The activity of the Sirung volcano saw an increase which was observed visually from the phreatic eruption that occurred on July 21, 2021 from 4:44 p.m. WITA to approximately 6:00 p.m. WITA, which emitted white-gray gas and ash with light to medium intensity. The maximum height of the plume reached about 2000 meters above the summit, with a dominant direction to the north.
The increase in the amplitude of the tremor lasted about 10 hours on July 21, 2021 before the ash was released, but volcanic earthquakes indicating movement of magma from the depth were not recorded and the amplitude of the tremor did not show a significant increase.
The phreatic eruption that occurred was the result of the interaction between the heat of the magma and the hydrothermal system of Mount Sirung.
Mount Sirung's activity level was raised to Level II (waspada) on July 21, 2021 at 9:00 p.m. WITA, along with a VONA Orange issued by VAAC Darwin.
It is recommended that the community around Mount Sirung as well as visitors / climbers / tourists not perform activities within 1.5 km of the summit / crater of Mount Sirung.
The last (phreatic) eruption of Sirung dates from May 8 and 12, 2012.
Sirung volcano is located at the northeast end of a 14 km line of volcanic centers that form a peninsula at the southern end of Pantar Island. The volcano is truncated by a 2 km wide caldera, the soil of which often contains one or more small lakes. Much of the volcano is made up of basaltic lava flows, and the lava dome of Gunung Sirung forms the highest point on the western edge of the caldera.
Source: PVMBG & VAAC Darwin, GVP
On Tuesday July 20, at 4:38 p.m. local time (8:38 p.m. UTC), monitoring stations installed near the Nevados de Chillán volcanic complex recorded an earthquake associated with fluid dynamics (long period type) in the volcanic system. A plume of ash and gas was emitted up to 560 m above the point of emission.
On July 21, a similar earthquake occurred, with the emission of a plume 300 m high. above the crater.
Nevado del Ruiz activity during the week of July 13 to 19:
Seismicity linked to fluid dynamics, inside volcanic conduits, increased in number of events and in seismic energy released compared to the previous week. This seismic activity was characterized by the appearance of continuous volcanic tremor, tremor pulses, long and very long period earthquakes, which exhibited varying energy levels and spectral content. The earthquakes were located mainly in the Arenas crater. Some of these signals were associated with ash emissions.
Seismicity generated by rock fracturing increased in number of earthquakes and seismic energy released, compared to the previous week. This seismic activity was localized mainly in the south-southwest sectors and the Arenas crater, to a lesser extent in the southwest, northeast and distal north sectors of the volcano. The depths of the earthquakes ranged from 0.4 to 5.5 km. An increase in this type of seismicity emerged on July 14, the earthquakes were located about 3.3 km southwest of the Arenas crater at depths that varied between 2.8 and 4.2 km. The maximum magnitude recorded during the week and, in turn, the largest of the increase was 1.8 ML (local magnitude), corresponding to the earthquake recorded on July 14 at 09:41 (local time), located at 3 , 6 km south-southwest of the Arenas crater at 3.7 km deep.
Regarding drumbeat-type seismicity, there were several low energy episodes associated with rock fracturing on July 13, 14 and 17. This seismicity has been linked to the processes of ascent, location-growth and evolution of a lava dome1 at the bottom of the Arenas crater.
The deformation of the volcanic surface, measured from GNSS (Global Navigation Satellite System) stations and electronic inclinometers continued to show minor changes.
The volcano continues to emit water vapor and gases, mainly sulfur dioxide. The column of gas and vapor reached a maximum height of 1,098 m above the summit of the volcano on July 14. The dispersion of the column was governed by the direction of the wind, towards the west-northwest and west-southwest sectors of the volcano.
During the last week, the MIROVA and NASA FIRMS portals did not report thermal anomalies in the volcano area.
The Nevado del Ruiz volcano continues at the yellow activity level.
Source: Weekly activity bulletin of the Nevado del Ruiz volcano 13/07 / 19.07.2021 / Servicio Geologico Colombiano
Shallow, low-magnitude earthquakes continue to be recorded in Lake Kivu, following the Nyiragongo eruption in May 2021.
These earthquakes, respectively M 3.9 and 3.5, were recorded at a depth of about 5 km at 6:26 p.m. and 6:32 p.m. on July 21 (Rwanda Seismic Monitor)
Source: Dr. Charles Balagzi / Geochemistry and Environmantal Department, at Goma Volcano Observatory