The PHIVOLCS volcano observatory reported that an increased number of rock falls have emanated from the summit lava dome since April.
This likely signalise pressurized magma within the main conduit system, which may fracture and squeeze surroundings rocks allowing it to rise further. Thus, fresh magma may accumulate into the lava dome in the inner summit crater, and more and more unstable hot lava material is prone to collapse into glowing dome avalanches. Another reason for this activity might be volcanic gases trapped beneath/within the viscous lava dome, which may lead to phreatic or hydrothermal explosion. Phreatic explosions form when the ejecta consist solely of old country rock, indicating interaction between water and heated conduit-rocks rather than magma itself.
Glowing lava blocks frequency increased from 5 events per day to 49 events per day during 4 and 5 June. 318 rock fall events have been registered since 1 April.
As of 9 May, the lava dome volume raised by 83,000 m3 since 3 February with a total volume of 164,000 m3 measured since 20 August 2022.
A short-term electronic tilt monitoring recorded the upper slopes inflated since February, which may indicate volcanic gases and/or magma reaching shallow levels, another tell-tale sign of an impending eruption However, the long-term ground deformation suggests the ongoing uplifting of the edifice, on the northwestern and southeastern slopes in particular, since 2020.
Sulfur dioxide (SO2) emissions reached to a 162 tonnes/day on average on 23 May.
Therefore, the alert level for the volcano was raised to Level 2 (increasing unrest).
In order to mitigate the risk, people are forbidden to enter an area of 6 km distance from the summit crater due to impacts of rockfalls, pyroclastic falls and/or phreatic eruptions.
Source: Philippine Institute of Volcanology and Seismology volcano activity update 6 June 2023