Taal Caldera (July 11th status update)

I learned so much new stuff about this Decade Volcano while revising the eBook that I wanted to share the chapter. A factor in that decision is Taal’s current unrest — I’ll pin the “Taal unrest” post whenever its status changes. This post/chapter tells you why that matters. (Also, I corrected the VAAC and added some media.)

There are many active volcanoes in the Philippines. Only one of these comes to mind when we think of that country during the Nineties: Pinatubo, about 60 miles north of Manila, the nation’s capital.

But this is not the volcano we’re looking at today.

Mount Pinatubo’s June 1991 eruption was catastrophic, and its effects on Filipinos are still felt.

However, there is an even more dangerous volcano sitting only 44 miles south of Metro Manila.

It slumbered restlessly during the 1990s, but the Decade Volcano selection people couldn’t ignore it, although the rest of the world did — until its lightning-charged eruption on January 12, 2020.

That volcano is Taal Caldera.

And what we saw in 2020 was not the worst that Taal can do.

Where is this?

It’s in Batangas Province, located on the southwestern tip of Luzon Island.

Those are just words to many of us outside the Philippines.

Quite frankly, it is only while researching this revised edition of the Decade Volcano book that I’ve learned just how gorgeous Taal Lake and the tropical province of Batangas really are.

Urbanites weary of Manila’s crowds, noise, and traffic know all about it. Batangas Province, Taal, and Taal Lake are among the biggest tourist draws near the capital. (Delos Reyes)

This region is also a good place to live.

Fish farmers raise tilapia in Taal Lake’s fresh water while herdsmen manage livestock and poultry onshore and also on Taal Volcano Island out there in the middle of the lake (thousands of people live on Volcano Island — the focus of all historically recorded eruptions — despite long-term residence being banned in that officially designated Permanent Danger Zone).

Optimism and a belief that “it’ll happen to somebody else” come easily when you’re in your twenties (per Delos Reyes, the median age in Batangas is 24).

This youthful province is also an economic powerhouse.

Besides aquaculture, husbandry, and tourism, Batangas residents do quite well for themselves in such fields as forestry, cottage industries, services, and manufacturing.

Batangas also hosts the Philippines’ second largest international seaport. (Delos Reyes)

It’s quite a bustling place.


Based on its complex and little-understood eruptive history and its enormous potential for disaster, Taal was chosen as a Decade Volcano by the Philippine Institute of Volcanology and Seismology (PHIVOLCS) from among 200 potentially active volcanoes in the Philippines. Taal is frequently active, several million people live within a 20-km radius of its caldera rim, and it is surrounded by well-utilized infrastructure. Although its hazards were momentarily eclipsed by events since 1991 at Mount Pinatubo, Taal is the larger threat to the Philippine population.

— Torres et al., 1995

That’s serious talk, and to show how well scientists and hazard managers have since walked it, consider this (Bato et al.; Lagmay et al.; Rappler):

  • Taal’s 2020 blast, rated VEI 4 by the GVP, affected over half a million Filipinos and caused $69 million in damage — but “only” 39 people died in it.
  • Thirty-eight of those fatalities were from indirect causes like traffic accidents and stress reactions.
  • The 2020 eruption directly killed just 1 person, who didn’t leave Volcano Island when an evacuation was called. It probably also got another individual who had stayed behind and was still missing at last report from Bato et al.

In contrast, an estimated 1,335 people died during a comparable eruption of Taal in 1911. (Bato et al.; Brown et al.) Of note, fewer people lived near Taal back then.

Now, the difference in casualties isn’t totally due to improved volcano monitoring and hazard management from the early 1990s on.

Those advances have helped a lot, but it’s also true that in 2020 Taal didn’t use its full arsenal of death-dealing effects, as it did in 1911 and in 1965 (when hundreds perished in yet another VEI 4 eruption).

What might those lethal weapons be?

Earth, wind, fire, and water, basically — all of them powered by a magma reservoir that may be sitting 3 miles or so underneath or near Volcano Island. (Bato et al.; Yamaya et al.; Zlotnicki et al.)

Hazards at Taal

Earth is rock, and volcanic ash is powdered rock. The person who died on Volcano Island in January 2020 was found under 5 feet of the stuff. (Lagmay et al.)

Fiery, turbulent wind is what carried all that material in a pyroclastic flow, burning and blowing down the hapless human being. It travels much faster than anyone can run.

