Here’s What Scientists Are Watching If Taal Volcano Explosively Erupt

The coming days will be a tense wait to see if the eruption will intensify-threatening lives and property-or sputter out for more than 500,000 residents of the exclusion zone around the Philippines' Taal volcano, which began erupting on Sunday. Taal is capable of producing all three of the deadliest volcanic hazards: tsunamis, mudflows, and superheated flows of gas and debris if activity ramps up.

Taal is the second most active volcano in the Philippines, which is located at the confluence of several tectonic plates. The entire volcanic complex presents a lake filling the main crater, which itself is an island in a giant lake that fills the old caldera that formed after catastrophic eruptions about 500,000 and 100,000 years ago.

Michael Manga, a volcanologist at the University of California, Berkeley, said the quandary for those trying to predict Taal's next movements is that seldom unrest leads to the eruption, and sometimes it doesn't.

However, there are particular signs among the symptoms of unrest that volcanologists could watch for to shed light on what outcomes are more likely. There are seismic signs and others that geologists will be waiting for indications of what this one will do.

A link to the past

Experts can look to the past for hints to understand what that means. Ed Venzke, Smithsonian Institution's Global Volcanism Program's database manager, remarked that the most recent past eruption at Taal was a minor steam-driven event in 1977.

Amy Donovan, an expert in volcanic risk at the University of Cambridge, said Taal has "clearly been restless for a very long time while there may not have been an eruption for four decades.

Many of Taal's eruptions have been violently explosive and frequently fatal, although often moderate when compared to other volcanic eruptions, due to the vast number of people living on or close to it.

More ash production often accompanies bigger booms that would exacerbate. Water supplies become polluted, electronic infrastructure becomes damaged, agriculture becomes smothered, and farm animals and pets would be killed due to ash. People with pre-existing respiratory ailments are most at risk, as are the very young and the elderly, as breathing in glassy ash is always bad.

Aside from pyroclastic flows that killed thousands of people in mere moments, Taal also previously produced thundering, high-velocity clouds of hot ash, debris. Boris Behncke, a volcanologist at Italy's National Institute of Geophysics and Volcanology, shared photos from a 1911 eruption that killed 1,335 people on the central island.

Donovan says a reasonable worst-case scenario would show a low-altitude surge of ash and hot gas that can literally bounce over the water due to their low density.

Bartel, on the other hand, said the base surge could sandblast everything in their way, including the lakeshore on the other side.

Tsunamis that will swamp the lake's shorelines may happen if explosions dislodge parts of the volcanic island that then fall into Lake Taal. A small volcanic collapse would generate a lethal tsunami - just like Indonesia's Anak Krakatau explosion in December 2018.

Falling debris and volcanic earthquakes can cause peculiar and potentially destructive waves known as seiches, even if there is no tsunami. The debris can miss the lake entirely and instead land directly on the shore if the volcano has enough energy to explode.

Back to Taal's future

Of course, forecasting eruptions is fraught with difficulty. Nobody knows how the properties of the magma under Taal have changed since the 1977 explosion, Donovan pointed out.

The past can only tell you so much while looking at old eruptions for clues is helpful. Venzke says nothing is guaranteed as every volcanic eruption is different.

Taal might just generate a bit of ash, have a few fire fountains, then go back to sleep again, Donovan says, noting the possibility of a grime future may not transpire while seeing the worst of what Taal has to offer this time.

James Hickey, University of Exeter's geophysical volcanologist, says what Taal is exhibiting could perhaps be the opening salvo of a far more extended eruption sequence. He added some, all, or none of these hazards might occur even if the eruption becomes more explosive.

Donovan says people in the region considering the worst-case scenario is unfolding and to take reasonable, responsible action is sensible.

Since lessons from the past show just how dangerous this particular peak can be, volcanologists still have to wait with bated breath.