INGEMMET reported that on 18 April, explosions from Ubinas produced gas and ash plumes to altitudes of 5.9-7.7 km (19,400-25,300 ft) a.s.l. Plumes drifted SW. Based on significant meteorological (SIGMET) notices, satellite imagery, and pilot reports, the Buenos Aires VAAC reported that ash plumes rose to altitudes of 5.5-7 km (18,000-28,000 ft) a.s.l. on 17, 18, 22, and 24 April. Plumes drifted NW, SW, and SE.
IG reported that during 17-18 April, Strombolian activity from Tungurahua was observed; incandescent material was ejected about 500 m above the summit and blocks descended down the flanks. Lahars carring large blocks NW down the Mandur gorge caused a road closing on 19 April. During 17-24 April, ash plumes rose to altitudes of 5.5-9 km (18,000-29,500 ft) a.s.l. and drifted W and N. Ashfall was reported from areas mainly to the N, NW, W, and SW during 17, 19, 21-22, and 24 April. On 23 April, lahars were observed in several gorges to the NW. Clouds occasionally inhibited views of the summit during the reporting period.
Data from deformation-monitoring instruments and observations from a remote camera showed that during 18-24 April lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels, punctuated by M 1.5-2.5, and occasionally larger, earthquakes. In some instances, clouds inhibited visual observations.
During 13-20 April, visual observations suggested that lava-dome growth at Soufrière Hills continued at a reduced rate. Material originating from the lava dome’s growing E-facing shear lobe was shed down the Tar River Valley. Heavy rains resulted in lahars in several drainages 16-17 April. During 18-20 April, a gas plume drifted N and NE and a bluish haze containing sulfur dioxide was observed flowing down the N flanks due to light winds coming from the S.
Background levels during 13-20 April. Based on seismic interpretation, observation, and video data, ash-and-steam plumes possibly rose to altitudes of 5.5-6.5 km (18,000-21,300 ft) a.s.l. throughout the reporting period. Plumes were seen on satellite imagery drifting E, SE, and S and a thermal anomaly was present. Base on pilot reports, satellite imagery, KEMSD, and observations from the Petropavlovsk-Kamchatsky Flight Information Region (FIR), the Tokyo VAAC reported that ash plumes rose to altitudes of 4.6-6.1 km (15,000-20,000 ft) a.s.l. during 18-22 April. They drifted E. The Level of Concern Color Code remained at Orange
INSIVUMEH reported that explosions from Santa María's Santiaguito lava dome complex on 20 and 23 April occasionally produced ash plumes that rose to altitudes of 5.3 km (17,400 ft) a.s.l. The plumes drifted SW and ashfall was reported from areas up to 9 km to the SW. On 23 April, lava flows on the SW and NE flanks of Caliente dome produced small landslides composed of blocks.
On 18, 20, and 23 April, steam-and-gas emissions from Reventador hung near the summit. On 18 April, a plume was seen drifting NW on satellite imagery. On 20 April, a bluish haze of gases was observed. Clouds occasionally inhibited views of the summit during 18-24 April.
During 13-20 April, Strombolian activity occurred at Kliuchevskoi, based on observations and video data. Seismic activity continued above background levels and a thermal anomaly in the crater was detected on satellite imagery. Fumarolic activity intensified during 15 and 17-18 April. Gas-and-steam plumes possibly containing small amounts of ash rose to altitudes of 6.3-7.2 km (20,700-23,600 ft) a.s.l. during 15 and 17-18 April and drifted in multiple directions. Based on pilot reports, satellite imagery, and observations in the Petropavlovsk-Kamchatsky Flight Information Region (FIR), the Tokyo VAAC reported several E-drifting ash plumes. They rose to altitudes of 5.2 (17,000 ft) a.s.l. and 8.8 km (29,000 ft) on 18 and 22 April, respectively. On 24 April, KVERT reported mudflows and phreatic activity at lava flow fronts on the NW flank. Resultant ash plumes rose from the lava flow fronts to an altitude of 3.5 km (11,500 ft) a.s.l. The Level of Concern Color Code remained at Orange
During 18-24 April, lava from Kilauea continued to flow SE across a lava delta into the ocean at the Kamokuna entry, but lava was not seen entering the ocean at East Lae'apuki. Incandescence was intermittently visible from several breakouts on the Pulama pali and from several vents in the Pu'u 'O'o crater. Earthquake activity was scattered at the summit and S-flank areas. Tremor remained at moderate levels.