Luckily for the Philippines, at least six millennia have passed since enormous pyroclastic flows from Taal’s last caldera-forming eruption resurfaced Batangas, Cavite, and Laguna provinces (total population in 2020: 10,635,515, per PhilAtlas.com). (Delos Reyes)

This video of the top ten sites in Cavite is in Tagalog, but pictures are worth a thousand words. The waterfalls, I think, are flowing over Taal’s pyroclastic flow deposits.

The magnitude of such an event takes a while to sink in. And this was only the most recent of several ash-flow eruptions — not supersized, as far as anyone knows, but really big — at Taal in the distant past! (Delos Reyes)

Moving on, there is one more hazard to cover:

Water plays multiple roles, as you might expect given the lake and this volcano’s location on a rainy tropical island, sitting very close to the coast (per Hargrove and Medina, Taal used to be open to the sea, as Rabaul Caldera, in Papua New Guinea, is today).

Usually benign H2O has two killer effects here:

Sandblasted trees from the 1965 eruption. (Image: USGS/J. G. Moore via Oregon State’s VolcanoWorld)

  1. Base surges: These are heavy, wet pyroclastic flows that whoosh along like a sandblaster’s mud at almost 70 mph, smashing everything in their path. In 1965, their sharp-edged ash particles scoured off 6 inches of trunk on large trees, 700 feet away from Taal’s vent. (Lagmay et al.; Moore et al.)

    Lagmay et al. report that in 2020 base surges killed more than a thousand livestock on Volcano Island and travelled more than a third of a mile across the water.

    In 1911 and 1965, pyroclastic flows and/or base surges rolled over the lake and devastated shore communities west of Volcano Island. Sandblasting effects in 1965 were noted up to 5 miles away from the vent. (Delos Reyes; Global Volcanism Program)

  2. Tsunami: Yes, big waves in lakes are usually called a “seiche.” This is caused by the wind or some other phenomenon that builds a standing wave — vertical water movement.

    As I understand it, lakes with explosive volcanoes in them can also have tsunami — horizontal movement of the water — caused by explosions, the impact of pyroclastic flows, or even landslides. (Paris and Ulvrova)

    Since Volcano Island and its 40-some vents aren’t very far from the heavily built-up shore, it’s fortunate that no big waves formed during the 2020 eruption of Taal.

    In that case, high-risk zones had been evacuated, but the material damage might have been much worse.

    Paris and Ulvrova note that everything from schools and coastal resorts to fish farms and even the Taal Volcano Observatory are vulnerable to tsunami, which would speed through the lake in minutes and, on arrival, could be over 30 feet high in a worst-case scenario.

    Most of the casualties in 1911 were from tsunami (Moore et al.), which also wiped out several communities near the shore. (Delos Reyes)

    Tsunami during the 1965 eruption claimed over 250 lives and destroyed villages west of Volcano Island. (Brown et al.; Delos Reyes)

I totally sympathize with your impulse right now to crawl under something and hide until they clear everyone away from Taal Caldera forever.

This is why I put the reasons that draw Filipinos to Taal’s region first, before the hazards, so you might understand: nobody is going to abandon this rich and scenic place, despite the dangerous neighborhood volcano — especially if their family connections to Batangas run deep.

Anyway, where would they all go?

That’s a practical question over the long term, too.

Taal hasn’t had any of its caldera-forming eruptions in a very long time, in human reckoning. That’s probably why worst-case modeling for hazard maps is based on data from the devastating 1754 VEI 4 blast.

It makes sense. More extreme eruptions don’t happen very often. Tens to hundreds of thousands of years can pass in between caldera-forming blasts. (Oppenheimer)

That’s reassuring, but let’s not forget that volcanoes don’t always follow the rules.

What if a repeat of the ca. 3600 BC province-resurfacing VEI 6 eruption — two orders of magnitude more intense than the worst-case model — was on the way and they did need to evacuate Batangas, Cavite, and Laguna provinces, perhaps quickly?

How could they do it?

And even if they could, where would those 11 million refugees go? And what about Manila, and airports, seaports, highways, healthcare, food supply lines…?

Don’t worry. There’s absolutely no sign that anything as riproaring as that is coming up at Taal.

As far as they know.

As Delos Reyes wrote in 2019, the possibility can’t be ruled out based on current knowledge.

