Intermittent low-level ash plumes, light ashfall, and thermal anomalies during January-August 2021

Ibu is located along the NW coast of Halmahera Island in Indonesia and contains an inner crater measuring 1-km-wide and 400 m deep, an outer crater that measures 1.2-km-wide, and is breached on the N side. The first observed and recorded eruption occurred in 1911 and consisted of a small explosion in the summit crater. The current eruption period began in April 2008 and has recently been characterized by daily ash emissions, explosions, and thermal anomalies (BGVN 46:01). This report covers similar activity of white-and-gray emissions, ash plumes, and light ashfall during January through August 2021 using information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC), and various satellite data. The Volcano Alert Level remained at a 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater and 3.5 km away on the N side.

Activity throughout January-August 2021 was consistent and similar to that of the previous year. Between 35 and 115 daily explosions were detected during the reporting period, the latter of which occurred on 7 February, and produced white-and-gray emissions that rose 200-1,000 m above the crater and drifted in different directions, according to PVMBG. Occasional larger explosions were reported in VONA and VAAC notices. According to the MIROVA plot (Log Radiative Power), thermal activity was consistent, yet low in power from January through August; during May, the anomalies were at their lowest strength (figure 31). The MODVOLC algorithm detected ten thermal alerts during this period, with one each on 1 February, 9 March, 22 April, 2 and 27 June, 29 July, and 12 August, and three on 23 August 2021. Some of this thermal activity was detected in Sentinel-2 infrared satellite images on clear weather days (figure 32).

Figure 31. Constant low-power thermal anomalies were detected at the summit crater of Ibu during January through August 2021, as shown by the MIROVA graph (Log Radiative Power). Courtesy of MIROVA.

Figure 32. Thermal anomalies persisted in the summit crater of Ibu during January through August 2021. One strong central anomaly was commonly accompanied by a smaller one slightly to the NW, as shown on 10 January (top left), 1 March (top right), 5 April (middle left), and 8 August (bottom right) 2021. Images using “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

The Darwin VAAC detected a single minor ash plume on 7 January that rose to 1.8 km altitude, or about 500 m above the summit, and drifted N, based on a ground report. This information was also reported in a PVMBG VONA notice that stated the ash plume occurred at 1055. Similar low-level ash plumes persisted in February; during 5-6 February ash plumes rose to 1.8-2.4 km and drifted W and SW, based on HIMAWARI-8 satellite imagery. An ash plume rose 800 m above the crater on 8 February on 1101, according to a VONA notice. PVMBG reported that during 16-17 February a total of 88 eruptive events occurred. Consecutive ash plumes on 24, 25, and 26 February rose 500, 800, and 800 m above the crater, respectively (figure 33).

Figure 33. An ash plume rose from the summit of Ibu on 25 February 2021 to a height of 800 m. Courtesy of MAGMA Indonesia.

Similar intermittent ash emissions continued during March and April. On 3, 9, and 12 March an ash plume rose to 2.1 km and drifted S, according to Darwin VAAC notices (figure 34). During 14, 21, 25, and 31 March ash plumes rose 600-1,000 m above the crater, based on VONA notices and PVMBG daily reports. A thermal anomaly was detected in satellite imagery near the summit on 22 March and 6-7 April, according to a Darwin VAAC report. Accompanying the latter thermal anomaly, at 1812 a VONA notice reported an ash plume rose 400 m above the crater. An ash plume rose 800 m above the crater on 20 April at 1819 and another detected on 22 April at 1258 rose 1,000 m above the crater. On 26 April an ash plume rose 600 m above the crater and drifted N.

Figure 34. Intermittent ash plumes rising above the summit of Ibu were recorded multiple times in webcam images during March and April 2021, as shown here on 3 March 2021 rising to 2.1 km altitude and drifting S. Courtesy of MAGMA Indonesia.

During May and June, activity remained consistent with intermittent ash emissions. On 3 and 12 May an ash plume rose to 1.8 km altitude and drifted W and NW, based on HIMAWARI-8 satellite imagery. Ash plumes were visible during 16 (figure 35) and 17 May, the latter of which occurred at 1039 and rose ~750 m above the crater and drifted N. During the afternoon and evening of 19 May, light ashfall was reported in residential areas from the Naga village (4.8 km SW) to the Tongute village of Ternate (10 km W). On 6 and 10 June ash emissions rose to 1.8 km altitude and extended N. Rock avalanches were recorded through seismic data during 11-13 June, though they were not visually confirmed, according to PVMBG. During 18-20 June 63 eruptive events per day were detected.

Figure 35. Ash plumes from the summit of Ibu continued during May and June 2021, as seen here on 16 May 2021. Courtesy of MAGMA Indonesia.

Low ash emissions continued during July and August; on 10 July at 0719 an ash plume rose 800 m above the crater and the next day, light ashfall was reported in residential areas to the W of the volcano, though it was not specified how far. During 14-15 and 17 July white-and-gray emissions rose 200-800 m above the crater and drifted N, S, and W; light ashfall was again observed in residential areas to the W, and loud rumblings were heard as far as the Ibu observation post. On 28 July an ash plume rose to 2.4 km altitude and extended NE. During 1-2 August an ash plume rose to 1.8-2.1 km altitude. An ash plume on 18 August was reported at 0810 rising 800 m above the crater and drifting W. An ash plume on 22 August rose to 1.8 km altitude and was accompanied by a thermal anomaly that was identified in satellite imagery.

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.esdm.go.id/v1); 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/); 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).

