Attachments
1) Summary of Activity:
The Alert Level 3 (Increased Tendency Towards Hazardous Eruption) was raised on 12:00 noon of **8 June 2023 **after small-volume pyroclastic density currents or PDCs began generating from Mayon Volcano’s summit lava dome, signalling the start of effusive magmatic eruption. Repeated spalling and collapse generated incandescent rockfall and PDCs mainly in the Mi-isi (south) and Bonga (southeastern) Gullies within one to two kilometers of the summit crater. By the early morning of 10 June, the pre-eruption lava dome had been completely shed and, in its place, a newly-extruded dark lava dome emerged higher than the crater rim, impinged on its southeast by remnant dome lava from an earlier phase of extrusion. Volcanic SO2 briefly increased two-fold to 1,205 tonnes/day on the same day. At 7:47 PM of 11 June, lava flow effusion from the eastern and central margins of the lava dome commenced and formed two very slowly advancing lobes on the Mi-isi and Bonga Gullies. This event was preceded earlier in the day by a small but detectable inflation of the middle and upper slopes recorded by electronic tilt arrays on the southeast and northwest flanks of the volcano. Lava effusion marked the beginning of increased rockfall and PDCs that were mainly generated by lava collapse from the summit crater, as well as of incremental minor increases in seismic energy release. SO2 emission also slightly increased beyond background levels of 500 tonnes/day, but still remained well below past eruption records of several thousand tonnes per day. Volcanic earthquakes also slightly increased in incidence but remained very weak.
Rockfall events peaked to around 300/day between 14 and 16 June, while PDCs peaked to 13 events on 15 June. The largest PDC occurred for six (6) minutes at 11:18 PM on 15 June and involved the collapse of the remnant summit lava dome based on its absence in photos of the crater the next day. A PDC runout of 3.3 kilometers can be assumed from the noticeable advance of debris on Mi-isi Gully by 16 June. Thin ashfall from the 15 July PDCs was reported in Sitio Buga, Brgy. Nabonton, Ligao City and Purok 7, Brgy. San Francisco, Guinobatan. Lava flows had advanced to 1.5 kilometers aerial distance from the crater on the Mi-isi Gully by 16 June and on the Bonga Gully by 18 June, at very slow average flow rates of 250-350 meters/day on the steep upper volcanic slopes.
Summary plots: Daily (A) rockfall and (B) PDC or pyroclastic density current events in bars with red lines indicating five-day moving averages. Day corresponds to 24-hour observation period from 5AM of previous day to 5AM of reporting day. (C) Sesimic energy release, in real-time seismic amplitudes or RSAM, from the Anoling, Camalig Station (VMAN), showing a slightly increasing trend after lava effusion from the summit begins. Spikes correspond to rockfall, PDC, volcanic and tectonic earthquake events. (D) Average SO2 emission with bars of standard deviation. Slight increases beyond baseline or background levels have been recorded since 10 June 2023.
2) Current Outlook:
Low-rate effusive eruption of degassed lava has been transpiring for the past week accompanied only by slight increases in volcanic SO2 emission, seismic and ground deformation parameters. The very low mass eruption rate generates sluggish lava flows and intermittent collapse of the summit lava dome and lava flow margins that feed frequent rockfall and occasional small-volume PDCs within the Permanent Danger Zone. This state of unrest is largely similar to Mayon’s 2014 eruption and may persist for a few months. Alert Level 3 is maintained. The volcano’s condition, however, may change any time and may progress into the following eruption scenarios given the corresponding changes in monitored parameters:
a) Slow and sustained lava extrusion (e.g. 2006 eruption), if apparent rates of extrusion increase, SO2 emission increases persist and seismic activity (e.g. low-level tremor) and a cycle of inflation (swelling) and deflation (unswelling) of the edifice occur. Activity may last for a few months. Alert Level 4 will be raised.a) Slow and sustained lava extrusion (e.g. 2006 eruption), if apparent rates of extrusion increase, SO2 emission increases persist and seismic activity (e.g. low-level tremor) and a cycle of inflation (swelling) and deflation (unswelling) of the edifice occur. Activity may last for a few months. Alert Level 4 will be raised.
b) Lava fountaining and lava flow with occasional explosions and PDCs within the 6km-PDZ (e.g. 2018 eruption), if significant increases in SO2 emission, increased seismicity (low-frequency and tremor events) and inflation (swelling) of the entire edifice occur. Activity may last for a few months. Alert Level 4 will be raised.
c) Explosive eruption with high-intensity lava fountaining, long lava flows and PDCs on all sectors that could exceed the 6km-PDZ (e.g. 2000 eruption), if rapid escalation in SO2 (or sudden drop), volcanic earthquake activity and ground deformation occur. Activity may last for a few days to weeks. Alert Level 5 will be raised.
3) Recommendations:
Evacuation of the **Six-Kilometer Radius Permanent Danger Zone (PDZ) **is recommended at Alert Level 3. For the complete list of barangays with areas within the PDZ, please refer to Volcano Activity Report of 10 June 2023.
Local government units, disaster officials and the general public are urged to heed avoidance of the PDZ, as the summit lava dome has grown above and filled up the summit crater, increasing the chances of lava collapse or potential volcanic flows onto other sectors of the volcano.
For the latest information on Mayon Volcano, please download the VolcanoPH Info app from the Google Play Store and refer to these DOST-PHIVOLCS official accounts:
- Website: https://phivolcs.dost.gov.ph/
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