Now you have some idea of why PHIVOLCS in the 1990s, even though they were dealing with a vicious Mount Pinatubo at the time, selected Taal as their Decade Volcano.

Then, as now, it was imperative that scientists learn everything they could about Taal Caldera as quickly as possible.

What did the Decade Volcano program accomplish?

Through the Decade Volcano program, experts realized “the remarkable extent in which water is involved in eruptions of Taal Volcano.” (Newhall)


Yes. And they weren’t just talking about base surges and tsunami, either. (Or about its potential contribution to volcanic lightning.)

While most of us think of volcanoes as earth, wind, and fire, geoscientists know that water is a major player in any eruption

The reasons why aren’t obvious, and the physical and chemical details are tricky.

Let’s just say that, deep underground, the amount of water locked into hydrous minerals, or dissolved into the melt under high pressure, and/or trickling through cracks and crevices as a magmatic fluid of some sort can affect, among other things, the chemical composition of magma and (along with many other factors) the likelihood of an eruption, plus how explosive that eruption might be.

At or near the surface, of course, it’s much simpler: water meets magma, and BOOM!

There’s a steam explosion or even a phreatomagmatic eruption, producing very fine ash particles that can travel a long way, affecting a wider area than a “drier” eruption would. (Newhall; Van Eaton et al.)

Mount Pinatubo, before its big blast, was not a lake volcano. (Image: Chris Newhall via Wikimedia, public domain.)

For example, the Global Volcanism Program lists Mount Pinatubo’s June 1991 eruption as VEI 6.

Bad as that was, it didn’t bury three provinces under pyroclastic flows.

Taal’s VEI 6 rampage, back around 3600 BC, did: Batangas, Cavite, and Laguna provinces. (Delos Reyes)

And these ancient eruptions might have happened through a body of water. (Ramos)

The presence of water affects eruption columns in many ways. (Van Eaton et al.)

Caldera-forming phreatoplinian or subplinian eruptions at Taal through a lake or shallow sea inlet — whatever existed there thousands of years ago — could pulverize erupting material so finely that it would spread over an unusually broad area while soaring in roiling, fiery clouds — up to the stratosphere in extreme cases (Van Eaton et al.) — and speeding outward from the vent above ground-hugging pyroclastic density currents.

Deposits from such co-ignimbrite clouds exist in the rocky record of Taal’s ancient VEI 6 eruptions (as well as in much smaller deposits from 1754’s VEI 4 catastrophe); however, it’s challenging to map them out clearly enough to understand exactly what happened. (Delos Reyes)

Perhaps back then, as now, Taal was one of the wettest volcanoes around.

Today, it is loaded with water from:

  • Taal Lake and a small volcanic lake that accumulates inside the island’s Main Crater in between eruptions.
  • Groundwater from 30 inches of rainfall yearly. (Weather Atlas)
  • Whatever salt water still manages to seep through the old connections with Balayan Bay that made Taal an inlet until eruptive deposits in 1754 walled it off.

No wonder that most of this Decade Volcano’s recorded eruptions have been hydrovolcanic! (Delos Reyes)

Where is that water stored? In the lake?

No, underground in a hydrothermal system — you know, geysers, hot springs, steam vents and the like.

It isn’t the size of Yellowstone’s, but a 2013 study by Yamaya et al. suggests that Taal’s hydrothermal system is big.

The researchers also note that this hydrothermal system, in addition to local tectonics, might control Taal’s eruptions!

Here’s their model of how that could happen:

  • About 1-2 miles below the caldera’s surface, circulating through faults and other openings in the rock down there, lake water, groundwater, and seawater, as well as magmatic fluids and gases, form a hydrothermal field. It shows itself at the surface in fumaroles, mud pots, steamy upwelling and occasional geysering in Main Crater’s lake, etc.
  • This hydrothermal system sits above a reservoir of magma about 3 miles down that is periodically replenished from below because Taal is a subduction zone volcano. Just offshore to the west, the South China seafloor plate is grinding down and eastward under Luzon at the Manila Trench. (Delos Reyes; Ku et al.)
  • While the system is stable over geologic time, chemical reactions between Taal’s briny, acidic hydrothermal fluid and the surrounding rock alter some of that rock into clay. Underground pressure and other forces then smoosh this clay together at the top of the circulation system, where it hardens into a cap.

    Judging by signs on the surface, Yamaya et al. suspect that currently this caprock is thinnest and weakest underneath the northern part of Main Crater and Volcano Island’s north flank.

