Volcano World

A plume of discolored water surrounding Ahyi Seamount was identified in satellite data on 15 December, indicating continued low-level unrest. Signals from underwater activity coming from the direction of Ahyi were identified in data from underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi) on 24 and 26 December (UTC). Satellite data from those days were obscured by clouds; no evidence of discolored water was identified in a partly cloudy satellite image from 25 December. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Source: US Geological Survey

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that a phreatic eruption occurred from the E part of Sileri Crater in the Dieng Volcanic Complex on 18 December and was not preceded by significant signs of elevated volcanic activity. The eruption began at 1512 and lasted for three minutes and 20 seconds based on seismic data. Sediment and mud were ejected about 100 m N and E, about 25 m W, and about 10 m S. An eruption plume was partially hidden due to inclement weather conditions, but observers reported seeing a white plume rise 10 m. After the eruption white plumes rose as high as 40 m above the crater. The water temperature of the lake did not increase. The water color varied in different locations appearing clear, greenish, or light-to-blackish gray, and the volume was lower. Sediment and mud deposits ringed the crater and there was a notable sulfur odor. Primary hazards at Dieng included phreatic eruptions at Sileri, Siglagah, Pagerkandang, and Candradimuka craters, along with the emission of volcanic gases at several more craters that could affect people nearby. Based on the data and potential hazards at the complex, PVMBG raised the Alert Level to 2 (on a scale of 1-4) at 1800 on 19 December. The public was warned to stay 500 m away from Sileri Crater and not to spend the night around the crater, to stay out of Timbang Crater and other potentially hazardous craters, and to take caution when digging in the ground as gasses could be released. PVMBG conducted an inspection of the crater on 22 December and noted that monitoring parameters (visual, temperature, gas, and seismicity) were at normal levels. The team also visited other craters including Sikendang-Telagawarna Crater, Sikidang Crater, and Candradimuka Crater. There was no increased activity at the craters, though some gas concentrations remained at relatively high levels near or around the gas vents.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 17-31 December. The seismic network recorded 8-26 daily volcanic earthquakes during 17-22 December, along with sulfur dioxide emissions ranging from 4,208 to 7,445 tonnes per day. Weather clouds mostly prevented views of the summit but on 18 December emissions were seen rising 100 m above the summit and drifting SW. At 1145 on 23 December dark ash emissions began rising from the crater and were accompanied by low-frequency volcanic tremor. The plumes rose 1.2 km above the crater, drifted NW, and were continuous at least through 1230, when a special report was issued. Almost daily ash emissions occurred during 24-30 December; 2-9 periods of ash emissions each day except for 27 December ranged from three minutes to two hours and 26 minutes. The emissions rose as high as 1.2 km above the crater rim and drifted NW, W, SW, and SSW and were voluminous during 28-30 December. Seismicity was characterized by 16-25 daily volcanic earthquakes and 2-11 daily periods of tremor lasting as short as three minutes to as long as one hour and 32 minutes. sulfur dioxide emissions continued to be elevated, ranging from 2,200 to 7,705 tonnes per day. The eruption continued to impact residents. The National Disaster Risk Reduction and Management Council (NDRRMC) report issued at 0800 on 31 December stated that 14,441 people (4,420 families) were spread across 34 evacuation centers and another 6,977 people (2,192 families) were staying elsewhere. The report also stated that 34 cities were under a ?state of calamity?, jobs continued to be affected, and some classes remained suspended. The Alert Level remained at 3 (on a scale of 0-5); the public was warned to stay 6 km away from the summit and pilots were warned not to fly close to the volcano.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS) ,The National Disaster Risk Reduction and Management Council (NDRRMC)

The Hawaiian Volcano Observatory (HVO) reported that the eruption that began at 0220 on 23 December continued during 24-30 December from vents located at the SW margin of Halema?uma?u Crater within Kilauea?s Kaluapele summit caldera. Fissures opened at 0220 on 23 December producing lava fountains and lava flows that advanced across the Halema?uma?u Crater floor and overflowed onto the down-dropped block area to the E. The eruption had paused by 1600 on the 23rd, but at 0800 on 24 December several of the vents began erupting slow-moving lava flows. Lava fountaining was visible and intensified at 1100. Breakouts of lava were visible on the surface of the lava lake on the crater floor as it continued to circulate. Vigorous lava fountains rose 75 m high from a main vent during 1430-1615. A significant amount of tephra from the fountaining during 23-25 December accumulated on the closed portion of Crater Rim Drive, producing deep drifts of cinder over and alongside the road. Lava flows continued to spread across the crater floor on 25 December, covering lava from the first day of the eruption, or just under 2.6 square kilometers. Lava flows on the crater floor were a few meters deep. Minutes before 1100 on 25 December the lava fountains decreased, and at 1100 lava drained back into the vent. At around the same time summit tiltmeters began recording a change from deflation to inflation and seismic tremor decreased. Sulfur dioxide emissions remain elevated, with a gas plume rising above the caldera, but the vigor of the outgassing notably decreased. Lava flows on the crater floor stagnated. Minor lava effusion began again around 0800 on 26 December from the SW vents. Scientists in the field reported numerous rockfalls from the crater walls. Small lava flows traveled short distances from the vent during 26-27 December, causing an elevated ?pad? of lava about 140 x 170 m in size and elevated about 2-3 m above the darker surrounding lava lake. The vents produced spatter and low-level fountaining. More vigorous fountaining began at around 1800 on 27 December with periodic fountain bursts rising 10-15 m above the vents. Sulfur dioxide emissions were elevated, with a gas plume rising above the caldera, but outgassing vigor was greatly reduced compared to the periods of higher lava fountaining in previous days. Deflation began in the S part of the caldera at around 1300 and tiltmeter data showed the inflation had flattened beneath Halema?uma?u Crater by 1500. Fountaining from the more south of two active vents increased and became more continuous at 1715 on 28 December. Lava was ejected 20-30 m high. By 1800 the advancing lava flows had covered about 20 percent of the crater floor. Tremor levels had been gradually increasing over the past two days but were relatively low compared to earlier periods of vigorous fountaining. Sustained lava fountaining 30-40 m high continued during 29-31 December. A large fan of lava covered the SW part of the crater floor and advanced towards the central part of the floor. Sulfur dioxide emissions drifted SW.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

