Phreatic explosion on 29 April 2021

Infrequent phreatic explosions have occurred at the Sileri Crater Lake in the Dieng Volcanic Complex, with three explosions between 30 April and 2 July 2017, and one on 1 April 2018 (BGVN 42:10, 43:05). None were reported in 2019 and 2020. The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Centre for Volcanology and Geological Hazard Mitigation or CVGHM).

PVMBG reported that a phreatic explosion at the Sileri Crater Lake occurred at 1825 on 29 April 2021, ejecting rocks 200 m S and E and mud 400 m S and 300 m E. According to a news article, a local road was temporarily closed because rocks (about 10 cm in diameter) from the explosion were scattered along the road and the mud made conditions slippery. The closest residents are 1 km away. The Alert Level remained at 1 (on a scale of 1-4), and the public was warned to stay 500 m away from the crater rim.

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/); Detik News (URL: https://news.detik.com/).

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

February 1979 (SEAN 04:02) Cite this Report

Gas emission kills nearly 200

Gas containing CO₂ and H₂S was ejected from Sinila Crater at 0330 on 20 February, killing (at latest report) 182 persons and injuring about 1,000, over 100 of whom had to be hospitalized [but see 4:3]. A police colonel said that 17,000 people had been evacuated from six villages near Sinila. A number of livestock were also killed by the gas, and ponds near the crater were covered with dead fish.

An AP wirephoto showed bodies of some of the victims, who did not appear to be burned, nor were they covered with ash. Nearby vegetation also appeared burned. Many of the fatalities occurred in the village of Bandjarnegara, located in a valley on Dieng's SW flank.

The gas emission from Sinila was preceded by seven felt earthquakes and followed by ejection of "smoke." UPI reported that "lava continued to pour over the slopes of the Dieng Plateau" on 20 February. Sikidang Crater is located in the summit caldera, 27 km NE of Bandjarnegara, and is said to be 11 km from Sinila Crater.

Information Contacts: AFP; Jakarta DRS; Antara News Agency, Jakarta; AP; UPI; Reuters; S. Russell, USGS.

March 1979 (SEAN 04:03) Cite this Report

149 killed by poisonous gas during 20 February eruption

The following information is compiled largely from interviews with Subroto Modjo, Chief of the Geothermal Section, Indonesian Directorate of Volcanology.

Poisonous gas emission, accompanying a phreatic eruption from the SW portion of the Dieng volcanic complex, killed 149 persons early on 20 February. Nearby residents felt earthquakes at 0155, 0240, and 0400, after which an explosion at 0504 ejected a dark gray cloud from Sinila Crater (figure 1), a small, water filled pre-existing vent. Less than 1 hour later, after the ejection of a second dark gray cloud, a hot lahar from Sinila flowed down a gully, cutting a road. At 0650, a new crater, named Sigluduk, opened 250 m W of Sinila and began emitting vapor. Sinila produced a second, larger lahar a few minutes later. The total volume of Sinila's two lahars was about 15,000 m³.

Figure 1. Hazard zonation map showing the SW portion of the Dieng Volcanic Complex. Entry is prohibited to the first danger zone (dotted pattern); entry is permitted to the second danger zone (diagonal lines) only on sunny, windy days. Known gas vents are represented by circles; fatalities are marked by x's. Courtesy of Adjat Sudradjat, VSI.

Residents of Koputjukan village fled the activity in several directions. Many of those who headed W towards Batur were killed by gas containing CO₂ and H₂S, emitted from many small vents and fissures S and W of the two craters, ponded in a low-lying area beside the road. Others were killed near an elementary school, to which they had retreated after observing the deaths along the Koputjukan-Batur road. Both areas had been known to emit poisonous gases in the past. Four rescue workers were also killed. About 15,000 were evacuated from six nearby villages, and two danger zones were delineated around the gas vents (figure 1); entry into the inner zone was completely prohibited, and use of the outer zone was limited to daylight hours.

Activity from the two explosion craters declined after ejection of a dark gray cloud from Sigluduk at 1100 on 20 February. By dawn the next day, Sinila was emitting dense white vapor, but only a little white vapor was escaping from Sigluduk. VSI personnel visited the craters early on the 22nd. Sinila's vapor emission had ended, although the bottom of the crater, 60-70 m across and 40 m deep, was filled with bubbling mud. Sigluduk, 25 m in diameter and 10 m deep, contained an active solfatara with a temperature of 71°C.

