IMO reported that the fissure eruption in the W part of the Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, continued during 14-20 April. Lava flowed from about eight vents and the flow field continued to expand; on 14 April a new hiking trail (“A”) had been covered. Volcanic gas emissions were at dangerous levels during 14-15 April so the eruption site was closed to the public. At about 1500 on 17 April a new vent was confirmed to have opened. It was small and close to another crater, possibly the one that had opened on 13 April. Lava was not flowing from the northernmost crater (the first that had opened outside Geldingadalur) during 18-20 April.

The eruption had been ongoing for 30 days by 17 April. Based on a report from University of Iceland’s Institute of Earth Sciences, the average lava-flow rate during the first 17 days of the eruption was 4.5-5 cubic meters per second but had increased to 7 cubic meters per second over the previous 13 days. During 12-18 April the flow rate was closer to 8 cubic meters per second, a slight increase over the recent average. By 19 April the area of the flow field was 0.9 square kilometers and the total volume was over 14 million cubic meters.

IMO warned visitors that new fissures could open without adequate visible warning, especially in an area by Litla-Hrút, just S of Keilir, ʻwhere seismicity was concentrated. They also warned of increased gas emissions hazards. The Aviation Color Code remained Orange due to the lack of ash and tephra emissions.

Source: Icelandic Meteorological Office (IMO)

KVERT reported that a thermal anomaly over Karymsky was visible in satellite images during 9-12 April; weather conditions obscured views during 13-16 April. An explosion at 1745 on 11 April produced ash plumes that rose to 4 km (13,100 ft) a.s.l. and drifted 112 km SSE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

OVPF reported that the eruption at Piton de la Fournaise continued during 14-20 April. Lava fountaining was visible from both cones on most days, though sometimes inclement weather prevented visual observations of the eruption site. During an overflight on 16 April scientists observed that the most distal part of the lava flows had stopped advancing. The larger and more northern cone was 28 m high. The cone at a lower elevation, about 100 m away, had two vents. The smaller cone fed lava flows that traveled though tubes and emerged after 100 m, continuing to advance as many surficial breakout flows. The total length of the flow field was about 3.5 km and the maximum width was 750 m.

Sulfur dioxide emissions gradually increased between 400 and 859 tonnes per day during 9-12 April, peaked at 4,054 tonnes per day on 13 April, and then dropped to 2,100 tonnes per day on 14 April. OVPF estimated lava-flow rates based on the gas-emission rates, noting that weather conditions could affect the accuracy of the measurements. They estimated that the average flow rate in cubic meters per second was 20 during 9-10 April, an average of 24 with a maximum value of 59 on 13 April, 12.5 on 14 April, and 6.5-8.3 during 16-19 April. The Alert Level was raised to 2-2.

Source: Observatoire Volcanologique du Piton de la Fournaise (OVPF)

AVO reported that an eruption at Semisopochnoi continued during 14-20 April. Sulfur dioxide emissions were identified in satellite images during 13-14 April. An explosion was recorded by the regional infrasound network at 0417 on 14 April, though weather cloud cover as high as 4 km (13,000 ft) a.s.l. prevented satellite confirmation of an ash plume. Ash emissions began during the morning of 15 April and continued through the day, drifting more than 350 km SE at altitudes as high as 6 km (20,000 ft) a.s.l. They did not decrease in intensity, so at 1915 AVO raised the Aviation Color Code to Red and the Volcano Alert Level to Warning. Sustained ash emissions continued on 16 April, though the plume rose as high as 3 km (10,000 ft) a.s.l. and winds pushed it N. Explosions were detected through the night and early in the morning. Minor ash deposits around the volcano were visible. Eruptive activity declined during 16-17 April; one clear satellite view suggested that activity had declined or ceased. At 1249 on 17 April AVO lowered the Aviation Color Code to Orange and the Volcano Alert Level to Watch. Several explosions were recorded during 17-19 April though weather clouds obscured views. Volcanic plumes were visible just above the weather cloud deck (situated at 3 km (10,000 ft) a.s.l.) and drifted S during 19-20 April. A few darker (possibly ash rich) plumes were visible in satellite data at 0700 and 1150 on 19 April and on 20 April.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