Information is preliminary and subject to change. All times are local (unless otherwise noted)

January 1999 (BGVN 24:01) Cite this Report

First eruption since 1911 is being monitored

Ibu volcano on Halmahera island started erupting on 31 December 1998. A plume rose to 1,000 m above the summit as a result of mild explosions. On 2 January, personnel from the Volcanological Survey of Indonesia (VSI) who went to the island to take COSPEC measurements observed an eruption. Ashes were deposited to ~3 mm depth in surrounding villages. On 5 January another eruption lasted for 60 minutes. Local people reported that a lava flow reached the lower lip of the crater on 16 January.

Information Contacts: R. Sukhyar and Dali Ahmad Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No.57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).

February 1999 (BGVN 24:02) Cite this Report

Eruptions that began on 18 December 1998 continued in January 1999

Local residents first noticed thick gray ash emissions from the summit on 18 December 1998 (corrected from BGVN 24:01); this information reached the Volcanological Survey of Indonesia (VSI) Gamkonora volcano observatory on the 31st. On 2 January personnel from VSI who went to the island to take COSPEC measurements of the SO₂ release observed a loud eruption that caused up to 3 mm of ashfall in and around Tugure Batu Village. The eruption lasted 35 minutes and generated a plume 1,000 m high. Another eruption observed on 5 January 1999 lasted for 60 minutes. Thunderclaps from the summit were heard on 16 January and a night glow from ejecta was evident above the summit area. Residents also reportedly saw lava at the crater rim. The seismometer from Gamkonora (an RTS PS-2) was installed ~2 km from the summit of Ibu on 3 February along with an ARGOS satellite system tiltmeter.

Field observations on 11 March revealed continuing eruptions and rumbling noises, but the larger eruptions (accompanied by booming and thick ash ejection) had decreased to a rate of one every 15-20 minutes. When observed on 2 February larger eruptions occurred every 5 minutes. Seismograph records are still dominated by explosion events; during 9-15 March there were 779 events, increased from 673 events the previous week.

Information Contacts: R. Sukhyar and Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).

May 1999 (BGVN 24:05) Cite this Report

March-May ash plumes are white and rise up to 700 m above crater rim

"White ash emissions" were noted between 9 March and 24 May, rising as high as 700 m above the crater rim but more often 100-200 m. On 11 March it was noted that larger eruptions, accompanied by booming noises and thick ash emission, had decreased to every 10-15 minutes from every 5 minutes during the previous observations on 2 February. Signals from seismic events were dominated by those from the eruptive events, which occurred at a rate of over 100 per day in March and reduced to half that number in April and May.

Information Contacts: Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).

March 2003 (BGVN 28:03) Cite this Report

Infrared satellite data indicates activity during May-October 2001

The last reported activity at Ibu included ash emission and mild ash explosions in September 1999. A May 2000 photo showed a lava dome covering the crater floor. MODIS data after May 2000 indicated thermal alerts during 28 May-3 October 2001 (figure 1). The series of alerts was consistent with continued inflation of, or extrusion onto, this dome. Note that the alert was barely above threshold, and it is likely that Ibu was just below detection threshold through 2002. A discussion of the MODIS technique was included in BGVN 28:01.

Figure 1. MODIS thermal alerts on Ibu during 2001. Thermal alerts collated by Diego Coppola and David Rothery; data courtesy of the Hawaii Institute of Geophysics and Planetology's MODIS Thermal Alert Team.

Information Contacts: Diego Coppola and David A. Rothery, Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA, UK. Thermal alerts courtesy of the HIGP MODIS Thermal Alerts Team (URL: http://modis.higp.hawaii.edu/).

March 2005 (BGVN 30:03) Cite this Report

Periodic ash emissions during June-August 2004 and inferred dome growth

The Directorate of Volcanology and Geological Hazard Mitigation (DVGHM) released ten nearly identical weekly reports on Ibu during 31 May-29 August 2004. They noted that Ibu emitted "white ash" (steam plumes) reaching ~ 50-150 m above the crater rim. Continued growth of the intracrater lava dome was either recognized or assumed. Ibu lacked a working seismic instrument. Its hazard status remained at Level II (Yellow, a condition meaning 'caution or on guard' ('waspada' in Indonesian).

Information Contacts: Directorate of Volcanology and Geological Hazard Mitigation (DVGHM), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).

September 2008 (BGVN 33:09) Cite this Report

Minor ash emissions during June-August 2008 and inferred dome growth

During late March through late April 2008, the Center of Volcanology and Geological Hazard Mitigation (CVGHM) described mainly white plumes emitted from Ibu. On at least five days, however, the plumes were gray. During 17-31 March, frequent white plumes rose to an altitude of 1.5 km. On 31 March the plume altitudes increased to 1.6 km.

During 4-5 April 2008, seismicity increased in amplitude and plume altitude increased to 1.8-2.0 km. On 5 April, the eruption plume was gray and material fell around the crater. Residents of nearby communities were not permitted to climb or approach the crater.

Plumes that were possibly gray rose to altitudes between 1.6 and 1.9 km during 6-17 April. Gray plumes rose to altitudes of 2-2.1 km during 18-21 April. On 21 April, CVGHM warned that residents and tourists were not permitted within 2 km of the crater.

Steam plumes rose above the crater during late May to late August 2004 (BGVN 30:03). Thermal anomalies detected by the MODIS instruments triggered MODVOLC thermal alerts (table 1) during that interval and the last quarter of 2004; alerts were also noted during February 2005, but not in 2006 and 2007. Thermal anomalies were again measured by the MODIS instrument in mid-May 2008 and continued to be detected through late October.

Table 1. MODVOLC thermal anomalies over Ibu from late August 2004 to 20 October 2008. Courtesy of the HIGP Thermal Alerts System.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) 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/).

