OVSICORI-UNA reported that on 24 May a series of incandescent flows descended the W flank, towards the lake, reaching the forest. An ash plume drifted N. Arenal National Park was closed briefly due to the activity.

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

KVERT reported that some earthquakes were detected in the vicinity of Bezymianny's lava dome during 23-24 May, even though much of the seismicity was obscured by strong activity from Kliuchevskoi. Fumarolic activity was seen on 21 May. The temperature of the thermal anomaly detected in satellite imagery increased from 18 degrees Celsius on 19 May to 48.8 degrees Celsius on 23 May. The Aviation Color Code level was raised to Orange. During 21-28 May satellite data showed a variable but daily thermal anomaly over the lava dome. Fumarolic activity was occasionally detected, and another seismic event was recorded on 24 May.

Seismic data indicated that an explosive eruption began on 1 June, producing a large ash cloud about 127 by 93 km in dimension. The Aviation Color Code level was raised to Red. Further analyses showed that ash plumes from two explosions rose to altitudes of 8-10 km (26,200-32,800 ft) a.s.l. and drifted at first 250 km W and then 160 km N and NE. Ashfall was reported in Kozyrevsk village, 45 km W. Two bright thermal anomalies were seen in satellite imagery, possibly from pyroclastic flow deposits. The next day, strong gas-and-steam emissions rose from the lava dome. The Aviation Color Code level was lowered to Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

AVO reported a small ash emission from Cleveland on 30 May. A detached plume seen in satellite imagery rose no higher than 4.9 km (16,000 ft) a.s.l. and drifted SW. Satellite images the next day revealed minor (uncharacterized) flow deposits on the upper flanks. The Volcano Alert Level remained at Advisory and the Aviation Color Code remained at Yellow.

Source: US Geological Survey Alaska Volcano Observatory (AVO)

According to JMA, a small eruption from Shinmoe-dake (Shinmoe peak), a stratovolcano of the Kirishima volcano group, on 27 May produced an ash plume that rose 100 m above the crater rim. Ashfall was noted in areas within 6 km. Emissions gradually decreased.

Source: Japan Meteorological Agency (JMA)

A Strombolian eruption from Pacaya's MacKenney cone that began on 27 May was characterized in a report from CONRED as having constant explosions that ejected material 500 m into the air. Ash plumes rose 1.5 km above the crater and drifted W and SW, causing ashfall in multiple areas. The community of El Patrocinio (about 5 km W) evacuated and residents in El Rodeo (4 km WSW) were ordered to evacuate. Due to extensive tephra fall, authorities recommended that residents clean off ash from their roofs and refrain from driving.

INSIVUMEH reported a continuing series of explosions 5-10 seconds apart that ejected black ash up to 1 km above the crater on 28 May. Seismic signals reflected the explosions in addition to tremor. Ash plumes drifted 20-30 km NW, causing ashfall in areas downwind, including in Guatemala City, about 30 km NNE. CONRED reported a short time later that about 1,600 people had been evacuated from six towns 3-4 km W, NNW, N, and NNE, and that Aurora International Airport was closed. According to a map posted by CONRED, blocks fell in areas as far away as 12 km NE and ash was reported in areas E of Chinautla, 37 km NNE. News media reported that one person (a reporter) died and three children were missing.

On 29 May, a 90-m-wide lava flow that traveled SSE at an estimated rate of 100 m per hour burned three houses on the Pacaya Grande ranch. The lava was within 450 m of some other properties including El Chupadero, located 2-2.5 km S of the crater, and disrupted an access road from El Caracol (3 km SW) and Los Pocitos (5.5 km S). Explosions ejected ash 300-500 m above the crater. INSIVUMEH reported on 1 June that the Strombolian activity continued. Explosions ejected ash as high as 700 m above the crater and ash plumes drifted NW. Two lava flows were seen traveling SW and SE.

Sources: Reuters, Coordinadora Nacional para la Reducción de Desastres (CONRED), Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)

Gas-and-steam plumes from Pagan continued to be observed in satellite imagery during 21-28 May. Reports from researchers camped on the island, and imagery analyses, suggested that trace amounts of ash were intermittently present in the plumes during 23-26 May. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory.

Source: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program

On 27 May an observer from the Emergency Management Office (EMO) in Saipan photographed an area of discolored ocean water and possible light-colored floating material about 7 km S of Sarigan during an overflight. The area was about 1.6 km long, although the scale was difficult to discern from photographs. Two days later, the area of affected water was about twice the size of Sarigan Island. According to a news article, U.S. Fish and Wildlife evacuated 16 people, mostly scientists, to Saipan from a few area islands, including eight people from Sarigan.

