightly from January levels to a range of 400 to 2,700 t/d in February, and steam plumes continued to rise 400-700 m above the crater.

Activity during March-June 2015. Incandescence at night was first recorded at the Shindake Crater from 24 to 31 March 2015 with a high-sensitivity camera. Aerial observation on 25 March by JMA and JCG (Japan Coast Guard) indicated a temperature rise and continued fumarolic activity around the thermal anomaly W of the crater rim. SO₂ emissions remained high in March (1,000 to 3,700 t/d) and April (900 to 2,600 t/d), and steam plumes rose to 1 km above the crater. Incandescence was occasionally observed at night during April and again during 18-22 May; fumarolic activity continued along with a rise in temperature at the W and SW fissures. Steam plumes were observed rising to 600 m above the crater in May.

According to JMA, at 0959 local time on 29 May 2015, a large explosive phreatomagmatic eruption generated a gray-black ash plume that rose to over 9 km altitude and drifted ESE (figure 5). The plume was reported by the Tokyo VAAC to be at 10.9 km altitude about an hour after the eruption. The largest of several pyroclastic flows descended NW from the SW side of the crater in the Mukaehama district and reached the coast. Based on these events, JMA raised the Volcanic Alert Level to 5 (Evacuate). Aerial observation conducted on the same day (in collaboration with the Kyushu Regional Bureau of the Ministry of Land, Infrastructure, Transport and Tourism) revealed additional pyroclastic flows moving in nearly all directions from the Shindake crater (figure 6) including flows reaching halfway down the mountain to the SW and SE of the crater. Seismicity increased immediately after the eruption, but had decreased by midday.

Figure 5. Ash plume from Kuchinoerabujima's Shindake Crater during an explosion on 29 May 2015. The plume height was reported by the Tokyo VAAC as 10.9 km altitude. Photo taken from the neighboring island of Yakushima by Itaru Takaku. Courtesy of Kyodo News and The Japan Times.

Figure 6. Google Earth imagery dated 5 June 2015, one week after a large explosion which generated several pyroclastic flows around the summit crater at Kuchinoerabujima. Note the brown areas extending in most directions away from the summit crater (beneath the white clouds), all the way to the coast on the NW and W flanks that are the result of the pyroclastic flows that occurred on 29 May 2015. Courtesy of Google Earth.

According to a news article (The Japan Times), all residents and visitors (141 people) were safely evacuated by a ferry, coast guard ship, and helicopter to neighboring Yakushima Island (25 km SE). A resident of Yakushima reported that ash reached the island. Later that day, ash plumes rose 200 m and drifted SW.

Ash plumes continued the next day, 30 May, rising only 1.2 km. A field team observed discolored trees on the SE and SW flanks, and fallen trees near the coast on the NW flank. Cloud cover prevented views of the eruption area, but the team was able to confirm continued fumarolic activity and incandescence in the W part of the crater. Seismicity continued at low levels, and during the first week of June white plumes rose 100-400 m above the crater rim.

Another smaller eruption on 18 June 2015 caused lapilli and ash to fall on the E side of the island. Ash was reported in Yakushima Town (44 km ESE on Yakushima Island), Nishinoomote City (80 km NE on Tanegashima Island), and Nakatane Town (72 km E on Tanegashima). Small eruptions also occurred at 1631 on 18 June and at 0943 on 19 June. Tokyo VAAC reported the larger 18 June eruption, but plume heights were below 1 km, and not observed on satellite. Aerial observations on 20 June by JMA revealed no traces of new pyroclastic-flow deposits around the crater or on the flanks.

Post-eruption observations through June 2016. Emissions of SO₂ remained elevated during June 2015 (800-1,700 t/d), and decreased somewhat in July to 500-700 t/d. They decreased further to 200-300 t/d in August. Increased seismicity was recorded briefly from 1-3 and 6-11 August. SO₂ emissions continued to decline in September, except for a spike of 700 t/d on 10 September. Thermal infrared observations taken during a field survey in October 2015 indicated a decrease in temperature around the fissure W of the crater rim since the 29 May eruption. Emissions of SO₂ remained below 300 t/d for the remainder of 2015 and no further activity was reported, although the Alert Level remained at 5. On 14 June 2016, JMA lowered the Alert Level to 3; seismic activity and SO₂ flux values were below levels detected prior to the May-June 2015 eruption.

Geologic Background. A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km W of Yakushima. The Furudake, Shindake, and Noikeyama cones were erupted from south to north, respectively, forming a composite cone with multiple craters. The youngest cone, centrally-located Shindake, formed after the NW side of Furudake was breached by an explosion. All historical eruptions have occurred from Shindake, although a lava flow from the S flank of Furudake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shindake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Google Earth (URL: https://www.google.com/earth/); The Japan Times (URL: http://www.japantimes.co.jp/news/2015/05/29/national/volcano-erupts-isle-kagoshima-prompting-evacuation-order/).

The remote island of Manam, 13 km off the northern coast of mainland Papua New Guinea is a basaltic-andesitic stratovolcano that has a 400-year history of recorded evidence for recurring low-level ash plumes and occasional Strombolian emissions, lava flows, pyroclastic avalanches, and large ash plumes. Pyroclastic flows and Strombolian activity during much of 2012 and 2013 were accompanied by numerous ash plumes rising a few kilometers above the summit (BGVN 38:06, 39:08). Activity between January 2014 and January 2017, described below, includes persistent thermal anomalies during most of this time, and a major ash plume rising to nearly 20 km altitude on 31 July 2015.

Monitoring is done by Papua New Guinea's Rabaul Volcano Observatory (RVO), part of the Department of Mineral Policy and Geohazards Management (DMPGM). This information is supplemented with aviation alerts from the Darwin Volcanic Ash Advisory Center (VAAC). MODIS thermal anomaly satellite data is recorded by the University of Hawai'i's MODVOLC thermal alert recording system, and the Italian MIROVA system.

MIROVA thermal anomaly data suggests Manam was intermittently active from at least late June 2014 through the end of the year. A single ash plume was reported on 6 September and two more were observed on 21 and 22 December. The appearance of MODVOLC thermal anomalies in late January 2015 that grew more frequent through April indicated increasing activity along with sporadic low-level ash plumes in late February and late April. Persistent levels of thermal anomalies and ash plume reports continued in May through early July.

On 31 July 2015 at about 1130 local time a large explosion sent an ash plume to nearly 20 km altitude, spreading volcanic blocks and ash over a wide area, and injuring two people. A second substantial ash plume rose to 6.4 km on 8 August. This was followed by three more small plumes in August, one in September, and two in October 2015 (on 8 and 29) before the volcano quieted down for a few months.

Thermal anomalies were present at the end of January 2016, and an ash plume was observed on 4 March 2016. New thermal anomalies intensified until June and then tapered off in early July. Persistent but more intermittent thermal anomalies continued throughout the year and were ongoing as of early January 2017.

Activity during 2014. Numerous explosions during 2013 tapered off at the end of the year, with the last ash emissions reported on 15 December 2013. In January 2014, RSAM values were lower but still fluctuating above background levels. A report from RVO in early April noted that both summit craters remained quiet through March 2014, with no audible noises or incandescence visible at night. The seismicity remained within background levels of 160-180 RSAM and daily volcanic event counts ranged from 830 to 920. Tiltmeter data showed no significant short-term changes, but over the previous three months there was a gradual inflationary trend towards the summit area. The Alert Level was lowered to Stage 1.

