Report for Etna
INGV reported that gas emissions of variable intensity were observed rising from Etna’s summit craters during 14 and 17-19 May; weather conditions prevented views on the other days during 13-19 May. Ash emissions periodically rose from vents in the S and E parts of New Southeast Crater (NSEC). Several Strombolian explosions at NSEC ejected incandescent pyroclastic material a few dozen meters above the crater rim during 17-18 May.
Report for Sinabung
PVMBG reported that white plumes rose as high as 700 m above Sinabung’s crater rim during 13-21 May. On 20 May the Alert Level was lowered to 3 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions to 5 km on the SE sector and 4 km in the NE sector. PVMBG noted that the seismic activity surrounding the recent ash emissions during 7 and 11-12 May were not indicative of renewed activity.
Report for Krakatau
PVMBG reported that Anak Krakatau’s seismic network detected 22 eruptive events during 13-19 May, though none of the events were followed by ash emissions. Dense white plumes were visible rising as high as 200 m above the summit during periods of clear weather. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km radius hazard zone around the crater.
Report for Merapi
PVMBG reported that on 11 May the lava dome at Merapi had an estimated volume of 458,000 cubic meters, based on analyses of drone footage. The dome morphology remained relatively unchanged during 12-19 May, as most of the extruded lava fell into the upper parts of the SE-flank Gendol River drainage. Two block-and-ash flows traveled as far as 1.2 km down the Gendol drainage. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to remain outside of the 3-km exclusion zone.
Report for Agung
PVMBG reported that at 1409 on 18 May an explosion at Agung ejected incandescent material radially onto the flanks as far as 2.5 km from the crater rim. A dense gray-white ash plume rose 2 km and drifted NE, E, and SE, causing ashfall in hamlets downwind including Cutcut, Tongtongan, Bonyoh, and Temakung. A weak roar was audible from the Agung Volcano Observatory in Rendang (about 8 km SW). The Alert Level remained at 3 (on a scale of 1-4) with the exclusion zone set at a 4-km radius.
Report for Dukono
Based on satellite and wind model data, and notices from PVMBG, the Darwin VAAC reported that during 15-21 May ash plumes from Dukono rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted in multiple directions. 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.
Report for Ibu
The Darwin VAAC reported that during 14-16 and 18-19 May ash plumes from Ibu rose to 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted NW, N, ENE, and SE based on satellite data. 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.
Report for Aira
JMA reported that on 13 May two explosions at Minamidake crater (at Aira Caldera’s Sakurajima volcano) produced plumes that rose 1.8 km above the crater rim and ejected material as far as 1.3 km. Crater incandescence from the crater was visible. Very small non-explosive events were recorded by the seismic network during 17-20 May. The Alert Level remained at 3 (on a 5-level scale).
Report for Asosan
JMA reported that during 15-20 May sulfur dioxide emission levels were somewhat high at Asosan’s Nakadake Crater. At 1028 on 15 May an eruption produced a plume that rose 700 m above the crater rim. White plumes rose 200 m during 17-20 May. The Alert Level remained at 2 (on a scale of 1-5).
Report for Hakoneyama
JMA reported that the number of earthquakes at Hakoneyama increased during 18-19 May, with epicenters centered around the W bank of Lake Ashinoko and around Komagatake. Fumaroles in the Owakudani hot springs area continued to be active. Global Navigation Satellite Systems (GNSS) data showed changes in deformation beginning in mid-March. On 19 May JMA raised the Alert Level to 2 (on a 5-level scale). Elevated seismicity continued to be recorded through 21 May.
Report for Azumayama
The number of volcanic earthquakes at Azumayama increased on 5 May and data from a tiltmeter about 1 km SE of Ohana Crater showed inflation on 9 May, prompting JMA to raise the Alert Level to 2 (on a 5-level scale). Field observations on 7 and 10 May indicated no changes in the fumarolic and thermal areas around Ohana. Seismicity began to decrease on 10 May, though continued to fluctuate through 20 May. Deformation continued but at a slower rate.
Report for Sarychev Peak
SVERT reported that a weak thermal anomaly over Sarychev Peak was visible in satellite images on 10, 12, and 17 May. At 0830 on 16 May satellite images showed an ash plume drifting 50 km SE at an altitude as high as 2.5 km (8,200 ft) a.s.l. The Aviation Color Code was raised to Yellow on 16 May.
Report for Ebeko
A thermal anomaly over Ebeko was identified in satellite images during 12-13 May. Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 13-15 May that sent ash plumes up to 2.5 km (8,200 ft) a.s.l. Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Report for Karymsky
KVERT reported that a thermal anomaly over Karymsky was visible in satellite images during 10-14 May. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Report for Klyuchevskoy
KVERT reported that a weak thermal anomaly over Klyuchevskoy was identified in satellite images on 10 and 15 May. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Report for Sheveluch
KVERT reported that a thermal anomaly over Sheveluch’s lava dome was identified daily in satellite images during 10-17 May. Plumes of re-suspended ash were visible drifting 16 km SE on 13 May. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Report for Pavlof
AVO reported that low-frequency tremor was detected at Pavlof during 14-15 May and a vigorous steam plume rising from the summit was visible in webcam images on 15 May. The Aviation Color Code was raised to Yellow and the Volcano Alert Level was raised to Advisory primarily because of increased seismicity. Steam plumes recorded by the webcam, low levels of seismic tremor, and warm surface temperatures identified in satellite data continued during 16-19 May; AVO noted that steam emissions and warm surface temperatures are common at Pavlof.
