Taal Unrest

July 24, 2021: PHIVOLCS has lowered things to alert level 2, so I’m going to unstick this from the front page, although Taal still is restive. Let’s see how things go.

Update, July 8, 2021, 9:49 a.m., Pacific: Something’s going on down there: weird how that tremor restarted minutes after the last small blast. Of note, Taal had a small blast a couple days ago but I didn’t blog it, since that’s to be expected in this scenario.

Multiple blasts and a change in seismicity (plus rise again in degassing) might indicate a change.


A series of five (5) short phreatomagmatic bursts occurred at 08:47 AM, 09:15 AM, 09:26 AM, 11:56 AM, and 09:41 PM yesterday and produced short jetted plumes that rose up to 700 meters above the Main Crater Lake.

In the past 24-hour period, the Taal Volcano Network recorded sixty-one (60) volcanic earthquakes, including five (5) explosion-type earthquakes, twenty-four (24) low frequency volcanic earthquakes, twenty-one (21) volcanic tremor events having durations of two (2) to four (4) minutes, ten (10) hybrid earthquakes, and low-level background tremor that ended yesterday at 06:21 PM but resumed at 09:52 PM. High levels of volcanic sulfur dioxide or SO2 gas emissions and steam-rich plumes that rose one thousand five hundred (1,500) meters before drifting southwest was generated from the Taal Main Crater. Sulfur dioxide (SO2) emission averaged 11,397 tonnes/day on 07 July 2021…


Update, July 5, 2021, 10:49 a.m., Pacific: Just found this interview with a PHIVOLCS spokesperson, posted about seven hours ago. Note that the “good” scenario is if the lake dries up!

The steaming is due to an upwelling of volcanic gas on the main crater lake of Taal Volcano, said Phivolcs officer-in-charge Renato Solidum.

“This means there’s a possibility that a similar phreatomagmatic eruption last Thursday may occur in Taal Volcano area,” he told ANC’s Headstart.

“The explosion can trigger pyroclastic density current that can move horizontally and move across lake water.”

Phivolcs could see a scenario where the eruption “might generate the base surge which can cross the waters and that can generate base surge on the mainland and volcanic tsunami,” according to Solidum. A base surge is a deadly lateral blast of hot gas, ash, and volcanic debris.

“It is also possible that when the lake water dries up, we can see if there will be continued eruption, there can be fountaining or fireworks of molten rocks and lava flow would ensue. That would be a better type of eruption because it will not be as dangerous,” he said.

“Of course at some point, the other scenario would be the volcano would cease to erupt.”

The volcano’s recent eruption and explosion last year were both phreatomagmatic but the former was de-gassed, Solidum said. Phreatomagmatic eruption is a result of new magma and water interacting.

“Last year, if people would recall during the height of the explosion, there were many earthquakes felt all over Batangas, even days and weeks after,” he said.

“This meant new magma has been resupplied from a sourceway below Balayan Bay diagonally moving up to the volcano. So there’s a resupply of new magma founded 4 to 5 kilometers below. That explains why there will still be some activities inside the volcano.”

USGS/J. G. Moore via Oregon State’s Volcano World

This is not a hypothetical situation.

Taal indeed had a surge/tsunami during an eruption on Volcano Island in 1965, which stripped these local trees. Check the Volcano World site link for more details.

Update, July 5, 2021, 7:29 a.m., Pacific: The sulfur degassing has doubled — and it was already insanely high. Am only a layperson, but this must indicate that there is a lot of magma near the surface. There isn’t a change in deformation or big uptick in seismicity reported, though, which is good. Lack of seismicity ordinarily would be worrisome (since volcanoes sometimes go quiet when they’re plugged and can’t relieve the pressure with a BOOM!), but the volcano is degassing through Volcano Island, relieving pressure that could otherwise build up to an explosive eruption.

That’s a HUGE amount of sulfur, though.

This amateur thinks that Taal is a very, very “sick” volcano right now. 😦

Emphasis added:


In the past 24-hour period, the Taal Volcano Network recorded seventeen (17) volcanic earthquakes, including one (1) volcanic tremor event having a duration of forty-five (45) minutes, sixteen (16) low frequency volcanic earthquakes, and low-level background tremor that has persisted since 08 April 2021. High levels of volcanic sulfur dioxide or SO2 gas emissions and steam-rich plumes that rose as much as two thousand five hundred (2,500) meters high that drifted southwest, southeast, and north-northwest was generated from the Taal Main Crater. Sulfur dioxide (SO2) emission averaged 22,628 tonnes/day on 04 July 2021. Based on ground deformation parameters from electronic tilt, continuous GPS and InSAR monitoring, Taal Volcano Island has begun deflating in April 2021 while the Taal region continues to undergo very slow extension since 2020…

Update, July 3, 2021, 1:43 a.m., Pacific:


A series of three (3) short phreatomagmatic bursts occurred at 10:25 AM, 10:47 AM, 11:01 AM yesterday and produced short jetted plumes that rose 100 meters above the Main Crater Lake. Active upwelling of hot volcanic fluids of the Taal Main Crater Lake followed in the afternoon.

