Global Volcanism Program | Report on Lewotobi (Indonesia)

Report on Lewotobi (Indonesia) — 6 November-12 November 2024

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 6 November-12 November 2024
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2024. Report on Lewotobi (Indonesia) (Sennert, S, ed.). Weekly Volcanic Activity Report, 6 November-12 November 2024. Smithsonian Institution and US Geological Survey.

Weekly Report (6 November-12 November 2024)

Lewotobi

Indonesia

8.542°S, 122.775°E; summit elev. 1703 m

All times are local (unless otherwise noted)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Lewotobi Laki-laki remained at a high-level during 5-12 November, producing tall ash plumes, explosions, pyroclastic flows, and a lava flow, which all significantly affected residents, infrastructure, and transportation. The Badan Nasional Penanggulangan Bencana (BNPB) reported that as of 5 November there were 2,472 people spread across three evacuation shelters. A total of nine people had died (six from one family according to a news article) from the eruptive events that occurred during 3-4 November, 63 were injured, and five people remained in the hospital, one was critically injured. Information about damage to homes and infrastructure was incomplete because the exclusion zone and ongoing eruption prevented evaluations.

During 5-6 November dense gray ash plumes rose as high as 1 km above the summit and drifted SW, W, and NW. A webcam image from 1858 on 6 November showed incandescent material descending one of the flanks.

Another webcam image from 0244 on 7 November showed incandescent material being ejected above the summit and descending the flanks. Dense gray ash plumes during the early morning hours of the 7th rose as high as 2.5 km above the summit and drifted SW and W. At 0853 a dense gray ash plume rose 2.5 km above the summit and drifted SW. According to a news report the event was accompanied by a banging noise and pyroclastic flows that descended the NW flank about 1 km. PVMBG noted that during 1010-1200 dense ash plumes that were gray or gray and brown in color rose as high as 8 km above the summit and drifted SW. A news source reported that pyroclastic flows descended the NNE flank 3-4 km, and abundant amounts of ash fell from the plume onto the flanks and in areas downwind. Activities were prohibited within a radius of 7 km from the center of Laki-laki with restrictions expanding to 8 km on the SW and NW flanks later that afternoon. During 7-8 November the Darwin VAAC reported that some of the ash plumes rose as high as 16.8 km (55,000 ft) a.s.l. based on satellite data.

PVMBG and BNPB reported that several large explosive eruptions were recorded during 8-9 November, and BNPB noted that about 1,049 additional people evacuated from seven villages. At 0125 on 8 November an ash cloud rose 5 km above the summit and pyroclastic flows traveled as far as 3 km down the NE flank. Eruptive events at 0748, 1023, 1044, and 1314 generated ash plumes that rose 1-2.5 km above the summit. An explosive eruption at 1355 generated a dense ash plume that rose as high as 10 km and drifted SW, W, and NW. Pyroclastic flows descended the flanks in all directions and ash fell in areas downwind. According to a news report several “bangs” were heard by residents in Pululera Village (8 km NW), Wulanggitang. They observed dark black clouds accompanied by thunderstorms and occasional lightning; ash fell in the village 15-20 minutes after hearing the bangs. The hazard exclusion zone was expanded to an 8-km radius around both the Laki-laki and Perempuan craters and access to roads connecting East Flores and Sikka Regency was restricted. Authorities urged residents to go to centralized evacuation points in Wulanggitang and Larantuka Districts in the East Flores Regency, and in Maumere City (63 km WSW) in the Sikka Regency.

At 0447 on 9 November a dense, gray-brown ash plume rose 9 km above the summit and drifted SW, W, and NW. Rumbling sounds were reported. According to the Darwin VAAC the ash plumes rose as high as 15.2 km (50,000 ft) a.s.l. based on satellite data. Pyroclastic flows descended the NW flanks as far as 2 km. Intense incandescence emanating above the summit and avalanches of incandescent lava descended multiple flanks. Eruptive events at 0716, 0850, 1123, 1233, 1253, 1508, 1640, 1815, and 1942 on 9 November generated ash plumes that rose as high as 6 km above the summit. The VAAC reported that at 0850 and 0920 ash plumes rose as high as 15.8 km (52,000 ft) a.s.l. and drifted W.

During 0600-1200 on 9 November the hazard exclusion zone was expanded to 9 km on the SW, W, and NW flanks of Laki-laki. Additional evacuation centers opened in SDK Eputobi (16 km NNE) in the Titehena District. Community members were assisting in food preparation, health workers offered care and psychological support to families, teachers were providing lessons to students, and surrounding communities helped with sanitation needs. By 2000 on 9 November a total of 11,445 residents had evacuated. The Komodo Labuan Bajo Airport (317 km W) was closed during 9-10 November and at least 30 flights were cancelled. Ships were sent to transport people to areas with open airports.

According to a news report an eruption occurred early in the morning on 10 November; a photo showed streams on incandescent material covering the upper flanks. A webcam image captured at 1814 showed a possible lava flow on the upper W or NW flank. BNPB reported that on 10 November two evacuation posts, in Hikong and Kringa (12-15 km from the summit), that were being affected by ashfall were moved to East Flores. Ash plumes rose 1-6 km above the summit and drifted SW, W, NW, and N.

On 11 November airports that remained closed because of ashfall included the Komodo International Airport, the Francis Airport Xaverius Seda (60 km W), the H. Hasan Aroeboesman Airport (126 km WSW), the Soa Airport (190 km W), and Frans Xavier Seda Airport (252 km W). Ash plumes continued to be produced, rising 0.5-2.5 km above the summit and drifting SW, W, and NW. A webcam image at 2006 showed incandescent material being ejected above the summit, and advancement of the lava flow on the NW flank.

Ash plumes on 12 November rose as high as 9 km above the summit and drifted SW, W, and NW. Webcam images from 0406 and 0527 showed the advancing lava flow and a dark plume rising from possibly the end of the flow. A news report noted on 12 November that preliminary estimates suggested that around 2,700 housing units needed to be built for evacuees to be relocated. The H. Hasan Aroeboesman Airport, Gewayantana Airport (38 km NE), Frans Xavier Seda Airport, and Soa Airport in Bajawa among others remained closed. According to a news report about 84 flights in and out of Bali’s Gusti Ngurah Rai international airport (835 km W) were affected during the previous few days and on 13 November 90 international and domestic flights were cancelled. BNPB reported that by 13 November a total of 13,116 people were in evacuation shelters across eight locations.

Geological Summary. The Lewotobi edifice in eastern Flores Island is composed of the two adjacent Lewotobi Laki-laki and Lewotobi Perempuan stratovolcanoes (the "husband and wife"). Their summits are less than 2 km apart along a NW-SE line. The conical Laki-laki to the NW has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has had observed eruptions in 1921 and 1935. Small lava domes have grown during the 20th century in both of the summit craters, which are open to the north. A prominent cone, Iliwokar, occurs on the E flank of Perampuan.