University of the West Indies Seismic Research Centre (UWI-SRC) and National Emergency Management Organisation (NEMO) reported that the explosive eruption at Soufrière St. Vincent (often simply referred to as “La Soufriere”) continued during 14-20 April, though at a decreasing frequency. Explosions and pyroclastic flows were reported on 13 April, as well as lahars in the Sandy Bay area. During 14 April seismicity continued to be characterized by episodes of tremor, about 13-15 hours apart, separated by swarms of small, long-period (LP) earthquakes. An episode of tremor that began at 1135 was associated with increased explosive activity, though the emissions were gas rich and less energetic than previous events. Another episode of tremor began at 0230 on 15 April along with increased venting. Almost constant swarms of long-period and hybrid events were recorded through the day, punctuated by three brief episodes (less than 30 minutes) of low-level tremor. An episode of tremor began at 2100 and lasted 40 minutes, and was possibly associated with a minor increase in venting. For the first time sulfur dioxide emissions were successfully measured by ground-based instruments; scientists recorded 809 tons per day from a Coast Guard boat along the W coast.

Periods of tremor and near-constant swarms of LP and hybrid events were recorded on 16 April. An explosion at 0615 on 16 April generated an ash plume that rose about 8 km (26,200 ft) a.s.l. and drifted W. A three-minute period of high-level tremor started at the same time and was flowed by over two hours of lower-level tremor. Sulfur dioxide emissions were again measured from the W coast, yielding a flux of 460 tons per day. The rate of LP and hybrid events dropped significantly at 2000. Sulfur dioxide plumes reached India.

Occasional satellite images of the summit showed a series of changes to the new crater, centered in the SW part of the summit crater. By 17 April an Institut de Physique du Globe de Paris scientist reported that the crater was about 900 m N to S, at least 750 m E to W, and about 100 m deep based on RADAR data. Several vents were either visible or inferred from points of emissions. Sulfur dioxide emissions were 232 and 391 tons per day on 17 and 18 April, respectively. A period of high tremor began at 1649 on 18 April. An explosion produced an ash plume that rose to 8 km (26,200 ft) a.s.l. and drifted S and SW. This explosion occurred 52 hours after the last one and was the 30th since the explosive phase started. The period of tremor lasted until about 2100 and was followed by ongoing small LP and hybrid events. The rates of those events dropped again, at around 0100 on 19 April. One rockfall was detected by the seismic network at 0139, and two were noted the next day. At 0400 on 20 April a lahar was detected by the seismic network and lasted for 30 minutes; it possibly traveled down the SE flank.

During 15-19 April NEMO reported details about the people that have evacuated. The total number of displaced people was 12,775 by 19 April, with 6,208 people in 85 public shelters and 6,567 people (1,800 families) in private shelters. There were no casualties caused by the eruption.

Sources: University of the West Indies Seismic Research Centre (UWI-SRC), National Emergency Management Organisation (NEMO), Government of Saint Vincent and the Grenadines, Advanced geospatial Data Management Platform (ADAM)

JMA reported that during 12-19 April incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible nightly. There was a total of nine explosions and one eruptive event. Ash plumes rose 1-2 km above the summit and bombs were ejected 800-1,300 m away from the crater. The sulfur dioxide emission rate was high at 2,400 tons per day on 12 April. The Alert Level remained at 3 (on a 5-level scale).

Source: Japan Meteorological Agency (JMA)

Based on satellite and wind model data, the Darwin VAAC reported that during 13-20 April ash plumes from Dukono rose to 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted E and NE. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

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

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 9-16 April that sent ash plumes to 3.6 km (11,800 ft) a.s.l. and drifted in multiple directions. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

Based on satellite and wind model data, the Darwin VAAC reported that on 15 April ash plumes from Kadovar rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted W.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)

HVO reported that the W vent on the inner NW wall of Kīlauea's Halemaʻumaʻu Crater continued to supply the lava lake during 14-20 April. Lava flowed at a low rate from the main vent into the lake through crusted-over channels and submerged inlets. The depth of the lake was about 226-227 m and lava continued to circulate in the W part, though the active area continued to shrink; the E half of the lake remained solidified. Lava sometimes overflowed the margins of the lake. The sulfur dioxide emission rate was 950 tons/day on 14 April. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

PVMBG reported that the eruption at Lewotolok continued during 13-19 April. Gray-and-white ash plumes rose as high as 1.5 km above the summit and drifted E and W. Rumbling was often audible. Incandescent material was ejected 300-1,000 m above the summit during 14-16 April. Incandescent material was ejected to the E during 9 and 11-12 April. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 4 km away from the summit crater.