May 2009 (BGVN 34:05) Cite this Report

Thermal data suggest dome growth continued into mid-2009

Our last report on Ibu summarized MODVOLC thermal alerts (satellite thermal anomalies) from mid-May through late October 2008 (BGVN 33:09); those anomalies continued to be recorded almost monthly through June 2009. The anomalies suggest continued growth of a lava dome in the crater, an event previously documented by a photograph taken May 2000 and mentioned in BGVN 28:03. Authorities raised the hazard alert to Level 3 during June 2008. Several photos of Ibu in 2007 were taken by Arnold Binas (figure 2).

Figure 2. Photos of Ibu taken on 27 July 2007 from a point on the NW crater rim, looking approximately SE. The top photo shows the location of the dome in the steep-walled crater. The bottom photo shows a close-up view of the dome. Courtesy of Arnold Binas.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) 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/); Arnold Binas, Toronto, Canada (URL: http://www.summitpost.org/user_page.php?user_id=42443, http://www.flickr.com/photos/hshdude/collections/72157600584144439/).

October 2009 (BGVN 34:10) Cite this Report

Ongoing dome growth during July-August 2009

Thermal anomalies detected by satellites (MODVOLC thermal alerts) through June 2009 suggested continued growth of a lava dome in the crater (BGVN 34:05). The Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that prior to 11 July 2009, white and gray plumes from Ibu rose ~ 600 m above the crater rim. After 11 July, the plumes were gray and rose only ~ 400 m above the crater rim. Ash from the gray plumes fell on areas within a 3-km radius of Ibu.

Observers noted an increase of eruptive activity after mid-July. During the period 27 July to 3 August, the total number of eruptive events showed a tendency to increase. Each eruptive earthquake was then followed by the expulsion of lava that reached the upper slopes. Plumes seen during 15 July to 4 August 2009 were grayish-white and reached a height of ~ 300-400 m above the crater rim. The lava extrusions accompanied rather strong rumbling noises on five occasions. The incandescent material was seen coming from the summit on 2 August 2009, and lava flows were seen. Later that day, a thunderous sound was followed by incandescence at the summit.

On 3 August, incandescent material was ejected as high as 20 m above the crater. The total of explosion earthquakes increased from the 20-49 events of mid-July to 50-80 events during 27 July to 4 August. Villagers in Desa Duono, Going, and Sanghaji noted strong rumbling sounds. No volcanic earthquakes were recorded during that time frame. On 4 August 2009, 82 volcanic earthquakes were recorded. Each eruptive earthquake was followed by the expulsion of lava which reached the upper slopes.

The observation post in the village of Duono, 5 km NW of Ibu, reported that the lava dome continued to grow. As a result, local residents were advised to prepare for times when they needed to wear masks that cover both the nose and the mouth. Visitors and tourists were asked to remain at least 2 km from the crater.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) 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/).

May 2010 (BGVN 35:05) Cite this Report

Dome growth and small explosions continue in 2010

Activity at Ibu (figure 3) has been frequent since December 1998; the current eruption began in April 2008. Thermal alerts (MODIS/MODVOLC) continued into June 2009, and incandescent ejections were seen in early August (BGVN 34:10).

Figure 3. Location map of Ibu volcano on Halmahera Island. Insert map shows the locations of other active Indonesian volcanoes with triangles. Courtesy of Agustan and others (2010).

Between July 2009 and June 2010, thermal alerts at Ibu were detected by MODVOLC on an average of about five or more days every month (normally one pixel per pass?at least one alert each 55 days during the 1-year period), about the same frequency as those measured during the first half of 2009 and far more frequent than that for the 4-year period October 2004-October 2008 (BGVN 33:09). Ground observations reported below in August-September 2009 and January 2010 confirm continued doem growth.

The Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that white and gray plumes rose 300-400 m above the crater rim during 15 July-4 August 2009 and that earthquakes became more frequent during 27 July-4 August 2009. Lava flows were seen on 2 August. Later that day, a thunderous sound was followed by incandescence at the summit. On 3 August, incandescent material was ejected about 20 m above the crater. The lava dome had reached a height sufficient to be seen from Duono Village, about 5 km NW.

Martin Rietze and Alain de Toffoli took some photographs of Ibu during a 31 August-7 September 2009 visit (figures 4-7), posted on the website of Th. Boeckel. The travelers noted that during the last 10 years the crater has been filled with a lava dome. The volcano has several vents that discharge ash and gas, along with Strombolian ejections. Only two vents were active during the visit.

Figure 4. Photo of the edge of the Ibu crater, taken during 25 August-8 September 2009. The vegetation near the rim was partially charred, and lava from the dome caused small bush fires. Photo taken from the W rim looking toward the E rim. Courtesy of Alain de Toffoli and M. Rietze.

Figure 5. Gas and ash emissions from the growing dome at Ibu, taken during 25 August-8 September 2009. Photo taken from the W rim looking E. Courtesy of Alain de Toffoli and M. Rietze.

Figure 6. Two active vents in Ibu's crater, taken during 25 August-8 September 2009. Photo taken from the W rim looking E. Courtesy of Alain de Toffoli and M. Rietze.

Figure 7. Dome growth in Ibu's crater with Strombolian ejections, taken during 25 August-8 September 2009. Photo taken from the W rim looking E. Courtesy of Alain de Toffoli and M. Rietze.

Arnold Binas posted some photos that demonstrated rapid dome growth (figure 8). Before 1998, the crater was vegetated down to the bottom. The dome was distinctly lower in 2007 (BGVN 34:05). Binas commented that "After a period of no steam emissions at all, [the dome vent] would start steaming slightly to announce it's next eruption. After being done emitting rocks and ash, it would steam vigorously for a while before quieting down again." Binas was also told that material had started to go through a breach in the N side of the crater.

