Activity at Taal

[bjdeming]

Not sure when that long tremor finally broke, but it did so without an eruption.

Taal is still restless, though.

 

[bjdeming]

SO2 emission has dropped a bit, but:

...state volcanologists still detected 10 volcanic earthquakes, accompanied by eight volcanic tremors. The day before, the agency recorded five earthquakes and two tremors.


From September 1 to 8, Taal registered a total of 86 volcanic earthquakes and 78 volcanic tremors.

Phivolcs explained that volcanic earthquakes are caused by magma-related processes beneath an active volcano, distinguishing them from tectonic earthquakes, which result from fault movements. Volcanic tremors, meanwhile, are described as continuous seismic signals with low-frequency oscillations, typically lasting more than a minute.


During the latest monitoring period, no upwelling of hot volcanic fluids was observed in the main crater lake on TVI. No volcanic smog, or “vog,” was detected either.


Despite the continued seismic activity, Taal Volcano remains under Alert Level 1, which indicates low-level unrest. Phivolcs noted, however, that this does not mean the volcano has returned to normal and that eruptive activity remains possible...

-- Source

It seems to be holding. There have been periods of much higher gas emissions, as well as upwelling in Main Crater's lake out on Volcano Island -- and even thermal bursts.

However, the tremor, especially that long one that began at the end of August, is what this layperson focuses on most, and the volcanic quakes.

It's probably fluids (at that depth and temperature, some gases are fluids, too, but Taal has a LOT of water inside).

The boffins are keeping it at Level 1 alert.

 

[bjdeming]

News of minor phreatic plumes at Main Crater Lake. These are very, very mild but it is a change. Still Level 1 alert.

 

[bjdeming]

This layperson thinks it's a waiting game now, most likely for another massive explosion of the hydrothermal system when the caprock fails again, and there's no telling how long it will take to start. Things will happen fast after that, though.

Taal Volcano’s seismic energy release is still elevated, the head of the Philippine Institute of Volcanology and Seismology (Phivolcs) said on Friday.

The RSAM (real-time seismic amplitude measurement) of Taal Volcano has not returned to background level since a high seismic energy release was reported last month, Phivolcs Director Teresito Bacolcol said...

-- Source

 

[bjdeming]

No changes reported -- I just noted that up until August 3, PHIVOLCS reported long-term deflation of Taal Caldera as well as inflation of the west and southwestern flanks of Volcano Island.

Starting September 1, that changed to a report of short-term inflation of Volcano Island, which continues to be reported.

While looking that up I learned that on September 3rd they announced the end of the tremor episode that began August 27 and had a run of 7 days, 12 hours, and 26 minutes.

So, still, waiting game. <Layperson speculation> And maybe a magma-driven eruption can be included on the possibilities list, along with the aforementioned possibility of a repeat explosion of the hydrothermal system. </Layperson speculation>

We needn't get concerned over the caldera. That is on a whole 'nother level and presumably will have big precursors long before it ever fires up again.

Ordinary volcanism and Volcano Island are the main things to look out for.

We've seen what a hydrothermal system explosion looks like here, and fortunately its force was directed mostly upwards, not outward to create major tsunamis on the lake.

More layperson speculation: In a magmatic eruption, I think that because of various gas and phreatic blast forces and vent topography, sideways explosions can occur (especially if it's a submarine eruption, which has occurred at Taal, too).

Then it's tsunami and possibly even base surge time. Unfortunately, both of these have happened here, too, and were deadly.

Sometimes there have been larger (but not caldera-forming) eruptions, too. For an idea about those, well, Taal Lake used to be an ocean bay. Just one eruption out on Volcano Island -- can't look it up now, but I think it was a VEI 4 -- blocked it off from the sea, and thanks to the region's high rainfall, it became a freshwater lake.

This was just a few centuries ago.