A thermal anomaly appears at the very end of June 2014 in the first available MIROVA LRP data (figure 30). This is followed by additional thermal anomalies in August, October, and November. The Darwin VAAC reported a small ash plume on 6 September 2014 that rose to 2.1 km altitude (300 m above the summit) and drifted 37 km NW. It was visible on infrared satellite imagery for a few hours before dissipating. In their report for October 2014, RVO noted that Manam remained quiet for the month with no audible noises or incandescence; seismicity remained at low to moderate levels, and daily volcanic-event counts ranged between 860 and 920. They also observed that the long-term inflationary trend at the summit observed since the beginning of 2014 continued. Small amounts of white-gray ash drifting SE were reported by RVO on 21 and 22 December from the Southern Crater, with a plume height of only 200 m. They also noted continued E-W inflation.

Figure 30. MIROVA Log VRP data for Manam from 22 June 2014 through 22 June 2015. Intermittent thermal anomalies are recorded at the end of June, early and late August, early October, and mid-November 2014. Thermal activity increased in frequency and intensity starting in the second half of January 2015. Courtesy of MIROVA.

Activity during 2015. RVO noted incandescence from the Main Crater beginning on 19 January 2015, growing stronger during the last week of the month, matching observations in the MIROVA data (figure 30). A MODVOLC thermal alert pixel appeared on 23 January. Seismicity also changed after the middle of the month when RSAM values rose above 200 on 16 January and went as high as 500 on 31 January, after which they declined rapidly and remained low during February.

In February 2015, seismicity was characterized by small to moderate sub-continuous and continuous volcanic tremors. Increased incandescence was also evident from the Main Crater during February. RVO reported weak-to-bright steady incandescence during 7-10, 21, and 26 February. MODVOLC captured two thermal alert pixels on 8 February, and MIROVA reported an anomaly at the end of the first week and during the last week of the month. An ash plume was observed in satellite data by the Darwin VAAC on 24 February; the plume rose to 3 km altitude (1.2 km above the summit) and drifted 37 km W. RSAM values rising to 500 by 18 March led RVO to raise the Alert Level that day to Stage 2. Visual observations were difficult due to weather during much of the month, but MODVOLC reported thermal alert pixels on 19 and 26 March, and MIROVA captured several anomalies at the beginning of a period of increased frequency and intensity of thermal anomalies that lasted through mid-June (figure 30).

RVO reported that during April 2015 both craters released variable amounts of white vapor. Clearer skies revealed incandescence from the Southern Crater during nine nights of the month and seven times from the Main Crater. This is consistent with satellite thermal anomaly observations by MODVOLC on six different days, with four of them being multiple pixel alerts, and numerous anomalies captured by MIROVA. Two ash eruptions were reported by the Darwin VAAC on 27 and 30 April. The first low-level plume rose to 2.4 km and was observed in satellite imagery extending over 100 km to the W before dissipating on 28 April. The second plume was observed at the same altitude drifting 150 km NW. Seismicity remained high during April, still characterized by discreet small to moderate low-frequency earthquakes, and RSAM values ranged between 300 and 650, increasing during the month. Ground deformation GPS measurements at the end of April confirmed the continuing inflationary trend recorded by the electronic tiltmeters since the last measurements taken in May 2013 (figure 31).

Figure 31. Electronic tilt measurements at Manam between 26 February 2011 and 1 May 2015 show a continuing inflationary trend. Eruptions in August 2012 and January 2013 are shown by red arrows. Courtesy of RVO (Volcano Information Bulletin 01-042015, 4 May 2015).

Multiple sources of satellite data confirmed that Manam was active during May 2015. MODVOLC thermal alert pixels were reported from MODIS data captured on 6 and 22 May; MIROVA thermal anomalies were frequent. Ash plumes were reported from visible satellite imagery by the Darwin VAAC on 13 May at 3 km altitude drifting 37 km NE; SO₂ plumes were captured by NASA's OMI instrument on the Aura satellite on 2, 12, 13, and 20 May (figure 32).

Figure 32. SO2 plumes captured by NASA's OMI instrument on the Aura satellite for Manam during May 2015. Clockwise from top left: 2 May, 12 May, 13 May, and 20 May. Missing data (gray stripes) are due to OMI row anomaly. Courtesy of NASA/GSFC.

During June and early July 2015 there were four series of Volcanic Ash advisory reports from the Darwin VAAC. The first, on 21 and 22 June, reported a 3-km-altitude ash plume that extended over 35 km N and NW. The second, from 28 to 30 June, had altitudes that started at 2.4 and rose to 3 km, and drifted 75 km NE. A third plume emerged late on 30 June and lasted through 1 July, drifting 130 km E at 2.4 km altitude. A fourth plume reported on 2 July was confirmed by RVO as only a steam plume with no ash, and was seen in satellite imagery drifting 45 km E at 2.4 km altitude. A single MODVOLC thermal alert pixel was recorded on 7 July.

RVO reported a significant eruption on 31 July 2015 from the Southern Crater beginning about 1130 local time. They observed that low roaring noises marked the onset of the explosion followed by continuous ejection of scoria until about 1330. Fist-sized volcanic debris was reported at Warisi village on the E side of the island. At Baliau on the N side, clasts were about 10-20 cm in diameter. Two people were reportedly knocked unconscious from the falling scoria. Strong emissions of dark gray ash clouds followed the ejection of scoria and continued into the early afternoon. By 1740 emissions consisted of light gray ash clouds. The news source One Papua New Guinea reported that fine ash began to fall over Bogia (25 km SW on the mainland) around 1245 local time.

The ash plume was initially observed in satellite imagery by the Darwin VAAC at 19.8 km altitude spreading out in all direction for 100 km. It was captured by the Japanese Himawari-8 satellite (figure 33); an animation of the imagery showing the eruption was provided by Miller et al. (2016). Four hours later, the plume was visible 370 km to the SW. A lower-altitude ash plume at 6.7 km was observed the next day extending over 100 km SW. A significant SO₂ plume was partially captured by the Aura instrument on the OMI satellite the next day, and measured an SO₂ mass of 3.206 kilotons.

Figure 33. Ash cloud from Manam captured with True Color imagery by the Himawari-8 satellite on 31 July 2015 at 1150 local time, showing ash dispersing in all directions shortly after the explosion. Data courtesy of JMA (Japan Meteorological Agency), annotated image courtesy of RAMMB/CIRA (in Q4 report for 2015). An animation of the imagery showing the eruption is provided by Miller et al. (2016).

The Darwin VAAC reported a new small ash plume on 6 August 2015 rising to 2.7 km drifting around 40 km to the NW, and another large ash plume on 8 August that initially rose to 6.4 km and drifted SSW. Pilots reported the ash at 5.8 km altitude about 90 km W of Kiunga Airport which is located 475 km SW of Manam. About 24 hours later, pilots reported another ash plume at 6 km altitude 150 km SE of the volcano. A hot spot was observed at the summit on 9 August; two MODVOLC thermal alert pixels appeared that day, and another one appeared on 15 August. A small plume was reported on 21 August, only rising to 2.1 km and drifting about 8 km ESE. This was followed two hours later by an ash plume observed 16 km NW at the same altitude, which continued to drift NW to 75 km before dissipating. Additional ash plumes were reported from 26-28 August rising to 2.4 km and drifting from 35 to 75 km, first NE, then N and NW; a small plume was reported on 31 August at 2.1 km drifting 75 km N before dissipating that day.