Figure 8. Growth in a single day at Ibu's dome from one of the two vents erupting around 21 January 2010. The top photo was taken during a moment of quiet, and is the older image. Both photos taken from the W rim looking E. Courtesy of Arnold Binas.

A recent article by Agustan and others (2010) used radar to measure ground deformation related to volcanic activity on Ibu. Specifically, they used longer wavelength (L-band) differential interferometry to identify an inflation-deflation region, especially in the crater area before the March-April 2008 eruption (BGVN 33:09).

Reference. Agustan, Kimata, F., Abidin, H.Z., and Pamitro, Y.E., 2010, Measuring ground deformation of the tropical volcano, Ibu, using ALOS-PALSAR data, Remote Sensing Letters, v. 1, issue 1, p. 37-44, DOI: 1080/01431160903246717.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) 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/); Martin Rietze (URL: http://www.mrietze.com/info.htm); Arnold Binas, Toronto, Canada (URL: http://www.flickr.com/photos/hshdude/).

August 2011 (BGVN 36:08) Cite this Report

Frequent minor white-to-gray plumes and small avalanches

Ibu (figure 9) has been intermittently active since 1998. Small explosions were noted during 2009 through January 2010 (BGVN 35:05). This report discuss seismic events from January 2011 to September 2011.

Figure 9. Map showing Ibu volcano, on the island of Halmahera, Indonesia. Courtesy of Google Maps (prepared by GVP editor Jeff Jessens).

According to the Center of Volcanology and Geological Hazard Mitigation (CVGHM), during January 2011 to 8 September 2011, white-to-gray plumes rose 200-400 m above the craters. For 2011, CVGHM reported seismically detected avalanches, which on average occurred 45 times/day during January-April, 60 times/day during May-July, and 46 times/day during the first week of September. During much of 2011 seismicity fluctuated, but decreased towards September, prompting CVGHM to lower the Alert Level to 2 (on a scale of 1-4) on 8 September.

On 20 August 2011, observers from the nearby villages of Goin (exact location undisclosed) and Duono (5 km NW of Ibu) noted multiple eruptions from the S, E, and N craters. Plumes rose 50-250 m above the craters and an avalanche traveled 300 m in undisclosed direction.

During 2010, MODVOLC thermal alerts appeared about once per week on average, whereas, during 1 January 2011 through 13 September 2011, these alerts only appeared about once every 2.4 weeks on average. (Those alerts are derived from satellite data collected by the MODIS instrument and processed by the Hawai'i Institute of Geophysics and Planetology.)

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); 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/).

November 2013 (BGVN 38:11) Cite this Report

Growing lava dome; numerous thermal alerts September 2011-March 2014

In the first nine months of 2011, Ibu was the scene of frequent avalanches and at least one weak explosion that generated minor white-to-gray plumes (BGVN 36:08). Seismic activity decreased during September 2011, prompting the Center of Volcanology and Geological Hazard Mitigation (CVGHM) to lower the Alert Level to 2 (on a scale of 1-4) on 8 September (the Level rose again later). This report discusses activity from 9 September 2011 through March 2014. The location of Ibu is shown in BGVN 36:08.

According to CVGHM, seismicity increased and volcanic tremor was detected during May through 6 June 2013. The lava dome grew, especially the N part, and by early June had grown taller than the N crater rim. White-to-gray plumes rose 200-450 m above the crater rim. Based on visual and instrumental observations, as well as the hazard potential, CVGHM increased the Alert Level to 3 on 7 June. The public was warned to stay at least 3 km away from the active crater.

CVGHM reported that during 7 June-9 December 2013, the lava dome continued to grow, and incandescent material from the dome filled the river valley in the direction of Duono village, about 5 km NW. The seismicity remained relatively stable. Observers saw occasional weak white-to-gray plumes. On 10 December 2013, the Alert Level was lowered to 2; however, the public was warned to stay at least 2 km away from the active crater, and 3.5 km away from the N part.

Between 1 September 2011 and March 2014, MODVOLC thermal alerts were issued on 70 days, or an average of almost one day every two weeks. Such alerts are consistent with dome growth such as that noted above. (Those alerts are derived from satellite data collected by the MODIS instrument and processed by the Hawai'i Institute of Geophysics and Planetology.) For comparison, between 1 January 2011 and 13 September 2011, these alerts only appeared about once every 2.4 weeks on average.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); 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/).

November 2015 (BGVN 40:11) Cite this Report

Continued lava dome growth with occasional weak plumes through November 2015

During the latter half of 2013, Ibu's lava dome continued to grow, and observers noted incandescent material and occasional weak white-to-gray plumes (BGVN 38:11). This report discusses activity between March 2014 and November 2015.

Reports from the Center of Volcanology and Geological Hazard Mitigation (CVGHM) indicated that during 1 August-17 November 2015 white-to-gray plumes rose as high as 500 m above the craters. Seismicity during this period was dominated by signals indicating surface or near-surface activity, and continuing lava dome growth in the N part of the crater. The Alert Level remained at 2 (on a scale of 1-4). The public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side.

Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were observed frequently, and ranged from 1/month (February 2016) to 11/month (July 2014, April 2015, May 2015). Most were one pixel, but three pixels were observed on 5 September 2014 and 22 November 2014. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected numerous, almost continuous anomalies during the past year, though the frequency decreased from almost daily to averaging a few anomalies per week starting in late October 2015.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM, also known as PVMBG), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); 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, 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/).

May 2017 (BGVN 42:05) Cite this Report

Dome growth and ash plumes continue during December 2015-March 2017

Previously reported activity at Ibu through November 2015 included shallow seismicity, lava dome growth on the N part of the crater, and occasional white-to-gray plumes rising as high as 500 m above the summit (BGVN 40:11). This report, describing activity through early March 2017, is based on information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and the Darwin Volcanic Ash Advisory Centre (VAAC).

