Roundup of Global Volcanic Activity – New Activity for the week of 3 May – 9 May 2023
Bulusan – Luzon (Philippines) : PHIVOLCS reported that during 7-9 May the seismic network at Bulusan recorded a total of 17 volcanic earthquakes at depths of 0-5.2 km beneath the E flank. Six of the earthquakes were tornillo-type events associated with gas movement and the other 11 events were volcano-tectonic earthquakes associated with rock fracturing. Diffuse white steam plumes rose from the active vents in the summit crater.
Fuego – South-Central Guatemala : INSIVUMEH reported that activity at Fuego during 2-9 May included intense explosions, dense ash emissions, lava effusion, pyroclastic flows, and lahars. During 1-3 May there were 5-8 weak explosions per hour generating dense ash plumes that rose more than 1 km above the summit and drifted to 10-15 km W, SW, and S. Explosions were accompanied by rumbling sounds and shockwaves that vibrated nearby houses. During the morning and night incandescent material was visible 100-200 m above the crater. Avalanches descended the Ceniza (SSW) and Las Lajas (SE) drainages, sometimes reaching vegetated areas. Ashfall was reported in areas downwind including Panimache I and II (8 km SW), Morelia (9 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), Finca Palo Verde, Sangre de Cristo (8 km WSW), and Yepocapa (8 km N). In the early afternoon (around 1500) on 2 May lahars descended the Las Lajas and El Jute (ESE) drainages, carrying branches, tree trunks, and blocks 30 cm to 1.5 m in diameter; about 30 minutes later similar lahars descended the Ceniza drainage. At 1618 a weak-to-moderate pyroclastic flow traveled down the Ceniza and an associated ash plume drifted W and SW. Within 30 minutes after the pyroclastic flow a lahar descended the Seca (W), carrying tree trunks and branches, and blocks up to 1.5 m in diameter. Activity intensified at around 0200 on 4 May with a new effusive phase; by 0510 a lava flow was traveling down the Ceniza drainage, incandescent material rose above the summit, avalanches were continuous, and ash-and-gas plumes drifted SW. At around 0700 weak-to-moderate pyroclastic flows descended the Ceniza and within 1.5 hours pyroclastic flows also descended the Las Lajas. Ashfall was reported on W-flank farms and communities including Finca La Asunción, La Rochela, Panimaché I and II, Morelia, Santa Sofía, as well as others at a greater distance such as San Rafael Sumatán (19 km WSW) and San Pedro Yepocapa. By 1000 moderate-to-strong pyroclastic flows were descending the W-flank Seca and Santa Teresa ravines. Loud rumbling sounds and shock waves were reported by local residents. Ashfall continued in communities near the Ceniza and Las Lajas ravines. Ash plumes rose 2.2 km above summit and drifted more than 50 km W and SW. Activity continued at a high level and as of a special report posted at 1235 ash plumes were still rising more than 2.2 m above the summit. Pyroclastic flows were continuing and had traveled 5-7 km down the Ceniza, Las Lajas, Seca and Santa Teresa (W) drainages; the most intense pyroclastic flow had descended the Ceniza drainage minutes earlier. The ash plumes were identified in satellite images drifting more than 100 km W and SW. Significant ashfall continued in communities downwind and minor ashfall was reported in several municipalities of the department of Suchitepéquez. The last pyroclastic flow descended the Ceniza at 1530. Avalanches continued to be seen and heard descending multiple flanks. Ash deposits up to 2 mm thick were noted on crops, houses, and streets. Activity began to wane at about 1800, though explosions continued to produce ash plumes that rose 1.2 km above the summit. The leading edge of the ash plume was 200 km W and SW of the volcano. According to CONRED, about 1,200 residents were preemptively evacuated from their homes in San Pedro Yepocapa, Chimaltenango (21 km NNE), Panimaché I and II, El Porvenir, and Morelia. According to news articles, a section of the RN-14 highway was closed from kilometer 84 of San Juan Alotenango, Sacatepequez (9 km ENE) to kilometer 95 in Escuintla due to the pyroclastic flows. An estimated 130,000 people