A single MODVOLC thermal alert pixel on 4 September was the last recorded in 2015. The next plume on 7 September was small, rising only to 2.1 km and drifting 75 km NW, briefly observed in one satellite before dissipating. It was a month until the next ash plume on 8 October 2015, when Darwin VAAC made a satellite observation of a plume at 1.8 km drifting 45 km NW. The last ash plume of 2015 was captured in satellite images on 29 October between 2.1 and 2.4 km altitude around 35 km NW.

Activity during 2016. The MIROVA data recorded thermal activity on about 29 January 2016 that increased in intensity and frequency in early March (figure 34). A small ash plume on 4 March rose to 3 km altitude and drifted about 90 km SE according to the Darwin VAAC. Increased thermal activity was recorded in MODVOLC thermal alert pixels and MIROVA data from early March through mid-July. There were no reports from the RVO during this time. The first MODVOLC alert was recorded on 7 March and they were persistent, almost every week, through the second week of July. On 13 July, an ash plume was observed by the Darwin VAAC in satellite imagery at 3 km altitude drifting 55 km W for a few hours before dissipating. After that, single-pixel MODVOLC thermal alerts were recorded on 20 September and 6 October. The MIROVA analysis of the MODIS data records a similar picture with a clear increase in the frequency and intensity of anomalies between early March and mid-July (figure 34); continuing pulses of thermal anomalies are present every month into January 2017.

Figure 34. Log Radiative Power from MODIS thermal anomaly data recorded by MIROVA for Manam between 19 January 2016 and 18 January 2017. The increased frequency and intensity of thermal anomalies between early March and mid-July agrees well with other indicators of volcanic activity. Additionally, the MIROVA data suggests continued intermittent activity through 18 January 2017. Courtesy of MIROVA.

Reference: Miller S D, Schmit T L, Seaman C J, Lindsey D T, Gunshor M M, Kohrs R A, Sumida Y, Hillger D, 2016, A Sight for Sore Eyes: The Return of True Color to Geostationary Satellites, Bulletin of the American Meteorological Society, vol. 97, no. 10. DOI: http://dx.doi.org/10.1175/BAMS-D-15-00154.1. Animated imagery of the 31 July 2015 eruption can be viewed at http://journals.ametsoc.org/doi/suppl/10.1175/BAMS-D-15-00154.1/suppl_file/10.1175_BAMS-D-15-00154.2.html .

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/, http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Regional and Mesoscale Meteorology Branch (RAMMB) / Cooperative Institute for Research in the Atmosphere (CIRA), NOAA/NESDIS, Colorado State University, Fort Collins, CO 80523-1375, USA (URL: http://rammb.cira.colostate.edu/); One Papua New Guinea (URL: http://www.onepng.com/2015/07/manam-volcano-erupts.html).

Pavlof volcano, near the end of the Alaska Peninsula 970 km SW of Anchorage, frequently produces explosive eruptions from the summit vents and occasional lava flows. The largest confirmed historical eruption took place in 1911 when a fissure opened on the N flank; it has erupted more than 25 times since then. The last reported eruption in mid-November 2014 included lava fountaining from a vent just N of the summit, and flows of rock debris and ash descending the N flank, along with an ash plume that rose to around 9 km altitude and drifted 300 km NW. Pavlof was quiet in 2015, but then abruptly renewed activity in late March 2016. It is monitored primarily by the Alaska Volcano Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC).

A sudden vigorous eruption that began on 27 March 2016 lasted for about 20 hours, sending ash to 11 km altitude, producing a plume dispersed NE for 1,200 km, and a similarly large SO₂ plume. The volcano was then quiet until a short-lived, smaller ash emission occurred in mid-May for eight days. Intermittent low-level ctivity picked up again from late June through late July 2016, characterized by minor emissions of dark-colored ash and steam rising to 4.5 km altitude. Fallout of ash was limited to the flanks of the volcano and the immediate area around Pavlof. The last report of ash emissions was on 30 July, although low-amplitude tremors and steam plumes persisted through August, and intermittent thermal anomalies from the summit continued through the end of 2016.

After a short and intense eruption between 12 and 15 November 2014 (BGVN 40:04), activity decreased quickly to background levels. The AVO had reduced the Aviation Color Code (ACC) from Red (highest) to Orange on 16 November, and from Orange to Yellow on 25 November. Seismicity remained slightly above background levels until early January. On 15 January 2015 the AVO reduced the ACC to the lowest level of Green where it remained for over a year until it was changed abruptly to Red on 28 March 2016 at the start of a new eruption.

AVO reported that seismicity began to increase at 1553 on 27 March 2016, characterized by a quick onset of continuous tremor. An ash plume rose to an altitude of 6.1 km, and by 1618 was drifting N (figure 13). During the night, lava fountaining from the summit crater was observed by mariners, pilots, and residents of nearby Cold Bay (60 km SW).

Figure 13. Pavlof erupts, sending a plume of volcanic ash into the air on the evening of 27 March 2016 (AKDT) as photographed by a passenger on a plane travelling to Anchorage from Dutch Harbor. Courtesy of Colt Snapp.

On 28 March, tremor levels remained high; lightning in the ash plume was detected in the morning, and infrasound data from a sensor network in Dillingham (470 km NE) indicated sustained ash emissions. At 0700 a continuous ash plume was evident in satellite images drifting more than 650 km NE, and a MODIS image captured at midday revealed the extent and substantial thickness of the cloud (figure 14). A SIGMET (significant meteorological information notice) issued by the National Weather Service (NWS) Alaska Aviation Weather Unit indicated that the maximum ash-cloud altitude was approaching 11 km. Strongly elevated surface temperatures also suggested the presence of lava flows.

Figure 14. The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on a NASA satellite acquired this image of the ash plume from Pavlof at 1145 Alaska time (2145 UTC) on 28 March 2016 extending several hundred km to the NE. Courtesy of NASA Earth Observatory.

The energetic ash-producing phase of the eruption lasted from 1600 AKDT (00:00 UTC) on 27 March until about 1230 AKDT (20:30 UTC) on 28 March, and produced an ash cloud that stretched NE over Bristol Bay and interior Alaska for over 1,200 km. As a result, over 40 Alaska Airlines flights to and from Fairbanks, Alaska, were cancelled according to NBC News. Minor ashfall (0.8 to 6.3 mm or 1/32 to 1/4 in) was reported in the nearby community of Nelson Lagoon (80 km NW) and trace ashfall (less than 0.8 mm) was confirmed near Dillingham (470 km NE). A large SO₂ plume also drifted NE from the volcano extending all the way across Alaska to Yukon Territory and British Columbia in Canada (figure 15).

Figure 15. A large SO2 plume trails NE from Pavlof on 28 March 2016 after a substantial explosion sent an ash plume to nearly 12 km altitude. The ash cloud and the SO2 plume both extended for 1,200 km NE across interior Alaska. Courtesy of NASA/GSFC.

