Volcanos

Roundup of Global Volcanic Activity – New Activity for the week of 4 October - 10 October 2017

Agung | Bali (Indonesia) : On 5 October PVMBG reported that the rate of volcanic earthquakes at Agung had not increased during the previous 12 days, but continued to fluctuate at a high level. The seismic network detected 1-3 earthquakes per minute on average, with a total more than 600 events per day. The number of shallow volcanic earthquakes increased to 200 per day during 24 September-5 October, possibly indicating that magmatic activity at shallow depths was still high. The number of earthquakes felt by staff at the Mt. Agung Volcano Observatory in Rendang village, 12.5 km SSW, peaked on 27 September and then decreased afterwards. Gas plumes rose 50-200 m above the crater rim. Satellite data indicated an area of water expulsion near the solfatara field on the crater floor thought to reflect a disturbance to the hydrologic system in response to intruded magma at depth. On 5 October BNPB reported that the number of evacuees reached 146,797 (spread out in 427 shelters), though about 28 villages (70,000 people) were located within the evacuation zone. About 10,000 farm animals had also been evacuated. On 7 October a white plume likely composed mostly of water vapor rose 1.5 km above the crater rim and slowly drifted E. During 8-10 October fumarolic plumes rose 50-200 m above the rim. The Alert Level remained at 4 (the highest level on a scale of 1-4) with the exclusion zone at 9 km, and an additional expansion to 12 km in the SE, S, and SW directions.

Aoba | Vanuatu : Vanuatu Geohazards Observatory (VGO) stated that photographs and thermal infrared images taken on 30 September, and 1, 3, and 5 October during overflights of Aoba’s Lake Voui confirmed that the eruption was ongoing. Activity consisted of small explosions ejecting hot rock from vents on a new small island in the lake, and a small lava flow that traveled from the vent into the lake. On 6 October VGO noted that there was no evidence of the eruption escalating; the Alert Level was lowered to 3 (the middle level on a scale of 0-5) and residents and tourists were reminded to stay outside of the Red Zone defined as a 3 km radius around the active cone. Based on analyses of satellite imagery and model data, the Wellington VAAC reported that during 10-11 October ash plumes rose as high as 3.7 km (12,000 ft) a.s.l. and drifted N. On 11 October a news article stated that the government extended a state of emergency on the island to 24 October, delaying the return of the 11,000 residents that had been evacuated.

Lewotolo | Lomblen Island (Indonesia) : The number of shallow and deep volcanic earthquakes at Lewotolo recently increased, prompting PVMBG to raise the Alert Level from 1 to 2 (on a scale of 1-4) on 7 October. The report noted that the public should not enter the 2-km-radius exclusion zone around the crater. Solfatara emissions rose as high as 500 m above the crater rim on 9 October; emissions during 1 August-6 October rose 50-600 m. BNPB reported that five earthquakes recorded by Badan Meteorologi, Klimatologi, dan Geofisika (BMKG) on 10 October ranged in magnitude between 3.9 and 4.9, and were located 10-30 km below Lewotolo. The events were felt by local populations, causing an evacuation of 723 people. Preliminary data suggested that five homes were damaged from rock avalanches, triggered by the earthquakes.