During the reporting period (at least through 22 Aug 2016), the Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side. Inclement weather often prevented visual observation.

According to PVMBG reports, similar activity to that previously described in 2013-2015 continued through at least 22 August 2016. Seismicity was dominated by signals indicating surface or near-surface activity, and the lava dome in the N part of the crater continued to grow. Occasional plumes (described variously as white-to-medium gray, gray-to-gray black, and ash) rose to altitudes of 1.5-2.4 km (200-1,100 m above the summit crater).

Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were observed infrequently during the reporting period. Hotspots were observed on seven days in December 2015, but only 1-3 days per month for subsequent months through March 2017. No hotspots were recorded during December 2016 and February 2017. In contrast, the MIROVA detection system recorded numerous anomalies between April 2016 and March 2017 (figure 10), almost all of which were at least 1 km from the volcano and of low power output.

Figure 10. Thermal anomalies recorded at Ibu by the MIROVA system using MODIS infrared satellite data for the year ending 10 March 2017. Courtesy of MIROVA.

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/); 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/).

October 2017 (BGVN 42:10) Cite this Report

Occasional weak ash explosions and thermal anomalies during April-August 2017

During March 2014-March 2017, activity at Ibu consisted of lava-dome growth, occasional weak emissions containing ash (figure 11), and frequent thermal anomalies (BGVN 40:11 and 42:05). Ongoing activity between April and August 2017 consisted primarily of intermittent ash explosions. Data come from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC).

Figure 11. Photo of an ash explosion from Ibu's central vent in November 2014. Courtesy of Tom Pfeiffer, Volcano Discovery.

On 3 April 2017, at 0757 (local), an explosion produced an ash plume that rose to an altitude of 1.7 km and drifted S. Seismic signals indicated explosions and avalanches. During the rest of April through August, occasional explosions generated weak ash plumes that generally rose to altitudes of 1.5-1.8 km (0.2-0.5 km above the volcano) and drifted in various directions (table 2).

Table 2. Ash plume data for Ibu, April-August 2017. Courtesy of PVMBG and Darwin VAAC.

Between April and August 2017, thermal anomalies (based on MODIS satellite instruments analyzed using the MODVOLC algorithm) were recorded 2-5 days per month, with no monthly trend. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected numerous hotspots each month; all except one were within 3 km of the volcano, and all were of low or moderately-low power.

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/); 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/); 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/); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/).

May 2018 (BGVN 43:05) Cite this Report

Ongoing thermal anomalies from dome growth in the summit crater through April 2018

Ongoing activity at Ibu volcano from April through August 2017 consisted primarily of intermittent ash explosions (BGVN 42:10). Based on data and reports through April 2018, the eruption that began on 5 April 2008 appeared to be continuing. Monitoring of the volcano is the responsibility of the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Center for Volcanology and Geological Hazard Mitigation (CVGHM). Additional data below come from the Darwin Volcanic Ash Advisory Centre (VAAC) notices, with infrared MODIS data analyzed by the MODVOLC and MIROVA systems.

There were no reports of ash plumes from September 2017 through early March 2018. Although the summit area is often covered in fog, on 7-8 March ash plumes were observed rising 300-600 m above the crater rim and drifting W and S (table 3). Additional eruption plumes with ash were reported on 20 and 30 April. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2-3.5 km away from the active crater.

Table 3. Monthly summary of reported ash plumes and MODIS thermal anomalies from Ibu for August 2017-April 2018. The direction of drift for the ash plume through each month is highly variable. Data from Darwin VAAC, PVMBG, and MODVOLC.

Thermal anomalies identified by the MIROVA system using MODIS satellite data (figure 12) show that activity has been ongoing and almost continuous during May 2017-April 2018. Anomalies for the same time period detected and mapped using MODVOLC (figure 13, table 3) appear to be centered towards the north part of the crater and possibly extending down the N flank. This may indicate eruptive activity similar to that reported by PVMBG in June-December 2013 (BGVN 38:11) where the lava dome grew above the crater rim and sent incandescent material over a low notch in the rim and down a river valley towards Duono village, about 5 km NW.

Figure 12. Thermal anomalies at Ibu shown on a MIROVA plot (Log Radiative Power) for the year ending 3 May 2018. Courtesy of MIROVA.

Figure 13. A contour map showing MODVOLC thermal alert pixels at Ibu for the year ending 3 May 2018. Pixels are centered at the north crater rim and down the N flank. Courtesy of Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System.

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/); 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/).

December 2018 (BGVN 43:12) Cite this Report

Thermal anomalies and ash explosions from the crater continue during May-November 2018

Continuing activity at Ibu has consisted of numerous thermal anomalies and, except apparently for the period from September 2017 through early March 2018, intermittent ash explosions (BGVN 43:05). This activity continued through November 2018. The Alert Level has remained at 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side.

Ash plumes were seen frequently during May-November 2018 (table 4). Plume heights above the crater were generally 400-80 m. However, ash plumes on 28 and 29 July rose 5.5 and 4.8 km, respectively. Seismicity associated with ash plumes were characterized by explosion and avalanche signals.

Table 4. Ash explosions reported at Ibu, May-November 2018. Data courtesy of PVMBG and Darwin VAAC.

The number of thermal anomalies during this time, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, ranged from 2 days/month (July) to 9 days/month (September); some events were two pixels. Days with anomalies and ash explosions were not well correlated. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected numerous hotspots every month of the reporting period, almost all of which were within 5 km of the volcano and of low-to-moderate power. Infrared satellite imagery showed that the volcano had at least two, and sometimes three, active dome or vent locations (figure 14).