On 30 May a plume of mostly water vapor was seen in satellite imagery rising to a possible altitude of 12.2 km (40,000 ft) a.s.l. and dissipating as it drifted S. The eruption was attributed to a 300-m-deep submarine vent on Sarigan's S flank, about 7 km from the island. Observers on Sarigan reported hearing a loud explosion from the S, and shortly thereafter received ashfall. The Volcano Alert Level was raised to Watch and the Aviation Color Code was raised to Orange. Both seismicity at a single nearby station on Sarigan and subaqueous activity declined after the plume emission. The next day the Volcano Alert Level was reduced to Advisory and the Aviation Color Code was reduced to Yellow.

Sources: Saipan Tribune, Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program

The IG reported that on 26 May a strong explosion from Tungurahua generated pyroclastic flows and an ash plume that rose to an altitude of 12 km (39,400 ft) a.s.l. and drifted W and SW. Ashfall was reported in areas to the S and SW, including Riobamba (30 km S). Noises resembling "cannon shots" associated with the explosion were heard as far away as Guadalupe, 11 km N. The pyroclastic flows were small and traveled 800-1,000 m down the N, NW, W, and SW flanks; they did not reach populated areas. Poor visibility mostly prevented observations of the crater the next day, but no activity was seen when the crater was visible. Slight ashfall was reported in Cahuají.

On 28 May another strong explosion produced an ash plume that rose to an altitude of 15 km (49,200 ft) a.s.l. and drifted WSW. Pumice blocks fell in local neighborhoods (likely 6-8 km away), and ash fell in several areas between Tungurahua and Guayaquil (about 180 km SW), and beyond. Pyroclastic flows traveled as far as 3 km down the NW, W, and SW flanks, but again did not reach populated areas. According to news articles, residents from two towns about 8 km NW were evacuated and the airport in Guayaquil was temporarily closed because the runways were covered in ash. Other flights passing through the area were rerouted.

During 28-29 May seismicity increased and 5-10 explosions were detected per hour. Explosions ejected incandescent blocks that fell 1-2 km below the summit. Ashfall was heavy in Runtún, 6 km NNE, at night on 28 May, and lighter in Juive and Puntzán, 7 km NW, the next morning. During 29-30 May explosions occurred at a rate of about 10 per hour. Several roaring noises were noted and "cannon shot" noises caused large windows nearby to vibrate. Incandescence around the crater was seen occasionally at night, during periods of clearer viewing. On 31 May and 1 June explosions generated audible "cannon shots" and ejected incandescent blocks as high as 1.5 km above the crater rim; several of the blocks rolled nearly 1 km down the flanks. Steam-and-ash plumes rose to altitudes of 7-9 km (23,000-29,500 ft) a.s.l. and drifted W, SW, N, and NE, causing ashfall in areas downwind.

Sources: Reuters, Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)

RVO reported that during 22-28 May Ulawun emitted thick white vapor plumes that rose 800 m high. Some areas of the plumes were gray on 22 and 25 May. People on the S and SE sides of the island heard "low jetting" noises during 24-25 May. Weak and fluctuating incandescence was seen at night during 28-29 May by people on the S part of the island. The emissions changed color to gray on 29 May and continued similarly the next two days. On 30 May very fine ashfall was reported in areas to the SSW, S, and SSE. On 1 and 2 June only white vapor emissions were noted. RVO recommended to the WNB Provincial Disaster Committee to declare a Stage 1 Alert to reflect an increasing trend of seismic energy, and a recent presence of occasional gray plumes, incandescence, and audible noises from Ulawun.

Source: Rabaul Volcano Observatory (RVO)

The Vanuatu Geohazards Observatory reported that the Vanuatu Volcano Alert Level (VVAL) for Yasur was increased to 3 (on a scale of 0-4) on 27 May. Recent activity was characterized by moderate to large eruptions with strong explosions, ejected bombs that fell on the visitor viewing area, and significant ashfall in nearby villages. Visitors were not allowed to enter a restricted zone, within about 500 m around the volcano. Activity had been escalating since January 2010. According to a news article, an eruption plume on 1 June rose to an altitude of 1.8 km (6,000 ft) a.s.l. and spread over 340 square kilometers, canceling or delaying some flights in and out of New Caledonia (about 430 km WSW).