  • Taal just sits there, simmering and sputtering like an overfilled tea kettle at the volcanologists trying to monitor it and to keep everyone safe, until something disturbs the hydrothermal system — an earthquake, maybe, or an inrush of new magma from the depths.

    The caprock under Volcano Island then breaks and the pressurized system below explodes.

    Magma might or not reach the surface after that initial hydrovolcanic blast.

    Historically, Taal has had a variety of lava eruptions — anything from flows on Volcano Island to Strombolian fireworks to lava fountaining (which occurred in 2020 on a small scale). (Delos Reyes; Lagmay; Rappler)

    Again, Tagalog, but there some nice shots of the 2020 fountains at night at around 0:45 that you might not have seen yet.

    As dramatic as they are, such explosive events aren’t always major eruptions (though 2020’s certainly was!)

    Of Taal’s 37 eruptions on the Global Volcanism Program list since 1572, only five have been as powerful as VEI 4.

    The others are in the 2-3 range, with even some VEI 1s in there.

It’s only a model, and quite oversimplified, but at least it hangs together.

Very probably other ideas, more detailed and possibly more accurate, will come in the future as work continues that was given such a boost through the Decade Volcano program.

In the meantime, let’s hope that, after waking up in 2020 so violently, Taal eventually settles down into a long and peaceful sleep.



14.002° N, 120.993° E, in Batangas Province on southwestern Luzon, the Philippines. The GVP Volcano Number is 273070.

Nearby Population:

Per the Global Volcanism Program website:

  • Within 5 km (3 miles): 717,090.
  • Within 10 km (6 miles): 717,090.
  • Within 30 km (19 miles): 2,380,326.
  • Within 100 km (62 miles): 24,814,047.

Those are official numbers. In addition, an estimated 5,000 people lived on Volcano Island in 2016, even though the island is designated as a Permanent Danger Zone, for obvious reasons, and has no services. (Delos Reyes)

Current Status:

On July 11, 2022, PHIVOLCS lowered the level to Level 1.

This is part of PHIVOLCS’ June 26th bulletin (today’s):

In the past 24-hour period, the Taal Volcano Network did not detect any volcanic earthquake, but a low-level background tremor has persisted since 13 June 2022.

Activity at the Main Crater was dominated by the generation of plumes, 600 meters tall plumes drifting southwest.

Sulfur dioxide (SO2) emission averaged 2,840 tonnes/day on 23 June 2022.

Temperature highs of 66.5°C were last measured from the Main Crater Lake on 27 April 2022.

Based on ground deformation parameters from electronic tilt, continuous GPS, and InSAR monitoring, Taal Volcano Island and the Taal region has begun deflating in October 2021.

Alert Level 2 (Decreased Unrest) prevails over Taal Volcano. DOST-PHIVOLCS reminds the public that at Alert Level 2, sudden steam-driven or phreatic explosions, volcanic earthquakes, ashfall, and lethal accumulations or bursts of volcanic gas can occur and threaten areas within TVI and along its coast. Entry into TVI, Taal’s Permanent Danger Zone, must therefore be strictly prohibited. Local government units are advised to continually strengthen preparedness, contingency, and communication measures, especially for previously evacuated high-risk barangays in case of renewed unrest. Civil aviation authorities must advise pilots to avoid flying close to the volcano as airborne ash and ballistic fragments from sudden explosions and wind-remobilized ash may pose hazards to aircraft.

DOST-PHIVOLCS is closely monitoring Taal Volcano’s activity and any new significant development will be immediately communicated to all stakeholders.

Biggest recorded event:

Per Delos Reyes, in 1754 the main crater on Volcano Island unexpectedly erupted in mid-May and kept at it until early December.

Residents of Manila had to use artificial light during the day, while Taal’s 1754 eruption column may have been as high as 25 miles at times.

Pyroclastic flows and base surges laid down thick deposits and caused huge waves that washed away whatever lakeside towns weren’t already buried underneath ash.

This is the “worst-case” event that today’s emergency managers base their plans on.


The Philippines Institute of Volcanology and Seismology (PHIVOLCS). Here is their Taal bulletin page.

Tokyo Volcanic Ash Center (VAAC) issues advisories to aircraft when needed. None are in effect at Taal right now.

Featured image: etrhamjr via Wikimedia, CC BY-SA 4.0.


