Phreatic eruption on 21 July 2021

Sirung, located at the S end of Pantar Island, is truncated by a 2-km-wide caldera with a floor that often contains one or more small lakes. Fourteen eruptions have been documented since 1852, often with phreatic activity, including its most recent one that occurred during 7-8 July 2015; activity was characterized by a small, short-lived ash eruption (BGVN 41:02). This report updates information through September 2021 and includes a short eruption during July 2021, based on information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation) and the Darwin Volcanic Ash Advisory Center (VAAC).

No significant activity has been reported since an ash plume on 7 and 8 July 2015. Low seismicity was recorded during April through June 2021; a minor increase in tremor amplitude lasted 10 hours on 21 July, though there were no volcanic earthquakes indicative of magma movement. However, the Volcano Alert Level was raised to 2 (on a scale of 1-4) later that day. Following this increase in seismicity, a phreatic eruption was recorded at 1644 through 1800 on 21 July, which produced a white-and-gray ash plume that rose 2 km above the summit and drifted N (figure 1). Weak, intermittent, white gas-and-steam emissions continued to rise up to 500 m above the summit through August, according to PVMBG; some gas-and-steam emissions were noted during September.

Figure 1. Webcam image of the phreatic eruption at Sirung on 21 July 2021 that consisted of a white-and-gray ash plume. 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/).

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

December 1987 (SEAN 12:12) Cite this Report

Fumaroles and crater lake normal after earthquake

A VSI observer visited the volcano on 12 December. Fumaroles and the crater lake were normal and showed no evidence of increased activity that might be attributed to the M 6.5 earthquake of 26 November (preliminary epicenter 8.35°S, 124.25°E). The only notable change in the crater was a fresh landslide scar that may have resulted from the earthquake.

Information Contacts: VSI.

February 2016 (BGVN 41:02) Cite this Report

Small short-lived ash eruptions in May 2012 and July 2015

Small eruptions from Sirung were reported in May 2012 and July 2015. These were the first reported eruptions since 1970 from the volcano at the southern end of Pantar island, which sometimes has a crater lake and a history of phreatic activity.

Activity during 2012. The Indonesian Centre for Volcanology and Geological Hazard Mitigation (CVGHM) reported that on 8 May 2012 a three-hour long ash eruption that was accompanied by loud sounds and incandescence material that reached 10 m above the crater. An ash plume rose 3.5 km above the crater and drifted N, causing ashfall up to 4 mm thick near the crater. During 9-12 May white plumes rose 30-50 m above the crater.

On 12 May an ash plume rose to an altitude of 3 km and drifted about 95 km SW, and a sulfur odor was reported in areas up to 3 km away. That same day CVGHM raised the Alert Level to 3 (on a scale of 1-4) and recommended that visitors not approach the volcano within a 2.5 km radius. During 13-18 May 2012 diffuse white plumes rose 10-50 m above the crater. Seismicity was elevated during 12-17 May then decreased through 23 May, although levels remained above background. On 25 May the Alert Level was lowered to 2 (on a scale of 1-4).

CVGHM reported that during 1-13 June 2012 diffuse white plumes rose 30-70 m above the crater. A sulfur odor was occasionally noted at the Sirung observation post. Based on seismic activity and visual observations, on 15 June CVGHM reiterated that the Alert Level remained at 2 (on a scale of 1-4). On 7 September 2012 the Alert Level was lowered from 2 to 1 (on a scale of 1-4).

Activity during 2015. Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 7 July 2015 an ash plume from Sirung rose to an altitude of 1.5 km and drifted 85 km SW. On 8 July an ash plume at an altitude of 1.5 km drifted 55 km W.

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/).

October 2021 (BGVN 46:10) Cite this Report

Phreatic eruption on 21 July 2021

Sirung, located at the S end of Pantar Island, is truncated by a 2-km-wide caldera with a floor that often contains one or more small lakes. Fourteen eruptions have been documented since 1852, often with phreatic activity, including its most recent one that occurred during 7-8 July 2015; activity was characterized by a small, short-lived ash eruption (BGVN 41:02). This report updates information through September 2021 and includes a short eruption during July 2021, based on information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation) and the Darwin Volcanic Ash Advisory Center (VAAC).

No significant activity has been reported since an ash plume on 7 and 8 July 2015. Low seismicity was recorded during April through June 2021; a minor increase in tremor amplitude lasted 10 hours on 21 July, though there were no volcanic earthquakes indicative of magma movement. However, the Volcano Alert Level was raised to 2 (on a scale of 1-4) later that day. Following this increase in seismicity, a phreatic eruption was recorded at 1644 through 1800 on 21 July, which produced a white-and-gray ash plume that rose 2 km above the summit and drifted N (figure 1). Weak, intermittent, white gas-and-steam emissions continued to rise up to 500 m above the summit through August, according to PVMBG; some gas-and-steam emissions were noted during September.

Figure 1. Webcam image of the phreatic eruption at Sirung on 21 July 2021 that consisted of a white-and-gray ash plume. 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/).