Further Reference. Le Guern, F., Tazieff, H., and Faivre Pierret, R., 1982, An example of health hazard: people killed by gas during a phreatic eruption: Dieng Plateau, Java, Indonesia: BV, v. 45, p. 153-156.

Information Contacts: S. Modjo, VSI; M. Krafft, Cernay; Kompas and Sinar Harapan, Jakarta.

December 1981 (SEAN 06:12) Cite this Report

Earthquake swarm, but little change in thermal activity

On 17 November an area of the Dieng volcanic complex with a history of poisonous gas emission experienced an MM 2-3 felt earthquake. A tripartite electromagnetic seismometer located the shocks in a zone of fractures and gas emission 1-2 km E of Batur. Newspapers and radio broadcasts reported that 3-12 seismic events were recorded during each of the 10 days ending 6 December. However, the number of events began to decrease in early December, and seismicity was continuing to decline as of the 17th.

There were no indications of volcanic activity. The poisonous gas content of vapor sampled at several known emission sites had not changed more than 15% from previous measurements. The temperature of the pool of boiling mud at Sileri cone and the thermal feature Sikidang, a few kilometers E of the zone, remained unchanged at 90°C. Government officials issued an alert, but removed it after receiving a VSI report.

Information Contacts: A. Sudradjat, VSI; Jakarta DRS.

April 1986 (SEAN 11:04) Cite this Report

Earthquakes and tremor but no change in thermal activity

"A widely-felt earthquake occurred near Dieng on 13 April at 0747. Tremor was recorded for up to 10 minutes 14-15 April. Additional small earthquakes were recorded in the following two weeks. No changes were noted in thermal activity."

Information Contacts: Olas, Suratman, Suparto, Kaswanda, and A. Sudradjat, VSI.

August 1986 (BVE 26)

Phreatic explosions on August 6

[Phreatic eruptions took place on 6 August 1986 from the Sileri crater lake. The height of mud ejection was not observed, but the crater was covered by thick white smoke that rose ~300 m high. After a few hours the spout was ~6-7 m high and was gradually decreasing.]

Information Contacts: S. Siswowidjoyo and W. Modjo, VSI (as reported in BVE, no. 26, March 1989).

April 1992 (BGVN 17:04) Cite this Report

Sudden gas emission kills one person and hospitalizes two others

A sudden gas emission occurred at about 1600 on 18 March from a fractured and altered zone in a river valley 200 m W of Sikidang Crater. After the gas emission, one person was found dead in the stream, and two others were hospitalized after trying to rescue him. Surface gas measurements the next day indicated high concentrations of CO₂ and O₂ (40 and 15 weight %, respectively), and lesser concentrations of H₂S and HCN (200 and 197 ppm, respectively).

Steam emission continued from Sileri Crater (~3 km NNW of Sikidang), rising 40-60 m in mid-April. An average of one A-type and seven B-type volcanic earthquakes were recorded daily during mid-April, an increase from earlier in the month.

Information Contacts: W. Modjo, VSI; T. Casadevall, USGS.

January 1993 (BGVN 18:01) Cite this Report

Hot mud fountains and steam emissions; poisonous gas

Hot mud began fountaining from a new vent (near the Pandawa Lima Temples) area at 0001 on 23 January. The fountaining was heard by residents of a nearby village (Bale Kambang). The hot mud, which emerged from a 5-m-diameter hole, had a temperature of 93°C and reached heights of 2-15 m. Hot mud and steam emissions were continuing on 8 February, with fountaining to 1 m height. The area within 25 m of the hole has been covered with mud. Gas measurements taken on 8 February detected 15 ppm HCN and 12 ppm H₂S. Shallow volcanic earthquakes were recorded in January at rates of 3-20/day, but were decreasing prior to the 23 January activity. Seismicity has continued since then.

Information Contacts: W. Tjetjep, VSI.