lived within areas exposed to ashfall. Activity during the morning of 5 May was characterized by some weak-to-moderate explosions, ash plumes that rose 850 m above the summit, crater incandescence, and ash in the air in communities around the Ceniza, Seca, and Las Lajas drainages. Ashfall continued to impact agriculture and infrastructure in Panimaché I, Morelia, Santa Sofía, La Rochela, Los Yucales, El Porvenir, Ceylon, Finca Asunción (12 km SW), Yepocapa, Santa Lucía Cotzumalguapa (22 km SW), Siquinalá (21 km SSW), and other nearby communities. By 1230 data from seismic and infrasound monitoring networks, webcam images, satellite data, and reports from observers in the field all indicated that activity had returned to normal levels. Weak explosions at a rate of 5-6 per hour produced minor ash plumes that rose as high as 850 m and drifted 30 km W. On 6 May weak explosion generated ash plumes that rose 750 m and drifted 10 km W and SW. The lava flow was no longer incandescent. According to a news report, residents returned to their communities that same day. During 7-9 May weak explosions continued to produce ash plumes that rose as high as 750 m above the summit and drifted W and SW. Minor avalanches descended the Ceniza and crater incandescence was occasionally observed.
Gamalama – Halmahera : PVMBG reported that the number of deep volcanic earthquakes at Gamalama increased during 1-3 May. The seismic network recorded 11 deep volcanic earthquakes on 1 May and 14 on 2 May. During 0000-0900 on 3 May the network recorded five deep volcanic earthquakes, one shallow volcanic earthquake, five events indicating emissions, and one low-frequency earthquake. Diffuse white gas-and-steam plumes rose as high as 100 m; typically, these emissions rose as high as 300 m. PVMBG noted that the most likely hazard would be a phreatic event that could ejected material within the 1.5-km radius, though ash may be carried farther.
Kadovar – Northeast of New Guinea : Based on satellite and wind model data, the Darwin VAAC reported that at 2040 on 6 May a discrete ash plume from Kadovar rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted W. The plume had dissipated by 2300.
Kanlaon – Philippines : PHIVOLCS issued a special notice for Kanlaon at 2030 on 4 May, noting increased seismicity and ground deformation, and ongoing elevated sulfur dioxide emissions. Ground deformation data from continuous GPS and electronic tilt data indicated short-term inflation of the lower and mid-flanks of the volcano since March, though during the second week of April inflation was pronounced at the SE mid-flank. Real-time, continuous gas monitoring of thermal springs on the N flank detected sulfur dioxide for the first time beginning in April. Sulfur dioxide emissions at the summit crater averaged 632 tonnes per day on 1 May, lower than the average of 1,099 tonnes per day measured the day before, but higher than the average of 124 tonnes per day emitted since March. The seismic network detected 20 shallow volcanic earthquakes (M 1.2-2.4) beneath the summit crater between 2225 on 3 May until 1600 on 4 May.
Katla – Iceland : Iceland Met Office (IMO) reported that an intense seismic swarm began at Katla at 0941 on 4 May with three earthquakes larger than M 4 occurring beneath the caldera within about 10 minutes. The Aviation Color Code was raised to Yellow, the second lowest level on a four-color scale. According to a news article the three largest events were magnitudes 4.8, 4.7, and 4.5, adjusted from previous estimates of 4.5, 4.3, and 4.2. The larger earthquakes were felt in Thórsmörk and by residents in areas S of Mýrdalsjökull glacier (the glacier that covers Katla). The intensity of the events decreased after noon, though smaller earthquakes continued. Seismicity had decreased significantly by the next day with only five events recorded during 0000-0915 on 5 May. In an update posted at 1140 the activity was described as normal. More than 40 earthquakes had been recorded during the previous day and no other data indicated significant changes or anomalies. It was noted that the magnitudes were unusually large and similar to events that last occurred in 2016.