Roundup of Global Volcanic Activity – New Activity for the week of 25 July – 31 July 2018
Ambae | Vanuatu : Vanuatu Meteorology and Geo-hazards Department (VMGD) reported that during overflights on 13 and 20 July, observers took photos of explosions at Ambae’s Lake Voui ejecting hot tephra from vents and producing ash plumes. Increased activity prompted VMGD to raise the Alert Level to 3 (on a scale of 0-5) on 21 July, and warn residents to stay at least 3 km away from the active crater. The report noted that current activity was similar to that in March, but with more sustained ash emissions. At about 2100 on 26 July explosions generated an ash cloud that rose as high as 12 km above the vent and spread NE, E, and SE. According to news articles, the event caused darkness in the daytime and prompted an order for an island-wide evacuation of the 10,000 residents. Another explosive event occurred early on 27 July. The Wellington VAAC reported sulfur dioxide emissions, and ash plumes rising to 2.4-4.6 km (8,000-15,000 ft) a.s.l. and drifting SE and NW. Pilots reported heavy ashfall over eastern Fiji. Smaller events producing ash-and-gas emissions continued throughout the day. On 1 August VMGD stated that the ashfall has had a significant impact on the island’s food and water supplies, and the health of the island residents.
Ibu | Halmahera (Indonesia) : PVMBG reported that at 1852 on 28 July an event at Ibu generated an ash plume that rose 5.5 km above the crater rim and drifted SE. An event at 1612 on 29 July produced an ash plume that rose 4.8 km and drifted N. Ash plumes later drifted SE. Seismic signals for both events were characterized by explosions and avalanches. 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 : Based on satellite and wind model data, the Darwin VAAC reported that during 25-26 July minor ash plumes from Anak Krakatau rose to an altitude of 1.2 km (4,000 ft) a.s.l. and drifted SW and NW. PVMBG noted that inclement weather conditions prevented views of the volcano during 27-30 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.
Rincon de la Vieja | Costa Rica : OVSICORI-UNA reported that a small explosion at Rincón de la Vieja was recorded at 1828 on 28 July, and was followed by tremor.
Semeru | Eastern Java (Indonesia) : Based on analysis of satellite images, the Darwin VAAC reported that on 31 July an ash plume from Semeru rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted W.
Sierra Negra | Isla Isabela (Ecuador) : IG reported that the eruption at Sierra Negra continued during 25-31 July. Sulfur dioxide flux was as high as about 1,400 tons per day (on 28 July), and daily counts of volcano-tectonic and long-period events were 24-65 and 3-32, respectively. Nightly incandescence from advancing lava flows was visible. Gas plumes rose more than 1.8 km above the vents and drifted N, NW, and W.
Villarrica | Chile : POVI reported that on 24 July the vent in Villarrica’s summit crater was about 10-15 m in diameter and 90-100 m below the crater rim. Minor explosions and weak fumarolic emissions were noted. On 29 July a break in the cloud cover revealed more significant incandescence emanating from the summit than in the previous few days, and the largest thermal anomaly since August 2015 was identified in satellite images on 30 July. Ash and lapilli deposits on the E edge of the crater was also visible on 30 July.