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

BPPTKG reported that the lava dome just below Merapi’s SW rim and the lava dome in the summit crater both continued to extrude lava during 9-15 April. The SW rim lava-dome volume was an estimated 1,024,800 cubic meters on 15 April, with a growth rate of about 12,200 cubic meters per day, and continued to shed material down the flank. A total of six pyroclastic flows traveled a maximum of 1.8 km down the SW flank. Incandescent avalanches, recorded 119 times, traveled as far as 1.5 km down the SW flank. The volume of the summit lava dome was 1,681,000 cubic meters on 14 April. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 5 km away from the summit.

Source: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG)

CENAPRED reported that each day during 13-20 April there were 14-34 steam, gas, and ash emissions from Popocatépetl and periods of tremor lasting from 5-15 hours. Two volcanic earthquakes were recorded at 1054 and 2354 on 16 April. Minor crater incandescence was visible overnight during 17-18 April. A M 1.3 volcano-tectonic earthquake was recorded at 2057 on 18 April. The Alert Level remained at Yellow, Phase Two (middle level on a three-color scale).

Source: Centro Nacional de Prevencion de Desastres (CENAPRED)

PVMBG reported that gray-and-white ash plumes rose 50-400 m above Raung's summit during 13-14 April and drifted N, NE, E, and S. Emissions were white and rose as high as 400 m during 15-16 and 19 April. Weather conditions prented visual observations on some days. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

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

Instituto Geofísico del Perú (IGP) reported a daily average of 91 explosions at Sabancaya during 12-18 April. Gas-and-ash plumes rose as high as 2.3 km above the summit and drifted S, SW, NW, and N. Eight thermal anomalies originating from the lava dome in the summit crater were identified in satellite data. Minor inflation continued to be detected near Hualca Hualca (4 km N). The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12-km radius.

Source: Instituto Geofísico del Perú (IGP)

IG reported a high level of activity at Sangay during 13-20 April. Seismicity was characterized by daily explosions, long-period earthquakes, lahar events, and signals indicating emissions. Weather clouds and rain often prevented visual observations of the volcano, though based on the Washington VAAC and webcam images, ash plumes were visible during 13-14 and 17-20 April rising 600-2,400 m above the summit and drifting mainly N, NW, and W. The seismic network occasionally recorded lahar signals, especially during 14-16 April. Ashfall was reported in Chimborazo (W) and Guamote (40 km WNW) on 17 April, and crater incandescence was visible through the night of 19-20 April.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)

PVMBG reported that at 0650 on 19 April an ash plume from Semeru rose 400 m above the summit and drifted W. The Alert Level remained at 2 (on a scale of 1-4), with a general exclusion zone of 1 km and extensions to 5 km in the SSE sector.

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

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 9-16 April. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

PVMBG reported that on 13 April eruptive events at Sinabung generated ash plumes that rose 500-1,600 m above the summit. Avalanches of material traveled 1-1.5 km. On 14 April gray ash plumes rose 500 m above the summit and avalanches traveled 500-700 m down the E and SE flanks. During 15-20 April white plumes were often seen rising as high as 700 m, though weather conditions sometimes prevented visual observations. The Alert Level remained at 3 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions to 5 km in the SE sector and 4 km in the NE sector.

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

JMA reported that incandescence from Suwanosejima's Ontake Crater was visible at night during 9-16 April. Seven explosions generated ash plumes that rose as high as 1.5 km above the crater rim and ejected bombs 400 m away. Ashfall was reported in Toshima village (4 km SSW). The Alert Level remained at 2 and the public was warned to stay 1 km away from the crater.

Source: Japan Meteorological Agency (JMA)

AVO reported that communication was reestablished with two seismic stations on Tanaga, making a total of four operational stations. On 19 April AVO changed both the Aviation Color Code and the Volcano Alert Level to Green and Normal, respectively, reflecting the resumption of seismically monitoring unrest.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

AVO reported a loss of operation and communication with seismic stations that monitor Ugashik-Peulik, likely caused by snow cover. Both the Aviation Color Code and the Volcano Alert Level were changed to Unassigned on 19 April, reflecting the inability to locate earthquakes to detect unrest. Monitoring will continue with the remaining seismic stations, regional infrasound networks, lightning detection, and satellite images.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

AVO reported a loss of operation and communication with seismic stations that monitor Ukinrek-Maars, likely caused by snow cover. Both the Aviation Color Code and the Volcano Alert Level were changed to Unassigned on 19 April, reflecting the inability to locate earthquakes to detect unrest. Monitoring will continue with the remaining seismic stations, regional infrasound networks, lightning detection, and satellite images.

Source: US Geological Survey Alaska Volcano Observatory (AVO)