Figure 14. Sentinel-2 satellite images of Ibu on 19 August 2018. Top image (infrared, bands 12, 11, 8A) shows a large central hotspot and a smaller thermal area immediately to the west. Bottom image (natural color, bands 8, 4, 3) shows both an ash plume (gray) and steam plume (white), along with fresh and older lava in the crater. Courtesy of Sentinel Hub Playground.

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/); 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).

July 2019 (BGVN 44:07) Cite this Report

Frequent ash plumes and small lava flows active in the crater through June 2019

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.

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/).

January 2020 (BGVN 45:01) Cite this Report

Frequent ash plumes and small lava flows in the crater through December 2019

Heightened continuing activity at Ibu since March 2018 has been dominated by frequent ash explosions with weak ash plumes, and numerous thermal anomalies reflecting one or more weak lava flows (BGVN 43:05, 43:12, and 44:07). This report summarizes activity through December 2019, and is based on data from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC), and various satellites.

Typical ash plumes during the reporting period of July-December 2019 rose 800 m above the crater, with the highest reported to 1.4 km in early October (table 5). They were usually noted a few times each month. According to MAGMA Indonesia, explosive activity caused the Aviation Color Code to be raised to ORANGE (second highest of four) on 14, 22, and 31 August, 4 and 30 September, and 15 and 20 October.

Table 5. Ash plumes and other volcanic activity reported at Ibu during December 2018-December 2019. Plume heights are reported above the crater rim. Data courtesy of PVMBG and Darwin VAAC.

Thermal anomalies were sometimes noted by PVMBG, and were also frequently obvious in infrared satellite imagery suggesting lava flows and multiple active vents, as seen on 22 November 2019 (figure 19). Thermal anomalies using MODIS satellite instruments processed by the MODVOLC algorithm were recorded 2-4 days every month from July to December 2019. In contrast, the MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected numerous hotspots on most days (figure 20).

Figure 19. Example of thermal activity in the Ibu crater on 22 November 2019, along with a plume drifting SE. One or more vents in the crater are producing small lava flows, an observation common throughout the reporting period. Sentinel-2 false color (urban) images (bands 12, 11, 4), courtesy of Sentinel Hub Playground.

Figure 20. Thermal anomalies recorded at Ibu by the MIROVA system using MODIS infrared satellite data for the year 2019. Courtesy of MIROVA.

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/); 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/); 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).

July 2020 (BGVN 45:07) Cite this Report

Frequent ash emissions and summit incandescence; Strombolian explosions in March 2020

Ibu is an active stratovolcano located along the NW coast of Halmahera Island in Indonesia. Volcanism has recently been characterized by frequent ash explosions, ash plumes, and small lava flows within the crater throughout 2019 (BGVN 45:01). Activity continues, consisting of frequent white-and-gray emissions, ash explosions, ash plumes, and lava flows. This report updates activity through June 2020, using data from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC), and various satellites.

Volcanism during the entire reporting period dominantly consisted of white-and-gray emissions that rose 200-800 m above the summit drifting in multiple directions. The ash plume with the maximum altitude of 13.7 km altitude occurred on 16 May 2020. Sentinel-2 thermal satellite imagery detected multiple smaller hotspots within the crater throughout the reporting period.

Continuous ash emissions were reported on 6 February rising to 2.1 km altitude drifting E, accompanied by a hotspot visible in infrared satellite imagery. On 16 February, a ground observer reported an eruption that produced an ash plume rising 800 m above the summit drifting W, according to a Darwin VAAC notice. Ash plumes continued through the month, drifting in multiple directions and rising up to 2.1 km altitude. During 8-10 March, video footage captured multiple Strombolian explosions that ejected incandescent material and produced ash plumes from the summit (figures 21 and 22). Occasionally volcanic lightning was observed within the ash column, as recorded in video footage by Martin Rietze. This event was also documented by a Darwin VAAC notice, which stated that multiple ash emissions rose 2.1 km altitude drifting SE. PVMBG published a VONA notice on 10 March at 1044 reporting ash plumes rising 400 m above the summit. PVMBG and Darwin VAAC notices described intermittent eruptions on 26, 28, and 29 March, all of which produced ash plumes rising 300-800 m above the summit.

Figure 21. Strombolian explosions recorded at the crater summit of Ibu during 8-10 March 2020 ejected incandescent ejecta and a dense ash plume. Video footage copyright by Martin Rietze, used with permission.

Figure 22. Strombolian explosions recorded at the crater summit of Ibu during 8-10 March 2020 ejected incandescent ejecta and ash. Frequent volcanic lightning was also observed. Video footage copyright by Martin Rietze, used with permission.

A majority of days in April included white-and-gray emissions rising up to 800 m above the summit. A ground observer reported an eruption on 9 April, according to a Darwin VAAC report, and a hotspot was observed in HIMAWARI-8 satellite imagery. Minor eruptions were reported intermittently during mid-April and early to mid-May. On 12 May at 1052 a VONA from PVMBG reported an ash plume 800-1,100 m above the summit. A large short-lived eruption on 16 May produced an ash plume that rose to a maximum of 13.7 km altitude and drifted S, according to the Darwin VAAC report. By June, volcanism consisted predominantly of white-and-gray emissions rising 800 m above the summit, with an ash eruption on 15 June. This eruptive event resulted in an ash plume that rose 1.8 km altitude drifting WNW and was accompanied by a hotspot detected in HIMAWARI-8 satellite imagery, according to a Darwin VAAC notice.

The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected frequent hotspots during July 2019 through June 2020 (figure 23). In comparison, the MODVOLC thermal alerts recorded a total of 24 thermal signatures over the course of 19 different days between January and June. Many thermal signatures were captured as small thermal hotspots in Sentinel-2 thermal satellite imagery within the crater (figure 24).