Seismicity and infrasound signals had decreased to low enough levels by 1230 on 28 March that the AVO lowered the Aviation Color Code to Orange and the Volcano Alert Level to Watch. However, seismic tremor remained above background levels. Ash emissions decreased through the night and were barely visible in a satellite image acquired at 0625 AKDT on 29 March. Remnant ash continued to drift over Bristol Bay and areas of interior Alaska. The webcam at Cold Bay recorded intermittent, low-level ash plumes rising as high as 4.6 km.

Thermal anomalies, measured by MODIS satellite sensors and analyzed by MODVOLC, appeared from 28 March (0025 UTC) through 29 March 2016 (1360 UTC), with 20 pixels recorded on 28 March. The MIROVA system also recorded an abrupt spike to 'Very High' thermal anomaly levels on 28 March, dropping slightly in the next two days (figure 16) and then disappearing a few days later. Low-power anomalies were detected on 2 and 6 April, and then ceased for several months.

Figure 16. MIROVA Log Radiative Power data for Pavlof between 28 December 2015 and 28 December 2016. Note the 'Very High' level spike in Log Radiative Power during 28-30 March 2016. Values dropped significantly in early April and then disappeared for several months. Low VRP values reappeared in late August and were intermittent for the remainder of 2016. AVO determined that the summit crater was enlarged as a result of the March 2016 explosion; the new crater geometry possibly allowed satellite sensors to more easily detect emissions of hot gases from the vent. Ongoing observations of moderately elevated surface temperatures between August and December 2016 likely reflect this change in the crater, and do not indicate new eruptive activity or rising magma, according to AVO scientists. Courtesy of MIROVA.

The AVO reported that the intensity of the eruption greatly decreased during 29-30 March, although The Canadian Press reported that ash from the eruption had caused flights in and out of Yellowknife and Regina, Canada, to be cancelled on those dates. Elevated surface temperatures identified in satellite data and visual observations of low-level, intermittent ash plumes were noted during brief breaks in poor weather conditions during these days. Airwave signals, indicative of small explosions at the summit, were recorded on 3 April, but tremors had ceased by the next day. On 6 April AVO noted no signs of ash emissions or lava effusion during the previous week, and seismicity was at low levels. Thermal anomalies at the summit were occasionally visible, though likely indicating cooling processes of previously erupted lava. AVO lowered the Aviation Color Code to Yellow and Volcano Alert Level to Advisory on 6 April. After two more weeks of no activity, the ACC was lowered to Green/Normal on 22 April 2016.

On 13 May 2016 the AVO raised the Aviation Color Code back to Orange as a result of increased seismicity typically associated with minor eruptive activity. Four minor ash eruptive episodes were inferred from seismic data between 13 and 16 May. On 14 May, local observers in Cold Bay reported ash emissions below 5 km in the vicinity of the volcano. According to the Anchorage VAAC, on 15 May a minor eruption was noted on the Cold Bay web camera, but volcanic ash was not visible in satellite data. Elevated surface temperatures were detected in satellite data on 15 May. Periods of elevated volcanic tremor and a small explosion associated with minor ash emissions was noted on 17 May; observers in Cold Bay and Sand Point (90 km E) reported ash emissions interspersed with steam emissions. The Anchorage VAAC noted that strong winds caused resuspension of volcanic ash on the lee side of Pavlof on 17 and 18 May. The AVO lowered the ACC to Yellow on 20 May and noted that all volcanic ash clouds produced during the 13-17 May event were below 4.5 km altitude, and that no lava effusion or fountaining was detected. Weak seismic tremor and small explosions were observed on 21 May, after which activity ceased. The AVO lowered the ACC to Green on 17 June.

Seismic activity increased again on 30 June for about a week, prompting the AVO to raise the ACC to Yellow on 1 July 2016; minor steam emissions were also observed in the web camera. AVO technicians installed a new web camera in the Black Hills area north of the volcano near the Bering Sea coast in early July. On 11 July, weakly elevated surface temperatures were observed at the summit in satellite imagery and a steam and gas cloud extended SW for about 80 km. Minor ash emissions reaching a few tens of meters above the summit were observed that afternoon extending a few kilometers to the SW. Small ash emissions were again observed on 18 July along with an increase in seismic tremor for about 48 hours.

On 28 July a low-intensity eruption with vigorous degassing produced a steam-rich plume and minor ash emissions. As a result, the AVO raised the ACC to Orange. The drifting steam and ash cloud was below 4.6 km above sea level and dissipated rapidly. The Anchorage VAAC reported steam and minor ash emissions continuing through 30 July.

A decline in activity led AVO to lower the ACC to Yellow on 4 August. Periods of low-amplitude tremor continued, but no plumes or thermal signals at the summit were detected. Elevated surface temperatures at the summit were observed in satellite data on 8 August, and a low-level but persistent steam plume was visible in web camera images on 11 August. A large steam plume was noted by observers in Sand Point on 15 August. Elevated surface temperatures were detected through cloud cover in satellite data on 20 and 25 August. Low-level unrest continued through the fall with persistent degassing from the summit and elevated surface temperatures detected in satellite data. A robust steam plume on 31 August reached 4.6 km, but there was no evidence of ash and it dissipated rapidly.

Several times during late September during clear views, webcam images showed a persistent steam plume from the summit crater. Elevated surface temperatures in the summit crater were observed in satellite images on 25, 28, and 29 September, and again during 4-6, 13-14, and 16 October. In early November, the AVO determined that the summit crater was larger and more centrally located than before, as a result of the March 2016 explosion. The new crater geometry possibly allowed satellite sensors to more easily detect emissions of hot gases from the vent. Ongoing observations of moderately elevated surface temperatures (figure 16) likely reflect this change in the crater, and do not indicate new eruptive activity or rising magma. Seismicity remained slightly above background levels through the end of 2016, and the ACC remained at Yellow.

Geologic Background. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.dggs.alaska.gov/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845(URL: http://www.ssd.noaa.gov/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); Colt Snapp (URL: https://twitter.com/colt_snapp/status/714345047173369856); The Canadian Press, via Vancouver Observer (URL: http://www.vancouverobserver.com/news/environment/flights-cancelled-and-out-regina-yellowknife-after-volcano-alaska); NBC News (URL: http://www.nbcnews.com/news/weather/pavlof-volcano-erupts-covering-400-miles-alaska-ash-n546956).

Poás is characterized by intermittent explosions from its hot crater lake. Several occurred in 2014 (BGVN 40:11). This report covers activity from 1 January 2015 through February 2017. There were no reports of activity during 2015 through May 2016. Phreatic eruptions were recorded between 5 June and 16 August 2016.

According to news articles (La Prensa Libre, Prensa Latina), phreatic explosions from the hot crater lake occurred multiple times in June 2016. Explosions at 0900 on 5 June, at 1854 on 13 June, and at 1952 on 14 June ejected water and steam many meters above the lake's surface. Three small explosions, lasting about five seconds each based on the seismic signals, occurred during 0600-0603 on 18 June and ejected water, steam, and debris no more than 50 m above the lake's surface. Phreatic explosions were also registered on 19 June.

According to the Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA), a small phreatic explosion from the lake was recorded at 0819 on 25 July 2016. The explosion ejected material 50 m above the lake surface.

News accounts (Q Costa Rica, La Prensa Libre) reported that at 1409 local time on 16 August 2016 an explosion sent a column of gas to a height of 100 m above the crater; the activity lasted 2 minutes. An OVSICORI-UNA video of this explosion was posted in the news articles.

