AVO reported that elevated surface temperatures were observed over Cleveland in satellite imagery during 11-12 April. Two explosions were detected on 13 April by distant seismic stations and infrasound arrays. Neither of these explosions produced an ash cloud that could be detected in satellite images. There was no evidence of explosive activity or eruption of lava in the summit crater during 14-17 April. No seismic information was available because Cleveland does not have a real-time seismic network.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

CENAPRED reported that during 11-15 April steam-and-gas emissions from Popocatépetl occasionally contained ash; emissions contained a substantial amount of ash on 12 April. Seismicity increased on 13 April and at 2220 an explosion ejected incandescent blocks that landed on the NE flank as far as 500 m away from the crater rim. A larger explosion at 2236 ejected incandescent blocks that landed even further away on all flanks; an ash plume rose 2 km above the crater and drifted ENE. Ashfall was reported in San Pedro Benito Juarez (10-12 km SE), where the explosion was also heard. On 14 April gas-and-steam plumes that contained small amounts of ash drifted SW. Multiple emissions occurred with increased incandescence from the crater. Ejected incandescent blocks landed back in the crater or on the flanks 500-800 m from the rim. Gas-and-ash plumes drifted ESE. Ashfall was reported in multiple towns, including Puebla (50 km to the E), San Pedro Benito Juarez, Santiago Xalitzintla (15 km NE), Tianguismanalco, and Atlixco (25 km SE).

On 15 April an ash plume rose 1.5 km above the crater and drifted E. Gas-and-ash emissions rose 1 km above the crater on 16 April and were accompanied by ejected incandescent fragments that were deposited on the flanks, especially to the N and NE. Later that day ash plumes rose 2 km above the crater and drifted E. Ashfall was again reported in Puebla. CENAPRED increased the Alert Level at the volcano from Yellow Phase Two to Yellow Phase Three. During 16-17 April incandescence extended 300 m above the crater and gas-and-steam emissions were constant. Gas-and-ash plumes rose from the crater on 17 April.

Source: Centro Nacional de Prevencion de Desastres (CENAPRED)

OVSICORI-UNA reported that a small phreatic eruption occurred within and around the hot acidic lake of Rincon de la Vieja at 1400 on 14 April. Observers from nearby communities N of the volcano reported some sediment deposition along the outer N flanks of the main active crater and a white steam plume rising to a considerable height above the crater.

Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)

On 6, 8, and 10 April a visitor to Sakura-jima observed and photographed several Vulcanian explosions from Showa crater and noted that the crater was approximately 20% wider from N to S that in the beginning of 2010.

Source: Richard Roscoe, Photo Volcanica

Sezione di Catania - Osservatorio Etneo reported that the twenty-fourth paroxysmal eruptive episode since January 2011 took place at New SE Crater (New SEC) of Etna during the morning of 12 April following about 10 days of quiescence. The episode was characterized by lava fountains, emissions of ash and lapilli, and lava flows that descended the Valle del Bove and explosively interacted with snow cover.

Source: Sezione di Catania - Osservatorio Etneo (INGV)

KVERT reported that during 7-13 April moderate seismic activity from Karymsky continued to be detected, and indicated that possible ash plumes rose to an altitude of 2.5 km (8,200 ft) a.s.l. Satellite imagery showed a thermal anomaly on the volcano during 7 and 9-10 April, and ash deposits 15 km long on the E flank on 11 April. The Aviation Color Code remained at Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

During 11-17 April HVO reported that the circulating lava lake periodically rose and fell in the deep pit within Kīlauea's Halemaʻumaʻu Crater. Almost daily measurements indicated that the gas plume from the vent continued to deposit variable amounts of ash, and occasionally fresh spatter, nearby. Incandescence was visible from both a lava pond in a small pit on the E edge and a small spatter cone on the SE edge of the Puʻu ʻŌʻō crater floor, and on the upper part of the lava-tube system on the E flank. Lava flows continued to advance down the pali and across the coastal plain, reaching about 1.4 km from the coast. On 11 and 13 April small lava flows issued from a vent on the SE edge of the Puʻu ʻŌʻō crater floor.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that seismicity at Nevado del Ruiz decreased during 11-15 April then slightly increased during 16-17 April. Earthquakes were located below or N of Arenas crater at depths of 1.5-2 km during 11-12 April. Earthquake events at 1146 and 1149 on 15 April were possibly associated with ash emissions which were not verified due to weather conditions. Earthquakes detected on 16 April occurred E of Arenas crater at depths of 1.5-4 km.

Gas-and-steam plumes were observed mainly in satellite imagery, by cameras located near the volcano, and from the city of Manizales (25 km NW). On 12 April a sulfur odor was reported in the towns of Lebanon, Palocabildo, and Fresno (Tolima). Observes in Manila reported a gas-and-steam plume that rose 1.8 km above the crater on 16 April. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)

Minor steam-and-gas plumes from Pagan were observed in satellite images during clear periods from 6 to 13 April. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory. According to the Washington VAAC satellite images showed a plume that drifted N. Satellite images and pilot reports indicated no ash in the plume. Emissions to the W had become diffuse.

Sources: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program, Washington Volcanic Ash Advisory Center (VAAC)

OVDAS-SERNAGEOMIN reported that, although cloud cover often prevented observations during 11-17 April, satellite and web camera views of the Cordón Caulle rift zone, part of the Puyehue-Cordón Caulle volcanic complex, showed plumes almost daily that rose no higher than 1 km above the crater. Incandescence from the crater was observed during 10-11 April. The Alert Level remained at Orange.

Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN)

KVERT reported that explosive activity at Shiveluch continued during 7-13 April. Ground-based observers and satellite imagery indicated that a viscous lava flow continued to effuse in the crater formed during a 2010 eruption. Satellite imagery showed a weak thermal anomaly daily on the lava dome, and ash plumes that drifted 210 km SW and SE on 6, 8, and 11 April. Seismic data indicated that ash plumes potentially rose to an altitude of 7.7 km (25,000 ft) a.s.l. during 7-8 and 10-12 April, and to an altitude of 4.5 km (14,800 ft) a.s.l. on the other days. Observers confirmed that an ash plume rose to an altitude of 5 km (16,400 ft) a.s.l. on 8 April. The Aviation Color Code remained at Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

IG reported that during 11-15 April visual observations of Tungurahua were occasionally limited due to cloud cover. On 11 April an ash plume rose 5 km above the crater and drifted NE and SE. Ashfall was reported in areas 8 km SW. An explosion on 12 April was followed by ashfall in multiple areas including Ambato (31 km NW), Cusúa (8 km NW), and Bilbao (8 km W). A small ash plume drifted ESE on 13 April and steam plumes drifted SE during 13-14 April. Fumarolic activity in the crater was observed on 15 April.

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

According to Projecto Observación Visual Volcán Villarrica (POVI), ash emissions rose from Villarrica on 9 April and incandescence emanated from the crater at night.

Source: Proyecto Observación Villarrica Internet (POVI)