Figure 23. Thermal anomalies recorded at Ibu from 2 July 2019 through June 2020 as recorded by the MIROVA system (Log Radiative Power) were frequent and consistent in power. Courtesy of MIROVA.

Figure 24. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) showed occasional thermal hotspots (bright orange) in the Ibu summit crater during January through June 2020. Courtesy of Sentinel Hub Playground.

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/); 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); Martin Rietze, Taubenstr. 1, D-82223 Eichenau, Germany (URL: https://mrietze.com/, https://www.youtube.com/channel/UC5LzAA_nyNWEUfpcUFOCpJw/videos, video at https://www.youtube.com/watch?v=qMkfT1e4HQQ).

January 2021 (BGVN 46:01) Cite this Report

Persistent daily ash emissions and thermal anomalies, July-December 2020

Mount Ibu is an active stratovolcano located along the NW coast of Halmahera Island in Indonesia. After a two-day eruption in 1911, Ibu was quiet until 1998-1999 when explosions produced ash emissions, a lava flow and dome growth began inside the summit crater. Although possible dome growth occurred in 2001 and 2004, little activity was reported until ash emissions began in April 2008. These were followed by thermal anomalies beginning the next month; ash emissions and dome growth have continued for 12 years and the dome now fills the summit crater (BGVN 45:07). Activity continued throughout 2020, consisting of frequent white-and-gray emissions, ash explosions, ash plumes, and small lava flows. This report updates activity through December 2020, using data from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC), and various satellite instruments.

Activity throughout July-December 2020 was very consistent and similar to activity reported earlier in the year. Tens of daily explosions produced white and gray ash emissions that rose 200-800 m above the summit (figure 25). Occasional larger explosions were reported in VONAs and VAAC notices. The MIROVA graph of log radiative power for the period shows consistent thermal anomalies the entire time (figure 26). Satellite imagery from Sentinel-2 identified thermal anomalies inside the summit crater every month, usually a larger central one and a smaller one to the NW, suggesting continued dome growth and lava flow activity (figure 27).

Figure 25. Between 60 and 90 explosions occurred most days at Ibu during 1 July-31 December 2020. White and gray plumes rose 200-800 m above the summit crater every day. Data courtesy of PVMBG daily reports.

Figure 26. The MIROVA graph of Log Radiative Power at Ibu from 3 February through December 2020 indicated a constant ongoing heat source from the summit of the crater. Courtesy of MIROVA.

Figure 27. Thermal anomalies persisted at the summit of Ibu throughout July-December 2020. One central anomaly was usual accompanied by a smaller one slightly NW of the central spot. Atmospheric penetration rendering (bands 12, 11a, and 8), courtesy of Sentinel Hub Playground.

The Darwin VAAC observed multiple minor ash emissions in satellite imagery drifting W on 6 July 2020 at 1.8 km altitude. A series of discrete puffs of ash were observed on 15 July also at 1.8 km altitude drifting W. Ongoing minor emissions were discernible on visible and RGB imagery at 2.1 km altitude drifting W on 20 July. On 30 July ash plumes rose to 1.8 km altitude drifted NW and a hotspot was present at the summit. A single MODVOLC alert was issued on 8 July. Single MODVOLC alerts were also issued on 11, 18, and 27 August 2020. PVMBG issued a VONA on 5 August, reporting an ash cloud that rose to 1.8 km altitude and drifted N (figure 28). The Darwin VAAC reported an ash emission later that day that rose to 4.3 km altitude and drifted NW for several hours before dissipating. Multiple discrete emissions were identified in satellite imagery drifting N at 2.1 km altitude on 11 August; they dissipated quickly. During 22-25 August intermittent ash emissions rose to 1.5-1.8 km altitude and drifted NW and W. Minor continuous emissions were again reported on 28 August.

Figure 28. Ash plumes rose from the summit of Ibu many days during July and August 2020, including on 8 July (top) and 5 August (bottom). Courtesy of PVMBG.

Many ash emissions during September and October 2020 were not accompanied by VONAs or VAAC advisories (figure 29). PVMBG issued a VONA on 20 September for an ash emission that rose to 1.5 km altitude and drifted N. Continuous discrete ash emissions over several days drifted SW to NW during 25-29 September at 1.8-2.1 km altitude, as reported in multiple VONAs and VAAC advisories. Single MODVOLC alerts were issued on 26 and 30 September. The Darwin VAAC issued an ash advisory on 8 October for intermittent ash emissions rising to 2.1 km altitude and drifting NW. A single MODVOLC alert was issued the next day. On 20 October ash emissions again rose to 2.1 km altitude and drifted NE.

Figure 29. Ash emissions at Ibu were photographed in webcams on 6 September (left) and 12 October (right) 2020. Courtesy of PVMBG.

The Darwin VAAC reported intermittent ash emissions to 1.8 km altitude during 3-5, 12-13, 18-19, and 22 November 2020 that drifted SSW for several hours before dissipating. PVMBG also issued a VONA for an ash cloud on 27 November that rose to 2.1 km altitude and drifted W. They reported faint rumbling at the PGA Ibu station on 10 November and loud rumbling on 16 and 18 November. During December, minor ash emissions rose to 1.8-2.1 km altitude and drifted E on 4 and 6 December, SW on 11 December, and SE on 12-13 December. PVMBG issued a VONA on 19 December for a white to gray ash cloud drifting N at 1.7 km altitude. Single MODVOLC alerts were issued on 10, 13, and 22 December. Numerous ash emissions were captured by the webcams (figure 30).

Figure 30. Ash emissions at Ibu were recorded in webcams on 17 November (top) and 5 December (bottom) 2020. Courtesy of PVMBG.