Bato, M. G.; Lundgren, P.; Pinel, V.; Solidum Jr, R.; and others. 2021. The 2020 eruption and large lateral dike emplacement at Taal volcano, Philippines: Insights from satellite radar data. Geophysical Research Letters, 48(7): e2021GL092803.

Brown, S.K.; Jenkins, S.F.; Sparks, R.S.J.; Odbert, H.; and Auker, M. R. 2017. Volcanic fatalities database: analysis of volcanic threat with distance and victim classification. Journal of Applied Volcanology, 6: 15.

Delos Reyes, P. J. 2019. An interdisciplinary study of the hazards associated with an AD1754 style eruption of Taal Volcano, Philippines. University of Sydney, doctoral thesis.

Global Volcanism Program. 2020. Taal. https://volcano.si.edu/volcano.cfm?vn=273070 Last accessed March 19, 2020.

Hargrove, T. R., and Medina, I. 1988. Sunken ruins in Lake Taal: an investigation of a legend. Philippine Studies, 330-351.

Ku, Y. P.; Chen, C. H.; Song, S. R.; Iizuka, Y.; and Shen, J. J. S. 2009. A 2 Ma record of explosive volcanism in southwestern Luzon: Implications for the timing of subducted slab steepening. Geochemistry, Geophysics, Geosystems, 10(6).

Lagmay, A. M. F. 2021. Taal volcano eruption: The importance of science and science communication. National Academy of Science and Technology, Philippines (NAST PHL) Science Advisory 2021-01. ___

Lagmay, A. M. F.; Balangue-Tarriela, M. I. R.; Aurelio, M.; Ybanez, R.; and others. 2021. Hazardous base surges of Taal’s 2020 eruption. Scientific Reports, 11(1): 1-11.

Moore, J. G.; Nakamura, K.; and Alcaraz, A. 1966. The 1965 Eruption of Taal Volcano: Catastrophic explosions are caused by lake water entering a volcanic conduit. Science, 151(3713): 955-960.

Newhall, C. 1996. IAVCEI/International Council of Scientific Union’s Decade Volcano projects: Reducing volcanic disaster. status report. US Geological Survey, Washington, DC. Retrieved from https://web.archive.org/web/20041115133227/http://www.iavcei.org/decade.htm

Oppenheimer, C. 2011. Eruptions That Shook the World. Cambridge: Cambridge University Press. Retrieved from https://play.google.com/store/books/details?id=qW1UNwhuhnUC

Oregon State University: Volcano World. 2020. Taal. http://volcano.oregonstate.edu/taal Last accessed March 19, 2020.

Paris, R., and Ulvrova, M. 2019. Tsunamis generated by subaqueous volcanic explosions in Taal Caldera Lake, Philippines. Bulletin of Volcanology, 81(3): 1-14.

Ramos, E. G. 2002. Origin and geologic features of Taal Lake, Philippines. Aquatic Ecosystem Health & Management, 5(2): 155-162. (Abstract only)

Rappler.com. January 26, 2020. TIMELINE: Taal Volcano’s January 2020 eruption. https://r3.rappler.com/newsbreak/iq/249503-timeline-taal-volcano-eruption-2020

Torres, R. C.; Self, S.; and Punongbayan, R. S. 1995. Attention focuses on Taal: Decade volcano of the Philippines. Eos, Transactions American Geophysical Union, 76(24): 241-247. (Abstract only.)

Van Eaton, A. R.; Herzog, M.; Wilson, C. J. N.; and McGregor, J. 2012. Ascent dynamics of large phreatomagmatic eruption clouds: the role of microphysics. Journal of Geophysical Research: Solid Earth, 117(B3).

Weather Atlas. 2022. Climate and monthly weather forecast, Batangas, Philippines. https://www.weather-atlas.com/en/philippines/batangas-climate Last accessed June 23, 2022.

Yamaya, Y.; Alanis, P. K. B.; Takeuchi, A.; Cordon, J. M.; and others. 2013. A large hydrothermal reservoir beneath Taal Volcano (Philippines) revealed by magnetotelluric resistivity survey: 2D resistivity modeling. Bulletin of volcanology, 75(7): 1-13.

Zlotnicki, J.; Sasai, Y.; Johnston, M. J. S.; Fauquet, F.; and others. 2018. The 2010 seismovolcanic crisis at Taal volcano (Philippines). Earth, Planets and Space, 70(1): 1-23.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.