Sources: Vanuatu Meteorology and Geohazards Department (VMGD), Notimex, Agence France-Presse (AFP)

KVERT reported that on 23 May a gas-and-steam plume from Alaid was seen in satellite imagery drifting 11 km ESE. No other signs of possible increasing activity were seen in imagery or noted by observers on Paramushir Island during 21-28 May. KVERT lowered the Aviation Color Code to Green.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

Based on analyses of satellite imagery, the Darwin VAAC reported that ash plumes from Bagana rose to an altitude of 3 km (10,000 ft) a.s.l. during 26-28 May and drifted 30-185 km SW and W.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)

The Nordic Volcanological Center (NVC) at the Institute of Earth Sciences reported that on 26 May steam plumes from Eyjafjallajökull rose to an altitude of 2 km (6,600 ft) a.s.l. and drifted S. The crater was not seen through the web cameras due to poor visibility from remobilized, blowing ash. Scientists conducted an expedition to the summit crater the next day. They measured the tephra deposits around the E half of the craters, and found that they were about 40 m thick closest to the craters. Steam rose from the crater, punctuated by a few small ash-bearing explosions, and a sulfur odor was strong nearby. On 31 May and 1 June, widespread drifting of existing ash was noted in SW Iceland. Meteorological clouds prevented views of the summit craters.

Source: Institute of Earth Sciences

INSIVUMEH reported on 29 May that abundant rains from tropical storm Agatha triggered lahars in ravines to Fuego's SW and SE.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)

Based on information from the Vanuatu Geohazards Observatory, the Wellington VAAC reported that on 26 May an ash plume from Gaua rose to an altitude of 3 km (10,000 ft) a.s.l.

Source: Wellington Volcanic Ash Advisory Center (VAAC)

KVERT reported that during 21-28 May seismic activity from Karymsky was above background levels, suggesting that possible ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. Satellite imagery revealed a daily thermal anomaly over the volcano, and ash plumes that drifted 63 km S and W during 24-26 May. The Aviation Color Code level remained at Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

During 26 May-1 June HVO reported that activity at Kīlauea continued from the summit and the east rift zone. At the summit, the level of the circulating, crusting, and bubbling lava-pool surface remained mostly stable in the deep pit inset within the floor of Halemaʻumaʻu crater; glow from the vent was visible. On 31 May the surface rose to the highest level yet recorded, but was still more than 100 m below the Halemaʻumaʻu crater floor.

At the east rift zone, lava flows that broke out of the TEB lava-tube system had advanced down the Pūlama pali onto the coastal plain and headed S, entering the ocean at Ki. Other lava flows were active above the pali. On 27 May geologists noted a small rootless shield building up at a break-out point at 580 m elevation. Small lava flows issued from vents on Puʻu ʻŌʻō's S crater wall during 26-27 May, and pooled on the crater floor at least through 31 May.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

KVERT reported that during 21-28 May seismic activity from Kliuchevskoi was above background levels and Strombolian activity was seen. Gas-and-steam plumes occasionally containing a small amount of ash were also noted. During 23-26 May observed ash plumes rose to an altitude of 5.5 km (18,000 ft) a.s.l. Satellite imagery revealed a large daily thermal anomaly from the volcano, and ash plumes that drifted 185 km in multiple directions on 24 and 26 May. The Aviation Color Code level remained at Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

The IG reported a lahar on Reventador's E flank, detected for 90 minutes by the seismic network on 25 May. It destroyed a bridge over the Marker River, disrupting the route from Baeza to Lago Agrio.

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

INSIVUMEH reported on 29 May that abundant rains from tropical storm Agatha triggered lahars in Santa Maria's S ravines.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)

SVERT reported that a thermal anomaly on Sarychev Peak was detected by satellite on 27 May. Sarychev Peak does not have a seismic network; satellite image observations are the primary tool for monitoring many of the Kurile Islands volcanoes.

Source: Sakhalin Volcanic Eruption Response Team (SVERT)

KVERT reported that during 21-28 May seismic activity from Shiveluch was above background levels, suggesting that possible ash plumes rose to an altitude of 4.7 km (15,400 ft) a.s.l. Satellite imagery showed a large daily thermal anomaly, and an ash plume that drifted 10 km NE on 23 May. Observations revealed fumarolic activity, and ash plumes that rose to an altitude of 4.5 km (14,800 ft) a.s.l. on 24 and 25 May. The Aviation Color Code level remained at Orange.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)