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/); 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).

September 2021 (BGVN 46:09) Cite this Report

Intermittent low-level ash plumes, light ashfall, and thermal anomalies during January-August 2021

Ibu is located along the NW coast of Halmahera Island in Indonesia and contains an inner crater measuring 1-km-wide and 400 m deep, an outer crater that measures 1.2-km-wide, and is breached on the N side. The first observed and recorded eruption occurred in 1911 and consisted of a small explosion in the summit crater. The current eruption period began in April 2008 and has recently been characterized by daily ash emissions, explosions, and thermal anomalies (BGVN 46:01). This report covers similar activity of white-and-gray emissions, ash plumes, and light ashfall during January through August 2021 using information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC), and various satellite data. The Volcano Alert Level remained at a 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater and 3.5 km away on the N side.

Activity throughout January-August 2021 was consistent and similar to that of the previous year. Between 35 and 115 daily explosions were detected during the reporting period, the latter of which occurred on 7 February, and produced white-and-gray emissions that rose 200-1,000 m above the crater and drifted in different directions, according to PVMBG. Occasional larger explosions were reported in VONA and VAAC notices. According to the MIROVA plot (Log Radiative Power), thermal activity was consistent, yet low in power from January through August; during May, the anomalies were at their lowest strength (figure 31). The MODVOLC algorithm detected ten thermal alerts during this period, with one each on 1 February, 9 March, 22 April, 2 and 27 June, 29 July, and 12 August, and three on 23 August 2021. Some of this thermal activity was detected in Sentinel-2 infrared satellite images on clear weather days (figure 32).

Figure 31. Constant low-power thermal anomalies were detected at the summit crater of Ibu during January through August 2021, as shown by the MIROVA graph (Log Radiative Power). Courtesy of MIROVA.

Figure 32. Thermal anomalies persisted in the summit crater of Ibu during January through August 2021. One strong central anomaly was commonly accompanied by a smaller one slightly to the NW, as shown on 10 January (top left), 1 March (top right), 5 April (middle left), and 8 August (bottom right) 2021. Images using “Atmospheric penetration” (bands 12, 11, 8A) rendering. Courtesy of Sentinel Hub Playground.

The Darwin VAAC detected a single minor ash plume on 7 January that rose to 1.8 km altitude, or about 500 m above the summit, and drifted N, based on a ground report. This information was also reported in a PVMBG VONA notice that stated the ash plume occurred at 1055. Similar low-level ash plumes persisted in February; during 5-6 February ash plumes rose to 1.8-2.4 km and drifted W and SW, based on HIMAWARI-8 satellite imagery. An ash plume rose 800 m above the crater on 8 February on 1101, according to a VONA notice. PVMBG reported that during 16-17 February a total of 88 eruptive events occurred. Consecutive ash plumes on 24, 25, and 26 February rose 500, 800, and 800 m above the crater, respectively (figure 33).

Figure 33. An ash plume rose from the summit of Ibu on 25 February 2021 to a height of 800 m. Courtesy of MAGMA Indonesia.

Similar intermittent ash emissions continued during March and April. On 3, 9, and 12 March an ash plume rose to 2.1 km and drifted S, according to Darwin VAAC notices (figure 34). During 14, 21, 25, and 31 March ash plumes rose 600-1,000 m above the crater, based on VONA notices and PVMBG daily reports. A thermal anomaly was detected in satellite imagery near the summit on 22 March and 6-7 April, according to a Darwin VAAC report. Accompanying the latter thermal anomaly, at 1812 a VONA notice reported an ash plume rose 400 m above the crater. An ash plume rose 800 m above the crater on 20 April at 1819 and another detected on 22 April at 1258 rose 1,000 m above the crater. On 26 April an ash plume rose 600 m above the crater and drifted N.

Figure 34. Intermittent ash plumes rising above the summit of Ibu were recorded multiple times in webcam images during March and April 2021, as shown here on 3 March 2021 rising to 2.1 km altitude and drifting S. Courtesy of MAGMA Indonesia.

During May and June, activity remained consistent with intermittent ash emissions. On 3 and 12 May an ash plume rose to 1.8 km altitude and drifted W and NW, based on HIMAWARI-8 satellite imagery. Ash plumes were visible during 16 (figure 35) and 17 May, the latter of which occurred at 1039 and rose ~750 m above the crater and drifted N. During the afternoon and evening of 19 May, light ashfall was reported in residential areas from the Naga village (4.8 km SW) to the Tongute village of Ternate (10 km W). On 6 and 10 June ash emissions rose to 1.8 km altitude and extended N. Rock avalanches were recorded through seismic data during 11-13 June, though they were not visually confirmed, according to PVMBG. During 18-20 June 63 eruptive events per day were detected.

Figure 35. Ash plumes from the summit of Ibu continued during May and June 2021, as seen here on 16 May 2021. Courtesy of MAGMA Indonesia.

Low ash emissions continued during July and August; on 10 July at 0719 an ash plume rose 800 m above the crater and the next day, light ashfall was reported in residential areas to the W of the volcano, though it was not specified how far. During 14-15 and 17 July white-and-gray emissions rose 200-800 m above the crater and drifted N, S, and W; light ashfall was again observed in residential areas to the W, and loud rumblings were heard as far as the Ibu observation post. On 28 July an ash plume rose to 2.4 km altitude and extended NE. During 1-2 August an ash plume rose to 1.8-2.1 km altitude. An ash plume on 18 August was reported at 0810 rising 800 m above the crater and drifting W. An ash plume on 22 August rose to 1.8 km altitude and was accompanied by a thermal anomaly that was identified in satellite imagery.

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.esdm.go.id/v1); 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/); 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).