Geologic Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); La Prensa Libre (URL: https://www.laprensalibre.cr/); Prensa Latina (URL: http://www.plenglish.com/); Q Costa Rica News (URL: http://qcostarica.com/).

An eruption at Sheveluch has been ongoing since 1999, and recent activity there was previously described through August 2015 (BGVN 42:02). During September 2015-February 2016, the same type of activity prevailed, with lava dome extrusion, incandescence, hot block avalanches, fumarolic activity, and occasional strong explosions that generated ash plumes. The following data comes from Kamchatka Volcanic Eruption Response Team (KVERT) reports. During this period the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

KVERT reported that during 1 September 2015-28 February 2016, lava-dome extrusion onto the N flank was accompanied by fumarolic activity, dome incandescence, hot avalanches, and ash explosions. Satellite images detected an almost daily, and sometimes intense, thermal anomaly over the dome. Ash plumes generated by occasional explosions, hot avalanches, and sometimes strong winds rose to altitudes of 2.5-7 km and drifted primarily SE during September-December 2015 (up to 185 km) and in more variable directions (up to 200 km) during January-March 2016. A series of photos taken in late 2015 shows characteristic types of activity, including small explosions and hot avalanches on 28 October (figure 39), an explosion and pyroclastic flow on 22 November (figure 40), and incandescence on 25 November (figure 41).

Figure 39. Photo of Sheveluch during a sequence of small explosions and hot avalanches from the lava dome's E flank that sent ash up to 4 km altitude on 28 October 2015. Ash can be seen falling out of the plume on the lower flank. Courtesy of Y. Demyanchuk, Institute Volcanology and Seismology FEB RAS, KVERT.

Figure 40. Photo of Sheveluch with an ash plume rising during a larger explosion and a pyroclastic flow moving down the SW flank of the lava dome on 22 November 2015. Courtesy of Y. Demyanchuk, Institute Volcanology and Seismology FEB RAS, KVERT.

Figure 41. Photo showing a strong fumarolic plume from Sheveluch and incandescence caused by hot avalanches from the lava dome on 25 November 2015. Courtesy of Y. Demyanchuk, Institute Volcanology and Seismology FEB RAS, KVERT.

Thermal anomalies based on MODIS satellite instruments analyzed using the MODVOLC algorithm were frequent during the current reporting period, in contrast to March-August 2015 (BGVN 42:02). From September 2015-February 2016, thermal anomalies were detected 10-15 days each month. On 22 November, seven pixels were recorded.

Geologic Background. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far East Division, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).

Soputan stratovolcano on the northern tip of Indonesia's island of Sulawesi has had historically observed eruptions since the 18th century, possibly earlier. The locus of eruptions has included both the summit crater and a NE-flank vent that was active during 1906-1924. Since the 1980's, continuing lava-dome growth has been punctuated by ash explosions, lava flows, and Strombolian eruptions every few years. When these events last occurred between January and March 2015, they were accompanied by strong thermal anomalies and elevated seismicity which continued into early July 2015 (BGVN 41:05). This report covers the period from July 2015 through September 2016.

Increased seismicity in November 2015 signaled the beginning of a new eruptive episode, with explosions in January and February 2016. Soputan is monitored by PVMBG (Pusat Vulkanologi dan Mitigasi Bencana Geologi), Badan Nasional Penanggulangan Bencana (BNPB) which is the Indonesian National Disaster Management Agency, and aviation alerts are managed by the Darwin VAAC (Volcanic Ash Advisory Center). Information is also provided by the University of Hawaii's MODVOLC Thermal Alert System and the MIROVA project, an Italian collaboration; both groups analyze the MODIS satellite data for thermal anomalies related to volcanoes.

Soputan erupted a significant ash plume to over 12 km altitude on 4 January 2016 after a few months of increasing seismicity. Lava flows, Strombolian eruptions, and a pyroclastic flow were observed the next day. Another large ash plume to 13 km altitude occurred on 14 January. A series of explosions beginning on 6 February resulted in more ash plumes, lava flows, and Strombolian eruptions for about 24 hours, after which activity decreased significantly. Several villages within 20 km reported ashfall from these events. The last reported activity was on 7 February 2016, although thermal anomaly data extended well into April. Seismicity had declined significantly by mid-April when the Alert Level was lowered.

Activity during July-November 2015. PVMBG lowered the Alert Level to II (second lowest on a four-level scale) on 3 July 2015, citing reduced harmonic tremor and stable RSAM (Real-time Seismic amplitude measurements) at background levels compared with the eruptive activity between January and March 2015. They did not issue another update until 3 November 2015.

MODVOLC thermal alert information from MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data indicated anomalies in the vicinity of Soputan twice in September and four times in October 2015, but the locations were far enough from the volcano to suggest that they were not related to volcanic activity. This is corroborated with the MIROVA (Middle InfraRed Observation of Volcanic Activity) data from this same period which also recorded increases in Volcanic Radiative Power (VRP) in September and October. The locations indicated by MIROVA are mostly greater than 5 km from the summit, also suggesting a non-volcanic source (figure 12).

Figure 12. MIROVA analysis of MODIS data for 6 September 2015 through 6 September 2016 for Soputan. Moderate to High values in September and October 2015 are noted in black, indicating sources more than 5 km from the volcano and likely not related to eruptive activity. Low values in blue between 6 September and mid-December are from an unknown source within 5 km of the summit. The spikes on 4-6 January 2016 and 6-8 February correspond to observed ash plumes, lava flows, pyroclastic flows, and Strombolian eruptions reported by PVMBG. Courtesy of MIROVA.

Additional thermal anomaly signals in the MIROVA data from mid-September through early December 2015 appear to be sourced within 5 km of the summit (figure 12), but their origin is unknown. PVMBG makes no mention of active eruptions or ash plumes during this time. PVMBG maintained the Level II alert status and documented clear skies with diffuse white steam plumes rising between 20 and 200 m from the summit crater during the last half of October and November, unchanged since July. They noted, however, that the frequency of several types of earthquakes began a gradual increase in the middle of October.

Activity during January-September 2016. Elevated seismicity continued until 4 January 2016. Photos taken on 3 and 4 January showed an increase in the density of the white-to-light-gray emissions rising to 300 m above the summit (figure 13).

Figure 13. Emissions (white to light-gray) rise from Soputan on 3 January 2016, about 24 hours prior to a significant ash eruption (colors adjusted from original image). Courtesy of PVMBG (Soputan activity report through 4 January 2016).

Dense reddish-white emissions rose 300 m above the summit early in the day on 4 January. A thermal image taken that day indicated that lava was present at the summit; PVMBG raised the Alert Level to III. Seismic amplitude (RSAM) values had also increased sharply in the preceding 12 hours, and tilt measurement data indicated significant inflation of the volcano. BNPB reported an ash eruption at 2053 local time, with a plume rising 2 km from the summit and drifting SE, and incandescent lava flowing down the E flank. Minor ashfall was reported in Langowan (12 km NE) in the Minahasa District. The Darwin VAAC raised the Aviation Color Code (ACC) to Red at 2230 local time and reported an ash plume at 12.8 km altitude drifting west 30 minutes later. This was followed in the next 24 hours by two more plumes that rose to 10.6 km and drifted NW to NE (figure 14). Continuous emissions rising to about 3.7 km were observed until early 7 January.