August 1998 (BGVN 23:08) Cite this Report

Plumes and earthquakes in early July

Seismicity increased in late June and early July. Earthquakes of M ~2 were felt locally three times on 2 July, and once on 4 July. An emission plume of white, moderately thick steam without ash issued from Sileri crater under low pressure to a height of 50 m. There was a moderate smell of sulfur. The crater lake water was clear to gray in color with temperatures varying between 54 and 94°C.

Information Contacts: R. Sukhyar, Director, Volcanological Survey of Indonesia (VSI), Bandung, Indonesia (URL: http://www.vsi.esdm.go.id/).

May 2002 (BGVN 27:05) Cite this Report

Increase in seismicity and plume emission beginning in April 2002

The last reported activity at Dieng occurred during late June and early July 1998, when three M ~2 earthquakes were felt and a white steam plume was emitted from Sileri crater to a height of 50 m (BGVN 23:08). During April 2002, the Volcanological Survey of Indonesia (VSI) reported that activity at Dieng increased. Beginning on 19 April the number of deep and shallow volcanic earthquakes increased (table 1), and a white plume of variable thickness rose 25-50 m above Sileri crater. The temperatures of fumaroles in various craters were 50-95°C (table 2). Dieng remained at Alert Level 2 through at least 26 May 2002.

Table 1. Earthquakes recorded at Dieng during 15 April through 19 May 2002. Courtesy VSI.

Table 2. Temperatures of various craters of Dieng during 15 April through 12 May 2002. "--" indicates that the information was not reported. Courtesy VSI.

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

June 2003 (BGVN 28:06) Cite this Report

Plume emissions and modest seismicity through early July 2002

Seismicity and plume frequency increased at Dieng beginning in April 2002 (BGVN 27:05). During 27 May-7 July 2002, the Volcanological Survey of Indonesia (VSI) reported higher-than-normal activity. Deep and shallow earthquakes were recorded, along with tectonic events (table 3). During 27 May-9 June, VSI reported a white plume from Sileri crater up to 50 m high. Observations in mid-June revealed a mud ejection from Sikidang crater. Dieng remained at Alert Level 2 (on a scale of 1-4). No further reports were issued through at least May 2003.

Table 3. Earthquakes recorded at Dieng during 27 May-7 July 2002. Courtesy VSI.

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

July 2003 (BGVN 28:07) Cite this Report

Mud bubbling and outflows at Sileri crater that reached 50 m beyond crater rim

According to the Volcanological Survey of Indonesia (VSI), on 20 July 2003 mud poured from Sileri crater. The crater contains a lake and boiling mud pots, and has been the site of small-to-moderate historical eruptions. The incident of 20 July occurred at night and sent mud as far as 25 m S of the crater rim. On 21 July, a temperature measurement of the crater recorded 74°C, no striking increase from earlier measurements.

On the morning of 24 July, another mud outpouring from the crater covered an area up to 50 m N and E of the crater rim. Activity then continued with small areas of mud bubbling and ejecta thrown 1 m high at the middle of the crater. Neither of the mud-outpouring events were recorded on the seismometer 1.1 km S of the crater. The volcano's hazard status was raised to level 2 on 22 July.

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

September 2003 (BGVN 28:09) Cite this Report

One shallow volcanic earthquake and a gas plume in early August

The Volcanological Survey of Indonesia (VSI) activity report for the week of 4-10 August 2003 noted, for the Sileri crater in the Dieng volcano complex, one shallow volcanic earthquake, a white gas plume rising 25-60 m, and water temperature of 83°C. The hazard status was set at Alert Level 2 (on a scale of 1-4).

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

April 2009 (BGVN 34:04) Cite this Report

Landslide triggers sudden, small, phreatic eruption on 15 January 2009

This report discusses a small phreatic eruption at Dieng from Sibanteng crater in January 2009. The Dieng complex covers more than 80 km² in Central Java NW of Yogyakarta. The volcanic field trends E and contains two or more stratovolcanoes, more than 20 craters and cones, several crater lakes, a caldera, and active thermal features (van Bergen and others, 2000). Phreatic eruptions are those that eject both magmatic gasses and steam, and contain fragments of pre-existing solid rock from the volcanic conduit or vent, but without primary erupted magma. Many of these eruptions are attributed to subsurface interaction between magma and groundwater (Germanovich and Lowell, 1995). Some are precursors to phreatomagmatic and magmatic eruptions.

