Eruptions

KVERT reported that a weak thermal anomaly over Karymsky was visible in satellite images during 18-21 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 there were 19 events during 22-28 April recorded by Anak Krakatau?s seismic network; no emissions from the events were visually observed, even though the visibility was a mix of clear and foggy conditions. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to remain outside of the 2-km radius hazard zone from the crater.

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

PVMBG reported that during 22-28 April the lava dome at Merapi continued to grow slowly, with any extruded material channeled into the SE-flank Gendol River drainage. White emissions rose 70 m. Five block-and-ash flows traveled as far as 1.2 km in the Gendol drainage on 24 April. 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.

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

SERNAGEOMIN reported that the lava dome in Nevados de Chillán?s Nicanor Crater continued a cycle of slow growth and partial destruction from explosions during 23-30 April. The pulsating, generally white, emissions were sometimes gray and rose no higher than 900 m above the crater rim and drifted NW, S, and SE. Nighttime webcam data showed incandescent ejecta around the crater. The Alert Level remained at Orange, the second highest level on a four-color scale, and residents were reminded not to approach the crater within 3 km. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián.

Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN)

OVSICORI-UNA reported that on 24 April a very diffuse ash emission rose from Poás. Incandescence from vent A (Boca Roja) was sometimes visible during 24 and 27-28 April.

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

IG reported that during 23-30 April periodic seismic data from Reventador?s network indicated a high level of seismic activity, including explosions, long-period earthquakes, harmonic tremor, and signals indicating emissions. Steam, gas, and ash plumes sometimes rose higher than 1 km above the crater rim and drifted N, NW, W, and SW. Incandescent blocks were observed rolling 500-800 m down the flanks. Inclement weather sometimes prevented visual observations.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG)

GeoNet reported that the period of high water temperatures at Ruapehu?s summit Crater Lake along with elevated tremor levels was over. Tremor levels began to decline on 16 April and by 29 April was described as weak. The lake water reached a peak temperature of 44 degrees Celsius on 19 April and then began cooling; the temperature was 39 degrees Celsius by 29 April. The report noted that the probability of an eruption during a heating cycle had decreased with the decreasing activity. The Volcanic Alert Level remained at 1 (minor volcanic unrest) and the Aviation Color Code remained at Green.

Source: GeoNet

KVERT reported that a thermal anomaly over Sheveluch?s lava dome was identified daily in satellite images during 18-26 April. Ash plumes were visible drifting 300 km NE during 22-23 April. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

OVSICORI-UNA reported that a diffuse ash emission rose from Turrialba on 24 April, and an emission with low ash content drifted N on 26 April. At 0722 on 27 April a small, short-duration eruption generated an ash plume that rose less than 100 m above the crater rim.

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

On 30 April AVO lowered the Aviation Color Code for Veniaminof to Green and the Volcano Alert Level to Normal, noting that signs of unrest had continued to decline over the previous four months since the eruption ended in early January. Low-level tremor, slightly elevated surface temperatures, and minor steam emissions continued and considered typical activity for a post-eruptive period.

Source: US Geological Survey Alaska Volcano Observatory (AVO)