In the past 24-hour period, the Taal Volcano Network recorded forty-eight (48) volcanic earthquakes, including two (2) volcano-tectonic earthquakes, forty (40) low frequency volcanic earthquakes, six (6) volcanic tremor events having durations up to four (4) minutes, and low-level background tremor that has persisted since 08 April 2021. High levels of volcanic sulfur dioxide or SO2 gas emissions and steam-rich plumes that rose as much as three thousand (3,000) meters high that drifted southwest and north-northwest were generated from the Taal Main Crater. Sulfur dioxide (SO2) emission averaged 10,254 tonnes/day on 02 July 2021. In addition, vog was observed over Taal Volcano and vicinity.


I don’t recall mention of vog in the 2020 activity reports. And that’s still a huge amount of sulfur emission.

By the way, there still seem to be some news reports describing Taal as a small volcano, so it’s worth mentioning again that what looks like a small volcano is actually the largest of a vent complex in the center of Taal Caldera.

The vent complex is called Volcano Island, because that’s what it looks like.

Taal is actually the surrounding caldera, which is very slightly larger than Taal Lake. It’s huge.

Per a recent news report:

Solidum explained these parameters indicate that the volcano is not yet calm.

Solidum said that since the magma in the shallower portion of the volcano has degassed, they do not expect it to cause a strong explosion as last year.

However, they need to monitor if there is new magma coming from the deeper portion of the volcano and carrying more gas which could cause a possible explosive eruption.

This was taken last year, about ten days after the big blast on Volcano Island. It shows some of that ash blowing in the wind. Fortunately for Manila (the urban area just north of Taal in this view), the caldera did not erupt in 2020, except a relatively little bit through Volcano Island. But remember, Taal Volcano is not just Volcano Island: it underlies Taal Lake plus a little of the shore. This image sums up why they made it a Decade Volcano in the 1990s; it’s still extremely dangerous today. (Image: NASA Earth Observatory)

Original post

Taal Volcano, in the Philippines, never went back to sleep. Now there has been a relatively small explosion in the small lake on Volcano Island. This news report from about eight hours ago is the source of that feature image above.)

The latest update, from PHIVOLCS’ Taal bulletins web page, is posted below this embedded tweet.

Even though I’m a layperson, those sulfur quantities seem insane. Magma must be very close to the surface again. Is stronger activity, as in January 2020, on the way?

Per my personal favorite online news source for social responses locally, last reported eight hours ago, evacuations haven’t yet been called.

Update, 4:13 p.m., Pacific: Per this CNN Philippines report, posted within the hour, some evacuations are underway. Also, PHIVOLCS reportedly does not expect a repeat of the big January 2020 blast because Taal isn’t pressurized.

Still, active volcanoes are a little like cats. You never know what will happen next.



Alert Level 3 (Magmatic Unrest) was raised over Taal Volcano at 3:37 PM today, after a phreatomagmatic eruption from the Main Crater occurred at 3:16 PM. The eruption lasted five (5) minutes based on visual monitors and generated a dark jetted plume approximately one (1) kilometer high. The event recorded mid-course as a low-frequency explosion earthquake but was not preceded by seismic or ground deformation precursors. However, anomalously high volcanic SO2 gas emission preceded the eruption, averaging 14,241 tonnes/day and 13,287 tonnes/day respectively on 28 June and 1 July (morning of today) 2021. A marked increased in volcanic gas upwelling also began on 28 June 2021 that generated plumes that rose some three (3) kilometers above Taal Volcano Island.

Since the phreatomagmatic event earlier this afternoon, four (4) short phreatomagmatic bursts have occurred that lasted not longer than two (2) minutes each and produced short jetted plumes that rose 200 meters above the Main Crater Lake. These events occurred at 6:26 PM, 7:21 PM, 7:41 PM and 8:20 PM. Upwelling of the Main Crater Lake that began at 8:07 PM tonight is ongoing.

The Alert Level 3status of Taal means that there is ongoing magmatic extrusion at the Main Crater that may further drive succeeding explosions. PHIVOLCS strongly recommends Taal Volcano Island and high-risk barangays of Bilibinwang and Banyaga, Agoncillo and Boso-boso, Gulod and eastern Bugaan East, Laurel, Batangas Province be evacuated due to the possible hazards of pyroclastic density currents and volcanic tsunami should stronger eruptions subsequently occur. The public is reminded that the entire Taal Volcano Island is a Permanent Danger Zone (PDZ), and entry into the island as well as high-risk barangays of Agoncillo and Laurel must be prohibited. All activities on Taal Lake should not be allowed at this time. Communities around the Taal Lake shores are advised to remain vigilant, take precautionary measures against possible airborne ash and vog and calmly prepare for possible evacuation should unrest intensify. Civil aviation authorities must advise pilots to avoid flying over Taal Volcano Island as airborne ash and ballistic fragments from sudden explosions and pyroclastic density currents such as base surges may pose hazards to aircraft. DOST-PHIVOLCS maintains its close monitoring of Taal Volcano and any new development will be communicated to all concerned stakeholders.


Older updates, through March 2020, here.

Taal Decade Volcano post, with update from March 2021.

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