Recent reports discussed mud ejected from the active Sileri crater in July 2003 associated with a modest increase in seismicity and steam plumes during April-July 2002 and August 2003 (BGVN 27:05, 28:06, 28:07, and 28:09). A May 2005 pilot report of a steam plume turned out to be caused by pipe maintenance at Dieng's geothermal site.

January 2009 landslide and eruption. This event began when, after three days of heavy rain, one or more landslides broke loose in steep volcanic terrain at about the 1900- to 2000-m elevation at 0800 on 15 January 2009. Landslide debris covered the floor of Sibanteng crater, sealing the vent there. At 0830 a sudden and short-lived phreatic eruption took place. The alert level was raised to 2 (on a scale of 1 to 4).

Much of these and other details were learned by an emergency response team from the Center of Volcanology and Geological Hazard Mitigation (CVGHM), who conducted a field investigation between 16-21 January. The team's findings are discussed below (as extracted from the CVGHM report dated 22 January 2009 ("Tanggap Darurat G. Dieng Kab. Wonosobo, Prov. Jawa Tengah, tanggal 16-21 Januari 2009").

The eruption left an explosion crater about 50 m in diameter and deposited the bulk of the erupted material in a ~ 50 m radius. The erupted deposits consisted of material from the landslide and vent area. This relationship indicated that the landslide preceded the phreatic eruption. The landslides covered an area 100 x 200 m, with an estimated 40,000 m³ of debris. In places, the landslide debris created temporary dams. One blocked the Kali Putih River, and downstream, the Kali Tulis River.

On 17 January, four additional seismic stations were installed. Three were in the vicinity of the Sibanteng and Sikidang craters and one was near the thermally active colored lake Telaga Warna. Earthquakes and tremor were both absent on the seismographic record at Timbang crater during 17-20 January following the phreatic eruption.

The team reported that witnesses in the field had heard two explosions. The first came from the landslide; the second, the phreatic eruption. During their visit, the eruption vent emitted a white plume 5 m high. The vent was largely covered by landslide debris from Sibanteng crater's upper wall. In Sibanteng and other craters temperature ranges were 93.2-93.6° C, values similar to previous data.

The concentrations of gases, including hydrogen sulfide (H₂S), sulfur dioxide (SO₂), methane (CH4), carbon dioxide (CO₂), and carbon monoxide (CO) were reported for eight locations. The CO and CO₂ concentrations were below ~ 1 ppm. H₂S concentrations were under ~ 7 ppm, with the highest value seen near a thermal feature at Skikdang, but a 6 ppm value near a bulletin board in a tourist area. The eight SO₂ concentrations were under 18 ppm. CH4 concentrations ranged between 5 and 17 ppm. (More detailed data are available in the 22 January CVGHM report.)

The investigation indicated that the phreatic eruption was preceded by one or more landslides that covered the floor of Sibanteng crater. The team suggested that the sealing action and pressure buildup due to the landslide caused the phreatic eruption. They concluded that the phreatic eruption posed no danger to the public because the Sibanteng crater is not close to an inhabited area. However, they noted that landslide debris was still unstable and could be easily dislodged and transported by rainwater.

Reference. Germanovich, L.N., and Lowell, R.P., 1995, The mechanism of phreatic eruptions: J. Geophys. Res., v. 100 (B5), p. 8417-8434.

van Bergen, M.J., Bernard, A., Sumarti, S., Sriwana, T., and Sitorus, K., 2000, Crater lakes of Java: Dieng, Kelud and Ijen, Excursion Guidebook, IAVCEI General Assembly, Bali 2000 (URL: www.ulb.ac.be/sciences/cvl/DKIPART1.pdf).

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

August 2009 (BGVN 34:08) Cite this Report

Seismicity before a 26 September 2009 phreatic eruption

This report describes a phreatic eruption at Dieng on 26 September, an event preceded by increased seismicity. Previously, a phreatic eruption on 15 January 2009 followed the burial and sealing of the floor of the Sibanteng crater by landslides (BGVN 34:04). In the past, a large number of eruptions from the Dieng complex have been minor phreatic events (Germanovich and Lowell, 1995; van Bergen and others, 2000). Monitoring is carried out by the Center for Volcanology and Mitigation of Geologic Disasters (CVGHM) from the village of Karang Tengah.

