Volcanos

Roundup of Global Volcanic Activity – New Activity for the week of 4 April - 10 April 2018

Ambae | Vanuatu : Vanuatu Geohazards Observatory (VGO) reported sustained ash and/or gas emissions from Ambae’s Lake Voui during March through 4 April. Satellite data showed a significant sulfur dioxide gas emission (~0.15 Tg SO2) beginning in the very early hours of 6 April, indicating that the SO2 emission was the largest since Calbuco in April 2015. No significant high-altitude ash plume accompanied the emission, though the eruption generated lightning detected by the WWLLN (World Wide Lightning Location Network). Pictures of local areas posted on social media showed the continuing and significant ashfall on the island. Within a few days, by 8 April, the sulfur dioxide plume had spread across an area from the E coast of Australia to Tahiti, a distance of about 6,000 km. The Alert Level remained at 3 (on a scale of 0-5).

Kirishimayama | Kyushu (Japan) : JMA reported that an explosive eruption at Shinmoedake (Shinmoe peak), a stratovolcano of the Kirishimayama volcano group, occurred at 0531 on 5 April and generated an ash plume that rose 8 km above the crater rim. According to news articles lightning was detected in the ash plume. JMA noted that incandescent tephra was ejected 1.1 km from the vent, and a pyroclastic flow traveled 800 m down the SE flank. Sulfur dioxide emissions increased to 1,400 tons/day, from 300 tons/day last measured on 28 March. The eruption possibly ceased at 0715. During an overflight later that day scientists confirmed a large amount of ashfall in parts of Kobayashi City and other areas of the Miyazaki Prefecture, in part of Takahara Town, and in areas of the Kumamoto prefecture. White plumes rose 200 m during 6-9 April. The Alert Level remained at 3 (on a scale of 1-5).

Lascar | Chile : OVDAS-SERNAGEOMIN reported that, although seismicity at Láscar during March was low, characteristics of the signals were similar to patterns observed prior to previous minor phreatic explosions, particularly before events in 2013 and 2015. The Alert Level was raised to Yellow (second highest level on a four-color scale); SERNAGEOMIN recommended no entry into a restricted area within 5 km of the crater. ONEMI declared an Alert Level Yellow (the middle level on a three-color scale) for San Pedro de Atacama.

Nevados de Chillan | Chile : Servicio Nacional de Geología and Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur (OVDAS) reported continuing activity through 5 April associated with growth of the Gil-Cruz lava dome in Nevados de Chillán’s Nicanor Crater. During 16-31 March the seismic network recorded 44 volcano-tectonic events with maximum local magnitude (ML) of 2.6. In addition, there were 3,874 earthquakes associated with fluid movement; of those 2,645 earthquakes were long-period events. A total of 1,229 tremor events were also detected. Explosive events totaled 765, mainly accompanying magmatic gas emissions and/or acoustic signals recorded by microphones on the flanks. Acoustic pressure from explosions increased on 24 March, and culminated with two major explosions on 30 and 31 March exceeding pressures much higher than previously recorded since the emergence of the dome. Webcam images showed mainly gas emission from explosions, rising no higher than 2 km above the crater rim. Incandescence associated with some explosions was sporadically visible at night. During an overflight on 3 April scientists observed intermittent whitish-to-grayish emissions rising from the SE-NW-trending fissure on the lava dome’s surface. They also noted lapilli deposits as far as 1 km. Even though subsidence in the central part of the dome was visible, the dome had grown compared to the last observation on 11 March. The dome had extended E to the edge of Nicanor Crater and rose higher than the crater rim, although was mostly circular. The maximum temperature of the dome surface was 670 degrees Celsius. The report noted that a decrease in daily seismic events (suggesting pressurization), two significant explosions, and the dome growing higher than the crater rim prompted OVDAS- SERNAGEOMIN to raise the Alert Level to Orange, the second highest level on a four-color scale. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián.

Sinabung | Indonesia : PVMBG and BNPB reported that an eruption at Sinabung at 1607 on 6 April generated a dark gray ash plume that rose 5 km above the crater, and a pyroclastic flow that descended the SE and SW flanks 3.5 km. The Alert Level remained at 4 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions of 7 km on the SSE sector, 6 km in the ESE sector, and 4 km in the NNE sector. According to news articles, ashfall affected hundreds of hectares of agricultural land in the district of Karo, North Sumatra, and the Alas Leuser airport was closed on 7 April due to ash. The Alert Level remained at 4 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions of 7 km on the SSE sector, 6 km in the ESE sector, and 4 km in the NNE sector.