Figure 14. Soputan eruption during the morning hours of 5 January 2016 (local time). Photograph location uncertain but likely taken in the vicinity of Ronoketang, about 12 km S. Courtesy of PVMBG.

A Strombolian phase early on 5 January lasted about 40 minutes and sent incandescent material 250 m high, according to BNPB. Sounds resembling thunder followed, and then a pyroclastic flow traveled 2.5 km down the ENE flank. An ash cloud rose 6.5 km above the summit crater rim (8.3 km altitude) and drifted W. Several villages in the districts of West Langowan (8 km E), Tompaso (11 km NE), and East Ratahan (14 km SE) reported ashfall.

MODVOLC thermal alert pixels likely associated with the eruption were reported during 6-8 January. A small cluster on 10 January located on the NE flank possibly indicated flowing or cooling lava. The Darwin VAAC reported another large ash plume on 14 January that rose to 13.7 km and drifted 45 km NE before dissipating.

A new series of explosions began on 6 February 2016. Ash plumes rose to 7 km altitude, later dropping to the range of 4.3-6 km, with continuous emissions drifting up to 75 km WSW through the next day. PVMBG reported lava flows on the N and E flanks; Strombolian explosions witnessed from the observation post in the village of Silian (about 10 km from the volcano) ejected material 300 m high. BNPB reported Strombolian activity on 7 February with ejected material as high as 1,000 m above the summit crater. Pyroclastic flows were also observed moving up to 2 km down the E flank. Seismic amplitudes remained high, indicating the active movement of magma within the volcano. Ashfall was reported in multiple districts including Pasan (5 km SSE), Tombatu (16 km SSW), Belang (17 km SSE), and Ratatotok (20 km S). The MODIS thermal anomaly data resulted in a very strong (32 pixel) MODVOLC thermal alert on 6 February. This corresponded with the Volcanic Radiative Power (VRP) spike presented in the MIROVA information for the same period (figure 12).

For the rest of February, only diffuse white steam plumes rose 75 m, except for a 700-m-high plume reported on 12 February by PVMBG; three MODVOLC thermal alert pixels were recorded on 11 and one on 13 February. Minor steam emissions rose to 100 m at the end of March, but the frequency of earthquakes associated with avalanches and low-frequency earthquakes were still elevated above background levels. The intensity of the avalanche-related earthquakes began to decline in the second week in April according to PVMBG. No incandescence was observed at the summit by the third week of April, and the decreasing frequency and amplitude of the earthquakes led PVMBG to lower the Alert Level to II on 21 April 2016. Between May and mid-September 2016, emissions from the volcano were characterized by white plumes of variable density ranging from 20 to 300 m above the crater and seismicity remained low (figure 15). The Alert Level remained at II.

Figure 15. Seismicity at Soputan from 1 January 2015 through 14 September 2016. Dates of eruptive events are shown with red bars. Vertical axis on all graphs is daily frequency. LETUSAN is eruption, vertical axis on the right is height in meters above summit of ash plume observed by PVMBG; HEMBUSAN is emission related seismicity; GUGURAN is seismicity associated with rock avalanches; VULKANIK DANGKAL are shallow volcanic earthquakes; VULKANIK DALAM are deep volcanic earthquakes; TECTONIK JAUH are remote tectonic earthquakes. Courtesy of PVMBG (Soputan Report of activity through 14 September 2016).

Geologic Background. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano is located SW of Riendengan-Sempu, which some workers have included with Soputan and Manimporok (3.5 km ESE) as a volcanic complex. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38 East Jakarta 13120 (URL: http://www.bnpb.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

In discussing the week ending on 12 September, "Earthweek" (Newman, 1997) incorrectly claimed that a volcano named "Mount Pinukis" had erupted. Widely read in the US, the dramatic Earthweek report described terrified farmers and a black mushroom cloud that resembled a nuclear explosion. The mountain's location was given as "200 km E of Zamboanga City," a spot well into the sea. The purported eruption had received mention in a Manila Bulletin newspaper report nine days earlier, on 4 September. Their comparatively understated report said that a local police director had disclosed that residents had seen a dormant volcano showing signs of activity.

In response to these news reports Emmanuel Ramos of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) sent a reply on 17 September. PHIVOLCS staff had initially heard that there were some 12 alleged families who fled the mountain and sought shelter in the lowlands. A PHIVOLCS investigation team later found that the reported "families" were actually individuals seeking respite from some politically motivated harassment. The story seems to have stemmed from a local gold rush and an influential politician who wanted to use volcanism as a ploy to exclude residents. PHIVOLCS concluded that no volcanic activity had occurred. They also added that this finding disappointed local politicians but was much welcomed by the residents.

PHIVOLCS spelled the mountain's name as "Pinokis" and from their report it seems that it might be an inactive volcano. There is no known Holocene volcano with a similar name (Simkin and Siebert, 1994). No similar names (Pinokis, Pinukis, Pinakis, etc.) were found listed in the National Imagery and Mapping Agency GEOnet Names Server (http://geonames.nga.mil/gns/html/index.html), a searchable database of 3.3 million non-US geographic-feature names.

The Manila Bulletin report suggested that Pinokis resides on the Zamboanga Peninsula. The Peninsula lies on Mindanao Island's extreme W side where it bounds the Moro Gulf, an arm of the Celebes Sea. The mountainous Peninsula trends NNE-SSW and contains peaks with summit elevations near 1,300 m. Zamboanga City sits at the extreme end of the Peninsula and operates both a major seaport and an international airport.

[Later investigation found that Mt. Pinokis is located in the Lison Valley on the Zamboanga Peninsula, about 170 km NE of Zamboanga City and 30 km NW of Pagadian City. It is adjacent to the two peaks of the Susong Dalaga (Maiden's Breast) and near Mt. Sugarloaf.]

References. Newman, S., 1997, Earthweek, a diary of the planet (week ending 12 September): syndicated newspaper column (URL: http://www.earthweek.com/).

Manila Bulletin, 4 Sept. 1997, Dante's Peak (URL: http://www.mb.com.ph/).

Simkin, T., and Siebert, L., 1994, Volcanoes of the world, 2nd edition: Geoscience Press in association with the Smithsonian Institution Global Volcanism Program, Tucson AZ, 368 p.

Information Contacts: Emmanuel G. Ramos, Deputy Director, Philippine Institute of Volcanology and Seismology, Department of Science and Technology, PHIVOLCS Building, C. P. Garcia Ave., University of the Philippines, Diliman campus, Quezon City, Philippines.

Xinhua News Agency filed a news report on 27 February under the headline "Volcano erupts in Somalia" but the veracity of the story now appears doubtful. The report disclosed the volcano's location as on the W side of the Gedo region, an area along the Ethiopian border just NE of Kenya. The report had relied on the commissioner of the town of Bohol Garas (a settlement described as 40 km NE of the main Al-Itihad headquarters of Luq town) and some or all of the information was relayed by journalists through VHF radio. The report claimed the disaster "wounded six herdsmen" and "claimed the lives of 290 goats grazing near the mountain when the incident took place." Further descriptions included such statements as "the volcano which erupted two days ago [25 February] has melted down the rocks and sand and spread . . . ."