Seismic activity within the complex began in early September 2009. Four deep volcanic and two shallow volcanic earthquakes preceded a phreatic eruption on 26 September. On that day CVGHM reported a thunderous noise from Dieng heard up to 2 km away. The next day, a phreatic eruption from an unspecified crater ejected mud as far away as 140 m S. The deposits were as thick as 10 cm near the vent and 1 cm near the farthest point of deposition. Scientists did not observe an increase in the concentration of poisonous gases at either the vent or in the surrounding area.

Reference. Germanovich, L.N., and Lowell, R.P., 1995, The mechanism of phreatic eruptions: J. Geophys. Res., v. 100 (B5), p. 8417-8434.

van Bergen, M.J., Bernard, A., Sumarti, S., Sriwana, T., and Sitorus, K., 2000, Crater lakes of Java: Dieng, Kelud and Ijen, Excursion Guidebook, IAVCEI General Assembly, Bali 2000 (URL: www.ulb.ac.be/sciences/cvl/DKIPART1.pdf).

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

June 2011 (BGVN 36:06) Cite this Report

Seismicity and dangerous gas emissions; 1,200 evacuate in May-June 2011

This report on Dieng volcanic complex (figure 2) notes both toxic gas emissions and episodes of high seismicity during 1 October 2009-July 2011. A late May 2011 visit, after increased gas emissions were noted the previous week, revealed dead birds and damaged vegetation at Timbang crater. Gas measurements at several sites confirmed the presence of hazardous gases; however, there were no human fatalities or injuries noted. According to news reports, 1,200 people were evacuated. Our previous report on Dieng discussed a phreatic eruption on 26 September 2009, preceded by a series of volcanic earthquakes (BGVN 34:08).

Figure 2. A sketch map for Dieng Volcanic Complex, which lies in Central Java associated with the ~2-km-high plateau of the same name. The Dieng plateau is E-trending and roughly 14 by 6 km. Taken from Van Bergen and others (2000).

During January 2010, landslides took place near Dieng, followed by others at distance. One landslide crossed the highway between Dieng and Wonosobo (the regional capital, 18 km S of Dieng). The second landslide struck a village called Wonoaji, and according to a Jakarta Post article (by Suherdjoko, 21 January 2010), "Two people [there] have died and three are still missing, while five others were injured. . . ."

Although little was reported regarding Dieng during October 2009-2010, Relief Web posted a graphic describing heavy rains and regional flooding during February 2010 in the portion of Central Java hundreds of kilometers E of Dieng near Bandung. This episode triggered a landslide in Ciwidey village taking 17 lives.

The latest reported activity at Dieng began in mid-2011. According to the Center of Volcanology and Geological Hazard Mitigation (CVGHM), seismicity at Dieng increased during 18-22 May 2011. On 22 May, diffuse white plumes rose from the Timbang cone; plumes from the cone had not been previously observed. The next day carbon dioxide (CO₂) emissions increased. On 23 May, CVGHM raised the Alert Level to 2 (on a scale of 1-4).

CVGHM reported that on 29 May 2011, gas plumes rose 50 m above Timbang cone. The gas plumes drifted S through the valley. Observers who visited the cone noted the previously mentioned damaged vegetation and dead birds. Seismicity and CO₂ emissions remained elevated, thus prompting CVGHM to raise the Alert Level to 3.

During 4-5 June white plumes from Sileri crater rose 20-60 m and white plumes from Timbang rose only 2 m and drifted 300 m S. Seismicity and carbon dioxide remained high through 5 June

According to CVGHM, carbon-dioxide emissions from Timbang declined during 31 May-10 June, while seismicity decreased during 5-7 June and was not detected during 8-10 June. White plumes were not observed. On 10 June the Alert Level was lowered to 2.

Stated gas concentrations. In early June, low levels of hydrogen sulfide (H₂S, 0.002-0.05% by volume) were recorded at Sikendang, Sikidang, Sibanteng, and Sileri craters. Carbon monoxide gas (CO) was only detected along the steam vents of Sikendang crater, at a concentration of 0.004% by volume. CO₂ was measured at a concentration of 5.0% by volume. On 5 June, the CO₂ from Timbang was at its highest level at, 1.54% by volume. The scientists added that weather patterns had brought low atmospheric pressure, which had enhanced gas escape at the vent.