According to news articles a minor explosion at Masaya around 1500 on 22 December produced a gas-and-ash plume that rose above the crater. Though the activity was characterized as normal the Masaya Volcano National Park was temporarily closed as a safety precaution. Fumarolic activity and nighttime incandescence in the crater had been ongoing.

Source: TN8 Nicaragua

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported an eruption at Raung on 24 December. The eruption occurred at 0930 and lasted about four minutes and 42 seconds. A dense gray ash plume rose around 2 km above the summit and drifted E. The seismic network detected subsequent eruptive events at 1025, 1031, and 1035, though foggy weather prevented visual observations. According to the Darwin VAAC an ash plume from an eruption already in progress was identified in a satellite image at 1000 rising to 6.1 km (20,000 ft) a.s.l., or 2.8 km above the summit, and drifting NE. A second, discrete eruption plume was identified in a satellite image at 1050 rising to 7.9 km (26,000 ft) a.s.l., or 4.6 km above the summit, and drifting NW. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 3 km away from the summit crater.

Sources: Darwin Volcanic Ash Advisory Centre (VAAC),Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)

The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Caldera?s Sakurajima volcano) during 16-30 December; activity intensified on 23 December and remained elevated. Nightly crater incandescence was visible in webcam images. Occasional small eruptive events were recorded during 16-19 December. On 17 December sulfur dioxide emissions were averaging 3,400 tons per day. Eruptive events at 1340, 1847, 1939, and 2112 on 20 December produced ash plumes that rose 1-1.3 km above the crater rim and drifted N and NE. Explosions at 0059 on 21 December and 0029 on 22 December produced ash plumes that rose 700-900 m above the crater rim and drifted N and SE. The explosions ejected large blocks 300-500 m from the crater rim. An explosion at 0710 on 23 December generated an ash plume that rose 1.6 km above the crater rim and drifted SE and ejected large blocks 300-500 m from the crater rim. An explosion almost 20 minutes later, at 0729, produced an ash plume that rose 3.4 km above the crater rim and drifted SE. Large blocks were ejected 600-1,000 m from the crater. Plumes had not risen more than 3 km since an explosion produced a 4-km-high plume on 18 October. On 24 December sulfur dioxide emissions were averaging 2,000 tons per day. Another ash plume from an eruptive event at 1641 on 27 December rose 2.2 km above the crater rim and drifted SE. At 1719 an explosion generated an ash plume that rose 900 m and drifted SE, and ejected large blocks 500-800 m from the crater rim. An explosion at 0812 on 29 December generated an ash plume that rose 500 m and drifted SE, and ejected blocks 500-700 m from the rim. A few hours later an ash plume from an explosion at 1128 rose 1.5 km above the crater rim and drifted SE, followed by an eruptive event at 1506 that sent an ash plume to 1.2 km above the crater rim and drifted SE. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 1 km away from both craters.

Source: Japan Meteorological Agency (JMA)

On 31 December the Vanuatu Meteorology and Geohazards Department (VMGD) reported that steam-and-gas emissions from the active vents at Ambae were ongoing during December based on satellite images. A low-level thermal anomaly was identified in satellite data on 21 December indicating an increase in surface temperatures. Seismic data also confirmed ongoing unrest. The Alert Level remained at 2 (on a scale of 0-5), and the public was warned to stay outside of the Danger Zone, defined as a 2-km radius around the active vents in Lake Voui, and away from drainages during heavy rains.

Source: Vanuatu Meteorology and Geohazards Department (VMGD)

On 31 December the Vanuatu Meteorology and Geohazards Department (VMGD) reported ongoing fumarolic activity at Ambrym from both Benbow and Marum craters based on webcam images. Thermal anomalies were identified in satellite images on 4, 18, and 27 December, indicating increased surface temperatures. Sulfur dioxide emissions were detected on 27 December. Seismic data confirmed ongoing unrest. The Alert Level remained at 2 (on a scale of 0-5). VMGD warned the public to stay outside of Permanent Danger Zone A, defined as a 1-km radius around Benbow Crater and a 2-km radius around Marum Crater, and to stay 500 m away from the ground cracks created by the December 2018 eruption.

Source: Vanuatu Meteorology and Geohazards Department (VMGD)

The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Dukono was ongoing during 18-31 December. No plumes were visible during 18-19 December and white gas-and-steam plumes rose 100-600 m above the crater rim and drifted E and SE during 20, 24-25, and 28 December. White-and-gray ash plumes rose 100-700 m above the crater rim and drifted E, SE, and S during 21-23, 26-27, and 29-31 December. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)