Giday WoldeGabriel returned from three weeks of geological fieldwork in SW Ethiopia, near the Kenyan border, on 25 August. During his time there he inquired of many people, including geologists, if they had heard of a Somalian eruption in the Gedo area; no one had heard of the event. WoldeGabriel stated that he felt the news report could have described an old mine or bomb exploding. Heavy fighting took place in the Gedo region during the Ethio-Somalian war of 1977. Somalia lacks an embassy in Washington DC; when asked during late August, Ayalaw Yiman, an Ethiopian embassy staff member in Washington DC also lacked any knowledge of a Somalian eruption.

A Somalian eruption would be significant since the closest known Holocene volcanoes occur in the central Ethiopian segment of the East African rift system S of Addis Ababa, ~500 km NW of the Gedo area. These Ethiopian rift volcanoes include volcanic fields, shield volcanoes, cinder cones, and stratovolcanoes.

Information Contacts: Xinhua News Agency, 5 Sharp Street West, Wanchai, Hong Kong; Giday WoldeGabriel, EES-1/MS D462, Geology-Geochemistry Group, Los Alamos National Laboratory, Los Alamos, NM 87545; Ayalaw Yiman, Ethiopian Embassy, 2134 Kalorama Rd. NW, Washington DC 20008.

Following the Ms 7.8 earthquake in Turkey on 17 August (BGVN 24:08) an Email message originating in Turkey was circulated, claiming that volcanic activity was observed coincident with the earthquake and suggesting a new (magmatic) volcano in the Sea of Marmara. For reasons outlined below, and in the absence of further evidence, editors of the Bulletin consider this a false report.

The report stated that fishermen near the village of Cinarcik, at the E end of the Sea of Marmara "saw the sea turned red with fireballs" shortly after the onset of the earthquake. They later found dead fish that appeared "fried." Their nets were "burned" while under water and contained samples of rocks alleged to look "magmatic."

No samples of the fish were preserved. A tectonic scientist in Istanbul speculated that hot water released by the earthquake from the many hot springs along the coast in that area may have killed some fish (although they would be boiled rather than fried).

The phenomenon called earthquake lights could explain the "fireballs" reportedly seen by the fishermen. Such effects have been reasonably established associated with large earthquakes, although their origin remains poorly understood. In addition to deformation-triggered piezoelectric effects, earthquake lights have sometimes been explained as due to the release of methane gas in areas of mass wasting (even under water). Omlin and others (1999), for example, found gas hydrate and methane releases associated with mud volcanoes in coastal submarine environments.

The astronomer and author Thomas Gold (Gold, 1998) has a website (Gold, 2000) where he presents a series of alleged quotes from witnesses of earthquakes. We include three such quotes here (along with Gold's dates, attributions, and other comments):

(A) Lima, 30 March 1828. "Water in the bay 'hissed as if hot iron was immersed in it,' bubbles and dead fish rose to the surface, and the anchor chain of HMS Volage was partially fused while lying in the mud on the bottom." (Attributed to Bagnold, 1829; the anchor chain is reported to be on display in the London Navy Museum.)

(B) Romania, 10 November 1940. ". . . a thick layer like a translucid gas above the surface of the soil . . . irregular gas fires . . . flames in rhythm with the movements of the soil . . . flashes like lightning from the floor to the summit of Mt Tampa . . . flames issuing from rocks, which crumbled, with flashes also issuing from non-wooded mountainsides." (Phrases used in eyewitness accounts collected by Demetrescu and Petrescu, 1941).

(C) Sungpan-Pingwu (China), 16, 22, and 23 August 1976. "From March of 1976, various large anomalies were observed over a broad region. . . . At the Wanchia commune of Chungching County, outbursts of natural gas from rock fissures ignited and were difficult to extinguish even by dumping dirt over the fissures. . . . Chu Chieh Cho, of the Provincial Seismological Bureau, related personally seeing a fireball 75 km from the epicenter on the night of 21 July while in the company of three professional seismologists."

Yalciner and others (1999) made a study of coastal areas along the Sea of Marmara after the Izmet earthquake. They found evidence for one or more tsunamis with maximum runups of 2.0-2.5 m. Preliminary modeling of the earthquake's response failed to reproduce the observed runups; the areas of maximum runup instead appeared to correspond most closely with several local mass-failure events. This observation together with the magnitude of the earthquake, and bottom soundings from marine geophysical teams, suggested mass wasting may have been fairly common on the floor of the Sea of Marmara.

Despite a wide range of poorly understood, dramatic processes associated with earthquakes (Izmet 1999 apparently included), there remains little evidence for volcanism around the time of the earthquake. The nearest Holocene volcano lies ~200 km SW of the report location. Neither Turkish geologists nor scientists from other countries in Turkey to study the 17 August earthquake reported any volcanism. The report said the fisherman found "magmatic" rocks; it is unlikely they would be familiar with this term.

The motivation and credibility of the report's originator, Erol Erkmen, are unknown. Certainly, the difficulty in translating from Turkish to English may have caused some problems in understanding. Erkmen is associated with a website devoted to reporting UFO activity in Turkey. Photographs of a "magmatic rock" sample were sent to the Bulletin, but they only showed dark rocks photographed devoid of a scale on a featureless background. The rocks shown did not appear to be vesicular or glassy. What was most significant to Bulletin editors was the report author's progressive reluctance to provide samples or encourage follow-up investigation with local scientists. Without the collaboration of trained scientists on the scene this report cannot be validated.

References. Omlin, A, Damm, E., Mienert, J., and Lukas, D., 1999, In-situ detection of methane releases adjacent to gas hydrate fields on the Norwegian margin: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Yalciner, A.C., Borrero, J., Kukano, U., Watts, P., Synolakis, C. E., and Imamura, F., 1999, Field survey of 1999 Izmit tsunami and modeling effort of new tsunami generation mechanism: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Gold, T., 1998, The deep hot biosphere: Springer Verlag, 256 p., ISBN: 0387985468.

Gold, T., 2000, Eye-witness accounts of several major earthquakes (URL: http://www.people.cornell.edu/ pages/tg21/eyewit.html).

Information Contacts: Erol Erkmen, Tuvpo Project Alp.

In December 2002 information appeared in Mongolian and Russian newspapers and on national TV that a volcano in Central Mongolia, the Har-Togoo volcano, was producing white vapors and constant acoustic noise. Because of the potential hazard posed to two nearby settlements, mainly with regard to potential blocking of rivers, the Director of the Research Center of Astronomy and Geophysics of the Mongolian Academy of Sciences, Dr. Bekhtur, organized a scientific expedition to the volcano on 19-20 March 2003. The scientific team also included M. Ulziibat, seismologist from the same Research Center, M. Ganzorig, the Director of the Institute of Informatics, and A. Ivanov from the Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences.

Geological setting. The Miocene Har-Togoo shield volcano is situated on top of a vast volcanic plateau (figure 1). The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Pliocene and Quaternary volcanic rocks are also abundant in the vicinity of the Holocene volcanoes (Devyatkin and Smelov, 1979; Logatchev and others, 1982). Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Figure 1. Photograph of the Har-Togoo volcano viewed from west, March 2003. Courtesy of Alexei Ivanov.

Observations during March 2003. The name of the volcano in the Mongolian language means "black-pot" and through questioning of the local inhabitants, it was learned that there is a local myth that a dragon lived in the volcano. The local inhabitants also mentioned that marmots, previously abundant in the area, began to migrate westwards five years ago; they are now practically absent from the area.