John Seach presents modest-resolution photos from 2010 showing the Sikidang vent mentioned above, and Telega Warna crater lake (see Information Contacts).

Figure 3 shows one approach to communicating gas-hazards warnings.

Figure 3. A sign written in Indonesian warning people crossing a part of the Dieng complex susceptible to dangerous gas emissions. The sign states, "Caution—Contaminated Area—Poisonous Gases." This photo appeared in an article published 5 June 2011 in the news source ANTARA/Anis Efizudin.

Dieng plateau. In the modern record, Dieng has a history of lethal gas emissions, phreatic explosions, and other hazards. The complex contains rocks ranging from andesite to rhyodacite, extrusives filling and sitting upon a large older (Pleistocene) caldera. It contains several stratovolcanoes, and many cones, craters, domes, and thermal features (see subsections below).

Van Bergen and others (2000) described the plateau and associated volcanic complex, portions of which follow.

"The Dieng Volcanic Complex in Central Java is situated on a highland plateau at about 2000 m above sea level, approximately 25 km N of the city of Wonosobo. It belongs to a series of Quaternary volcanoes, which includes the historically active Sumbing and Sundoro volcanoes. The plateau is a rich agricultural area for potatoes, cabbages, tomatoes and other vegetables. There are numerous surface manifestations of hydrothermal activity, including lakes, fumaroles/solfatara and hotsprings. The area is also known for the development of geothermal resources and lethal outbursts of gas. Scattered temples are the witnesses of the ancient Hindu culture that once reigned.

"In terms of chemical composition, Telaga Warna is the most interesting crater lake in the Dieng area. The original shape of the crater has been modified by a lava flow. The water occupies less than 1 km². Gas bubbles can be seen rising to the lake surface, and the air has a sulfurous odor. Its colorful appearance (warna stands for color(s) in Indonesian) makes the lake an interesting tourist attraction. The water has a pH of about 3, which may fluctuate depending on seasonal variations. Sulfate and chloride contents are moderately high. . . . Strong emissions of CO₂-rich gas on-shore have occasionally killed animals, so that a path on the N side used to be closed to avoid risks for local villagers."

The same report presents some composition data from 1994. Some of the 'dry' gas from several vents in the complex were up to 90% CO₂.

Geothermal energy. According to Geo Dip Energi, the Dieng #1 project is currently in operation and producing 60 MegaWatts (MW) of energy. Two more projects, each of 60 MW are underway. The Dieng area is thought to have more potential and could produce 300 MW.

Reference. Van Bergen, M., Bernard, A., Sumarti, S., Sriwana, T., and Sitorus, K., 2000. Crater Lakes of Java: Dieng, Kelud, and Ijen. Excursion Guidebook, IAVCEI General Assembly, Bali 2000, 9 pp. URL: http://www.ulb.ac.be/sciences/cvl/DKIPART1.pdf).

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Geo Dipa Energi, Recapital Building 8th Floor, Jl. Aditiawarman Kav. 55 Jakarta Selatan 12160 Indonesia (URL: http://www.geodipa.co.id); John Seach, Volcano Live (URL: http://volcanolive.com); Xinhua News (URL: http://www.xinhuanet.com/english2010/); Jakarta Globe (URL: http://www.thejakartaglobe.com/home/).

August 2013 (BGVN 38:08) Cite this Report

Alert Level raised due to gas emissions; moderate earthquake felt

The Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that during 7-11 March 2013 instruments monitoring the Dieng Volcanic Complex detected carbon dioxide (CO₂) plumes from Timbang Crater, a cone that is part of the Dieng Volcanic Complex (see figure 2 in BGVN 36:06), drifting 50-200 m S. A strong sulfur odor was also reported, along with dead animals near the crater on 7 March. Observers noted white plumes rising from the crater that were diffuse during 7-8 March and dense during 9-10 March; the concentration increased during 9-10 March 2013. Because of the increase of CO₂ emissions, CVGHM raised the Alert Status, which spans a scale of 1 to 4, from 1 (aktif - normal) to 2 (waspada - alert) on 13 March, and warned the public not to approach Timbang Crater within a 500 m radius. The last eruption reported from Dieng was 27 September 2009 at Sileri crater (BGVN 34:08; see figure 2 in BGVN 36:06). Table 4 shows the most recent Alert Levels for Dieng.