Report for Popocatepetl
CENAPRED reported that each day during 15-21 May there were 22-72 steam-and-gas emissions from Popocatépetl, some of which contained ash (19-21 May). Two explosions, at 0817 and 0831 on 16 May, generated ash plumes that rose 1.6 and 1 km above the crater rim, respectively. During 20-21 May crater incandescence was visible during some emissions. The Alert Level had returned to Yellow, Phase Two (middle level on a three-color scale) on 7 May and remained there through 21 May.
Report for Santa Maria
INSIVUMEH reported that during 16-17 May there were two explosions per hour detected at Santa María's Santiaguito lava-dome complex. Ash plumes rose 700 m above the complex and drifted SW. Eight weak explosions were recorded during 19-20 May, generating ash plumes that rose 700 m and drifted SW. Avalanches of material descended the E and SE flanks of the lava dome.
Report for Fuego
INSIVUMEH reported that there were 15-20 explosions per hour recorded at Fuego during 16-17 and 19-20 May, generating ash plumes that rose as high as 1.1 km above the crater rim and drifted 10-25 km S, SW, and W. Explosions sometimes produced shock waves that rattled houses in nearby communities. Incandescent material was ejected 300-400 m high and caused avalanches of material that occasionally traveled long distances (reaching vegetated areas) down Seca (W), Taniluyá (SW), Ceniza (SSW), Trinidad (S), and Las Lajas (SE) ravines. Ashfall was reported in areas downwind including Santa Sofía (12 km SW), Morelia (9 km SW), Panimaché I and II (8 km SW), and El Porvenir (8 km ENE). A lava flow on the W flank was 300 m long.
On 16 May lahars carrying variously-sized blocks and tree branches and trunks descended the Las Lajas ravine. On 20 May hot lahars with a sulfur odor descended the Ceniza, El Jute, and Las Lajas drainages, carrying blocks 1-3 m in diameter.
Report for Rincon de la Vieja
OVSICORI-UNA reported that phreatic eruptions at Rincón de la Vieja were recorded at 1703 on 14 May and 0357 on 17 May, though dense fog prevented visual confirmation of both events with webcams. On 15 May a local observer noted a diffuse plume of steam, gas, and particulates rising from the crater and photographed milky-gray deposits on the N part of the crater rim, ejected from the event the day before.
Report for Turrialba
On 19 May OVSICORI-UNA reported that passive, short-duration emissions with small amounts of ash had been sporadically occurring at Turrialba over the previous week. Prolonged and intermittent periods of emissions with minor amounts of ash were visible during 19-20 May.
Report for Reventador
IG reported that during 14-21 May seismic data from Reventador’s network indicated a high level of seismic activity, including explosions, long-period earthquakes, harmonic tremor, and signals indicating emissions. Weather conditions often prevented views of the summit area, although when clear (during 17-18 and 20-21 May) several ash plumes were visible rising as high as 1 km above the crater rim and drifting W and NW. Crater incandescence was visible on some mornings and evenings. On 19 May a 500-m-long pyroclastic flow deposit on the N flank was visible. Blocks were observed rolling 800 m down the flanks on 21 May.
Report for Sangay
IG reported that a new eruption at Sangay began on 7 May and was continuing as of 21 May. Activity was concentrated at two eruptive centers; the Central Crater and the Ñuñurcu dome (located 190 m SSE of Central Crater). Explosive activity at Central Crater produced ash plumes that rose an average of 1 km above the crater rim and drifted W and NW. Ejected blocks rolled as far as 2.5 km down the SE flank. The Ñuñurcu dome produced a lava flow that had a maximum width of 175 m and traveled about 470 m down the SE flank. Collapses of the lava-flow front generated small pyroclastic flows and numerous block flows; one of the pyroclastic flows traveled 340 m.
Report for Sabancaya
Instituto Geofísico del Perú (IGP) and Instituto Geológico Minero y Metalúrgico (INGEMMET) reported that an average of 33 low-to-medium intensity explosions per day occurred at Sabancaya during 13-19 May. Gas-and-ash plumes rose as high as 2.5 km above the crater rim and drifted NW, N, and NE. There were 10 thermal anomalies identified in satellite data. The report noted that the public should not approach the crater within a 12-km radius.
Report for Villarrica
POVI reported continuing activity at Villarrica during 5-6 May when Strombolian explosions ejected lava 50 m above the crater rim. On 14 May the webcam recorded 24-m-wide lava fountains rising as high as 70 m. An explosion later that day at 2220 ejected a mushroom-shaped fountain 70 m high. POVI noted it was one of the largest lava explosions since 2015.