Acoustic noise and venting of colorless warm gas from a small hole near the summit were noticed in October 2002 by local residents. In December 2002, while snow lay on the ground, the hole was clearly visible to local visitors, and a second hole could be seen a few meters away; it is unclear whether or not white vapors were noticed on this occasion. During the inspection in March 2003 a third hole was seen. The second hole is located within a 3 x 3 m outcrop of cinder and pumice (figure 2) whereas the first and the third holes are located within massive basalts. When close to the holes, constant noise resembled a rapid river heard from afar. The second hole was covered with plastic sheeting fixed at the margins, but the plastic was blown off within 2-3 seconds. Gas from the second hole was sampled in a mechanically pumped glass sampler. Analysis by gas chromatography, performed a week later at the Institute of the Earth's Crust, showed that nitrogen and atmospheric air were the major constituents.

Figure 2. Photograph of the second hole sampled at Har-Togoo, with hammer for scale, March 2003. Courtesy of Alexei Ivanov.

The temperature of the gas at the first, second, and third holes was +1.1, +1.4, and +2.7°C, respectively, while air temperature was -4.6 to -4.7°C (measured on 19 March 2003). Repeated measurements of the temperatures on the next day gave values of +1.1, +0.8, and -6.0°C at the first, second, and third holes, respectively. Air temperature was -9.4°C. To avoid bias due to direct heating from sunlight the measurements were performed under shadow. All measurements were done with Chechtemp2 digital thermometer with precision of ± 0.1°C and accuracy ± 0.3°C.

Inside the mouth of the first hole was 4-10-cm-thick ice with suspended gas bubbles (figure 5). The ice and snow were sampled in plastic bottles, melted, and tested for pH and Eh with digital meters. The pH-meter was calibrated by Horiba Ltd (Kyoto, Japan) standard solutions 4 and 7. Water from melted ice appeared to be slightly acidic (pH 6.52) in comparison to water of melted snow (pH 7.04). Both pH values were within neutral solution values. No prominent difference in Eh (108 and 117 for ice and snow, respectively) was revealed.

Two digital short-period three-component stations were installed on top of Har-Togoo, one 50 m from the degassing holes and one in a remote area on basement rocks, for monitoring during 19-20 March 2003. Every hour 1-3 microseismic events with magnitude <2 were recorded. All seismic events were virtually identical and resembled A-type volcano-tectonic earthquakes (figure 6). Arrival difference between S and P waves were around 0.06-0.3 seconds for the Har-Togoo station and 0.1-1.5 seconds for the remote station. Assuming that the Har-Togoo station was located in the epicentral zone, the events were located at ~1-3 km depth. Seismic episodes similar to volcanic tremors were also recorded (figure 3).

Figure 3. Examples of an A-type volcano-tectonic earthquake and volcanic tremor episodes recorded at the Har-Togoo station on 19 March 2003. Courtesy of Alexei Ivanov.

Conclusions. The abnormal thermal and seismic activities could be the result of either hydrothermal or volcanic processes. This activity could have started in the fall of 2002 when they were directly observed for the first time, or possibly up to five years earlier when marmots started migrating from the area. Further studies are planned to investigate the cause of the fumarolic and seismic activities.

At the end of a second visit in early July, gas venting had stopped, but seismicity was continuing. In August there will be a workshop on Russian-Mongolian cooperation between Institutions of the Russian and Mongolian Academies of Sciences (held in Ulan-Bator, Mongolia), where the work being done on this volcano will be presented.

References. Devyatkin, E.V. and Smelov, S.B., 1979, Position of basalts in sequence of Cenozoic sediments of Mongolia: Izvestiya USSR Academy of Sciences, geological series, no. 1, p. 16-29. (In Russian).

Logatchev, N.A., Devyatkin, E.V., Malaeva, E.M., and others, 1982, Cenozoic deposits of Taryat basin and Chulutu river valley (Central Hangai): Izvestiya USSR Academy of Sciences, geological series, no. 8, p. 76-86. (In Russian).

Geologic Background. The Miocene Har-Togoo shield volcano, also known as Togoo Tologoy, is situated on top of a vast volcanic plateau. The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Information Contacts: Alexei V. Ivanov, Institute of the Earth Crust SB, Russian Academy of Sciences, Irkutsk, Russia; Bekhtur andM. Ulziibat, Research Center of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulan-Bator, Mongolia; M. Ganzorig, Institute of Informatics MAS, Ulan-Bator, Mongolia.

An eruption at Mount Elgon was mistakenly inferred when fumes escaped from this otherwise quiet volcano. The fumes were eventually traced to dung burning in a lava-tube cave. The cave is home to, or visited by, wildlife ranging from bats to elephants. Mt. Elgon (Ol Doinyo Ilgoon) is a stratovolcano on the SW margin of a 13 x 16 km caldera that straddles the Uganda-Kenya border 140 km NE of the N shore of Lake Victoria. No eruptions are known in the historical record or in the Holocene.

On 7 September 2004 the web site of the Kenyan newspaper The Daily Nation reported that villagers sighted and smelled noxious fumes from a cave on the flank of Mt. Elgon during August 2005. The villagers' concerns were taken quite seriously by both nations, to the extent that evacuation of nearby villages was considered.

The Daily Nation article added that shortly after the villagers' reports, Moses Masibo, Kenya's Western Province geology officer visited the cave, confirmed the villagers observations, and added that the temperature in the cave was 170°C. He recommended that nearby villagers move to safer locations. Masibo and Silas Simiyu of KenGens geothermal department collected ashes from the cave for testing.

Gerald Ernst reported on 19 September 2004 that he spoke with two local geologists involved with the Elgon crisis from the Geology Department of the University of Nairobi (Jiromo campus): Professor Nyambok and Zacharia Kuria (the former is a senior scientist who was unable to go in the field; the latter is a junior scientist who visited the site). According to Ernst their interpretation is that somebody set fire to bat guano in one of the caves. The fire was intense and probably explains the vigorous fuming, high temperatures, and suffocated animals. The event was also accompanied by emissions of gases with an ammonia odor. Ernst noted that this was not surprising considering the high nitrogen content of guano—ammonia is highly toxic and can also explain the animal deaths. The intense fumes initially caused substantial panic in the area.

It was Ernst's understanding that the authorities ordered evacuations while awaiting a report from local scientists, but that people returned before the report reached the authorities. The fire presumably prompted the response of local authorities who then urged the University geologists to analyze the situation. By the time geologists arrived, the fuming had ceased, or nearly so. The residue left by the fire and other observations led them to conclude that nothing remotely related to a volcanic eruption had occurred.

However, the incident emphasized the problem due to lack of a seismic station to monitor tectonic activity related to a local triple junction associated with the rift valley or volcanic seismicity. In response, one seismic station was moved from S Kenya to the area of Mt. Elgon so that local seismicity can be monitored in the future.

Information Contacts: Gerald Ernst, Univ. of Ghent, Krijgslaan 281/S8, B-9000, Belgium; Chris Newhall, USGS, Univ. of Washington, Dept. of Earth & Space Sciences, Box 351310, Seattle, WA 98195-1310, USA; The Daily Nation (URL: http://www.nationmedia.com/dailynation/); Uganda Tourist Board (URL: http://www.visituganda.com/).