Table 4. Most recent Alert Levels reported for Dieng. Courtesy of CVGHM.

During 10-26 March 2013 gas emissions continued to be elevated at Timbang crater. Plumes containing CO₂ and hydrogen sulfide (H₂S) drifted 2 km, and were at toxic levels at a distance of 550 m. Seismicity increased during 13-26 March 2013 and then significantly increased on 27 March. CVGHM raised the Alert Level to 3 (siaga - standby) on 27 March 2013 and warned the public not to approach Timbang Crater within a 1 km radius.

On 28 March 2013 gas emissions continued to raise at Timbang. Plumes containing carbon dioxide (CO₂) drifted 2 km towards the S valley of Kali Sat, prompting a road closure until the early evening when the gas concentration decreased. On 30 March 2013 CO₂ gas emissions were not detected; however, 'smoke' rose at most 100 m above the crater, and hydrogen sulfide (H₂S) odors were very potent in areas 1 km W and weak in areas 1.5 km S.

On 24 March 2013 Sileri Crater lake water changed from dark gray to brown, and on 7 April white plumes rose 50 m and the water color returned to normal. Diffuse white plumes rose 15 m on 20 April. Other craters had not exhibited any changes by 28 April 2013.

On 19 April sulfur dioxide (SO₂) odors were reported. According to CVGHM, an M 4.8 earthquake occurred ~14 km SSW of Dieng and ~8 km NNW of Wonosobo at 1900 local time on 19 April 2013. It had a hypocentral depth of 10 km, was of a tectonic nature, but with possible influence on Dieng volcano. Eighty-six weaker quakes followed the main shock within 25 minutes. No buildings collapsed due to the earthquake, but at least 311 houses were damaged, 34 of them severely and 27 of them moderately. Two people were injured. As a precaution associated with a potential eruption, approximately 1,000 people were evacuated; they were returning to their villages by 21 April due to a decrease in volcanic activity of the Dieng volcano complex.

Based on gas concentrations, seismicity, and visual observations, CVGHM lowered the Alert Level to 2 on 8 May 2013.

Residents living in the vicinity of Dieng (close to Mt. Sundoro and Mt. Sumbing) on Java (see figure 1 in BGVN 33:11), were the subject of a study of people's perceptions and reactions to volcanic hazards (Lavigne and others, 2008).

Reference: Lavigne, F., De Coster, B., Juvin, N., Flohic, F., Gaillard, J-C., Texier, P., Morin, J., and Sartohadi, J., 2008, People's behaviour in the face of volcanic hazards: Perspectives from Javanese communities, Indonesia, Journal of Volcanology and Geothermal Research, v.172, issue 3-4, p. 273-287.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM) (Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG)), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/).

October 2017 (BGVN 42:10) Cite this Report

Three phreatic eruptions at Sileri Crater; deaths due to helicopter crash involved in evacuations

Located on an elevated plateau in central Java NW of Yogyakarta (figure 4), multiple craters within the Dieng Volcanic Complex (figure 5) have been intermittently active over the past 200 years. Brief phreatic eruptions took place at Sibanteng crater on 15 January 2009 (BGVN 34:04) and at Sileri crater on 26 September later that year (BGVN 34:08). Increased unrest during March-April 2013 (BGVN 38:08) consisted of elevated volcanic gas emissions from Timbang Crater that resulted in an increase in the Alert Level to as high as 3 on 27 March, then back to Level 2 on 8 May. There was a precautionary evacuation of local villages, but no eruption took place. Regular monitoring is done by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Centre for Volcanology and Geological Hazard Mitigation or CVGHM).

Figure 4. Topographic terrain map of central Java showing the Dieng Volcanic Province to the NW of Gunung Sumbing and Gunung Sindoro volcanoes. The volcano indicated by a red symbol N of Yogyakarta is Merapi. Courtesy of Peakery.

