Volcanos

Roundup of Global Volcanic Activity – New Activity for the week of 27 June – 3 July 2018

Agung | Bali (Indonesia) : PVMBG reported that seismicity at Agung continued to be dominated by low-frequency events. The number of earthquakes increased from 15/day on 25 June to 69/day on 28 June; harmonic tremor emerged on 27 June, and at 2221 an event generated an ash plume that rose 2 km above the crater rim and drifted W. Gas-and-ash emissions were continuous during 28-29 June, rising around 2 km and drifting W and SW, and incandescence was reflected in the plume; satellite data confirmed that high-temperature (1,200 degrees Celsius) lava flowed onto the crater floor. The intensity of the thermal anomaly on 29 June was the largest recorded at Agung since the beginning of the eruption on 21 November 2017.

BNPB noted that the ash plumes on 28 June caused some airlines to cancel flights to Bali, and ashfall was reported in several villages on Bangli. The International Gusti Ngurah Rai (IGNR) airport (60 km SW) in Denpasar, the Blimbing Sari Airport (128 km W) in Banyuwangi, and the Noto Hadinegoro Airport (200 km W) in Jember closed for portions of the day on 29 June.

Lava continued to effuse, and by 1 July the estimated volume of new lava was 4-5 million cubic meters making the total volume erupted since 21 November 2017 around 27-28 million cubic meters (50% of the total crater volume). The height difference between the lowest part of the crater rim (SW side) and the highest part of the lava surface (in the center of the crater) was 85-90 m. Satellite data showed that the intensity of the thermal anomaly decreased during 28 June-2 July, though still remained at a high level. At 2104 on 2 July an explosion generated an ash plume that rose 7-9 km above the crater rim, and ejected incandescent lava as far as 2 km onto the flanks. News articles noted that the deposits caused forest fires on the upper flanks, and that the event prompted about 700 people to evacuate. An event at 0413 on 3 July generated an ash plume that rose around 2 km. The Alert Level remained at 3 (on a scale of 1-4) and the exclusion zone was stable at a 4-km radius.

Great Sitkin | Andreanof Islands (USA) : AVO reported that after the brief explosion at Great Sitkin on 10 June seismicity gradually declined to background levels. On 27 June AVO lowered the Volcano Alert Level to Normal and the Aviation colour Code to Green.

Ibu | Halmahera (Indonesia) : Based on satellite images and model data, the Darwin VAAC reported that on 27 June an ash plume from Ibu rose to 1.8 km (6,000 ft) a.s.l. and drifted W. 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.

Krakatau | Indonesia : PVMBG reported that white plumes were seen rising as high as 100 m above Anak Krakatau during infrequent periods of clear weather from 27 June to 3 July. Incandescence from the summit was observed at night during 1-2 July. The Alert Level remained at 2 (on a scale of 1-4); residents and visitors were warned not to approach the volcano within 1 km of the crater.

Sierra Negra | Isla Isabela (Ecuador) : Based on video and photos shared by Parque Nacional Galápagos staff, IG reported that the eruption at Sierra Negra that began at 1340 on 26 June originated from several fissures on the N flank and one within the caldera. The flank flows reached the sea between Elizabeth Bay and Punta Morena. A gas-and-ash plume rose about 10.5 km and drifted W. Seismic and acoustic data indicated a gradual decrease but continuing activity on 27 June. A small seismic event was recorded at 1552 on 1 July, followed by at least four hours of tremor. At 1600 national park staff observed lava flows on the NW flank.

Yasur | Vanuatu : The Vanuatu Meteorology and Geo-hazards Department reported some stronger explosions at Yasur during 27-28 June. Based on webcam images the Wellington VAAC reported that on 29 June intermittent, low-level ash plumes rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted NW. The Alert Level remained at 2 (on a scale of 0-4). VGO reminded residents and tourists that hazardous areas were near and around the volcanic crater, within a 395-m-radius permanent exclusion zone, and that volcanic ash and gas could reach areas impacted by trade winds.