Figure 5. Topographic terrain map of the Dieng Volcanic Province on the Dieng plateau of central Java. The notable cone at bottom center is Bisma; the crater with a lake at center is Merdada, adjoining Kawah Sikidang to the SE. The frequently active Sileri area is immediately W of the more noticeable Pagerkandang crater N of Merdada. Courtesy of Peakery.

The alert status remained at Level 2 for about 15 months following the hazardous gas emissions in 2013. On 11 August 2014 the PVMBG noted that, due to decreased activity and no observable flow of gas in high concentrations from the crater, the Alert Level was lowered to 1 (on a scale of 1-4). No further activity was reported until late April 2017.

A phreatic event from Sileri Crater at 1303 on 30 April 2017 ejected material 10 m high and 1 m past the crater edge, forming a 1-2 mm thick deposit. Another emission at 0941 on 24 May consisted of gas and black "smoke" that rose 20 m.

The Disaster Management Authority, Badan Nacional Penanggulangan Bencana (BNPB), reported that there had been another phreatic eruption from the Sileri Crater lake at 1154 on 2 July 2017, ejecting mud and material 150 m high, and 50 m to the N and S. The event injured 11 of 18 tourists that were near the crater. According to a news article a helicopter on the way to assist with evacuations after the event crashed, killing all eight people (four crewmen and four rescuers) on board. PVMBG scientists visited the next day and observed weak white emissions rising 60 m.

PVMBG reported that during 8 July-14 September 2017 measurements indicated an increase in water temperature at Sileri Crater lake from 90.7 to 93.5°C. Soil temperatures also increased, from 58.6 to 69.4°C. At Timbang Crater temperatures in the lake increased from 57.3 to 62.7°C, and in the soil they decreased from 18.6 to 17.2°C. The report noted that conditions at Timbang Crater were normal.

Temperature increases at Sileri, along with tremor detected during 13-14 September, prompted PVMBG to raise the Alert Level to 2 (on a scale of 1-4). PVMBG warned the public to stay at least 1 km away from the crater rim, and for residents living within that radius to evacuate. However, after 20 September tremor and water temperatures both declined. The Alert Level was lowered back to 1 on 2 October, with a warning to stay at least 100 m from the crater rim.

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/); Peakery (URL: https://peakery.com/).

May 2018 (BGVN 43:05) Cite this Report

Phreatic explosion on 1 April 2018 at Sileri Crater

Dieng has had a history of intermittent phreatic explosions. In 2017, explosions occurred on 30 April, 24 May, and 2 July (BGVN 42:10). Another phreatic explosion occurred on 1 April 2018. The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Centre for Volcanology and Geological Hazard Mitigation or CVGHM).

PVMBG reported that a phreatic explosion at the Sileri Crater lake (Dieng Volcanic Complex) occurred at 1342 on 1 April 2018, ejecting mud and material 150 m high, and up to 200 m in multiple directions. The event was preceded by black emissions that rose 90 m, and then diffuse white emissions that rose 150 m. The report noted that few tourists were in the area due to rainy weather; visitors are not permitted within 200 m of the crater rim.

According to a news report (The Jakarta Post) that cited an official of the National Disaster Management Agency (BNPB), no toxic gases such as carbon dioxide, hydrogen sulfide, or sulfur dioxide were detected in the explosion.

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/); The Jakara Post (URL: http://www.thejakartapost.com).

May 2021 (BGVN 46:05) Cite this Report

Phreatic explosion on 29 April 2021

Infrequent phreatic explosions have occurred at the Sileri Crater Lake in the Dieng Volcanic Complex, with three explosions between 30 April and 2 July 2017, and one on 1 April 2018 (BGVN 42:10, 43:05). None were reported in 2019 and 2020. The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Centre for Volcanology and Geological Hazard Mitigation or CVGHM).

PVMBG reported that a phreatic explosion at the Sileri Crater Lake occurred at 1825 on 29 April 2021, ejecting rocks 200 m S and E and mud 400 m S and 300 m E. According to a news article, a local road was temporarily closed because rocks (about 10 cm in diameter) from the explosion were scattered along the road and the mud made conditions slippery. The closest residents are 1 km away. The Alert Level remained at 1 (on a scale of 1-4), and the public was warned to stay 500 m away from the crater rim.

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/); Detik News (URL: https://news.detik.com/).