Eruptions Newsletter #22 for October 31, 2025

Activity News

Taal, Philippines

The unrest and explosions at Taal, near Manila in the Philippines, has been on the upswing across the last few weeks. PHIVOLCS noted that the volcano experienced 60 “seismic events” (earthquakes and tremor) on October 30, the highest across the entire month. The number of earthquakes recorded in October are much higher than in September as well. Couple that with more steam-and-ash explosions from the central vent of the volcano this week and one could be getting nervous.

That being said, PHIVOLCS doesn’t think Taal is heading directly into a new active period of eruptions. The seismicity happening at Taal are more related to the hydrothermal system (hot water moving under the volcano) than any new magma arriving at the volcano. This means the current threat is more to people who try to venture into the exclusion zones at Taal as these steam-driven explosions are hard to forecast. PHIVOLCS has the volcano at Alert Level 1 of 5.

Atka Volcanic Complex

Over the last few months, things have been pretty quiet when it comes to US volcanoes. Looking at the big picture, that is probably a good thing. Beyond the repeated eruptions at Kīlauea, unrest at Shishaldin and continued slow lava flow eruption at Great Sitkin, nothing much as been doing.

However, as October closes, we have a slight change to that list. Korovin, part of Alaska’s Atka Volcanic Complex on the remote islands of the same name, appears to have experienced an explosive eruption on October 29. With the timing at night and the volcano’s isolated location, the explosion was only “observed” by infrasound and seismic measurements. The data suggest that it was small and the Alaska Volcano Observatory didn’t think ash would spread much further than the slopes of Korovin.

This is the second such explosion at Korovin in 2025 and the first since late April. It may be a phreatic (steam-driven) explosion rather than one with much, if any, new magma. This might imply that, much like the April event, we shouldn’t expect much more to follow. Even so, AVO raised the alert status at the Atka Volcanic Complex to Yellow/Advisory.

After an 18 year hiatus, Korovin began experiencing these small explosions in March 2024. As I mentioned, Korovin isn’t really near anything. No one lives within 10 kilometres of the volcano and only 207 live within 100 kilometres — all of those in the town of Atka on Nazan Bay. You have to go back to 1998 for the last significant activity at the Atka Volcanic Complex when a series of lava flows and explosions added up to a VEI 3 event.

Whakaari (White Island), New Zealand

A small explosive eruption likely occurred on Whakaari (White Island) in New Zealand on October 30. This new activity prompted GNS Science to raise the alert status at the restless island volcano to Level 3 and the aviation alert to Orange. The eruption was noticed on the webcams pointed at the volcano, but little ash was picked up on radar.

The legal battle over the deaths and injuries from the 2019 tragedy on Whakaari continues. Earlier this year, the conviction of the tour operators was overturned, but a new inquest into the official emergency response to the blast that killed dozens has going on over the past month in New Zealand.

Volcano Word (and Research) of the Week

If you have been reading my articles about volcanoes for a while now, you’d know I love a good “lost volcanic eruption” mystery. The record of massive eruptions in the Earth’s ice cores has been a boon for understanding past climate perturbations and volcanic activity. However, there are multiple big events seen in the ice core record that don’t match with any known eruption. So, how do we figure out the culprit(s) behind these potentially global events?

One way is to look at the ash that also gets trapped in the ice core record. Because we can “read” ice core layers like calendar going back in time, any material in the ice can be linked to specific years (or so). Many times, big and/or nearby volcanic eruptions will leave discernible layers of volcanic ash and/or sulphur in the ice. The sulphur gives us information about potential climate cooling related to a big eruption.

Looking at the ash can give us information on the location and identify of the offending volcano. Although not exactly like a fingerprint, the elemental composition of volcanic ash (which is volcanic glass) will allow a volcano to be included in a list of potential sources or get rejected from that list. However, you need to have enough ash to be statistically significant (or, better said, statistically robust) and you need analyses that are reasonably accurate and precise. Both of these criteria can be tricky when you are looking at ash fall from distant eruptions — the study of what is called cryptotephra.

Cryptotephras are really just ash fragments that are very low abundance in the material you are studying. You wouldn’t even notice any ash if you weren’t looking. However, if you process the sample of deep sea sediments or ice cores, you can extract maybe a handful of ash fragments — which is enough to start to make these compositional connections. You aren’t going to be able to date the ash directly, but ideally the location in the sediment column or ice core will allow you to date the ash by correlating with other age proxies like isotopes or organic material.

There is a new study in Nature Communications: Earth & Environment by Seokhyun Ro and a host of others that uses cryptotephras from Antarctic ice cores to solve one of these eruption mysteries. Turns out that although their work confirmed the culprit of one major eruption in the 1450s, it may have created a new mystery of a second blast.

Ro and colleagues samples ash fragments from one of the Vostok ice cores. Now, I was curious just how destructive this kind of sampling might be for very challenging and expensive things to collect like deep ice cores. My colleague down the hall (Dr. Stacy Porter, former member of the Byrd Polar Research Center) said cores are slowly chipped away for different research but pain is taken to preserve as much as possible. However, there is no way around the fact that if you need to analyse volcanic ash, you have to melt the ice. Research can be costly in more than one way!

The ash fragments from the core were clearly a cryptotephra — the entire data set from this study was 14 ash fragments. They analysed the composition and size of the ash fragments and found that there were two main populations - dacite ash from Kuwae in Vanuatu and rhyolite ash from some other source.

Now, by itself, this isn’t a new finding. Previous research on ice cores elsewhere in Antarctica have found these two types of ash. That is what lead to the determination that the late 1450s sulphur peak was likely from Kuwae in Vanuatu as the dacite ash matched. However, the rhyolite ash was a surprise and suggested a second large eruption happened during the decade, likely adding to the climate impact of the Kuwae blast. The original study pointed at Reclus in southern Chile as the source of that ash.

This new research by Ro and others as able to collect more refined compositional data that seems to support the idea that Reclus may not be that mystery rhyolite ash source. The compositional data combined with a lack of any record of activity at Reclus in the 1450s suggest that some other volcano could be the source. The size of the ash fragments supports the idea that it has to be in the southern hemisphere, but candidate eruptions are scant.

I did a quick scan of eruptions in the southern hemisphere during the 1400s in the Global Volcanism Program’s Holocene eruption database and really didn’t find any really great candidates. The problems are two fold: first, the magnitude of many eruptions aren’t quantified and (2) the historical record is scant. The only verified VEI 5+ eruption during this time is Pinatubo, although Kuwae was more than likely as big or bigger. A few other volcanoes like Taranaki, Taveuni, Witori and others may have been active, but the magnitude is not constrained and their composition is right.

So, we're back to a rhyolitic eruption in the southern hemisphere during the 1450s from … somewhere? I do love the idea that even here in 2025, there are big volcanic eruptions in the past 1,000 years that we don’t even know happened. The search for the culprit (or co-conspirator) continues!

Odds & Ends

Take any press releases from a company with a massive grain of salt, but Mazama Energy in Oregon reached a potential milestone for geothermal energy near Newberry Caldera. According to Mazama Energy, they were able to reach a maximum temperature of ~330C (629F) in their geothermal wells, making them the hottest engineered geothermal system on Earth. That kind of heat could generate a lot of power, upwards of 200 MW according to the company. Whether or not the total output will be reached is to be seen.

I saw a couple headlines saying that earthquakes occurred near Axial Seamount off the coast of Oregon this week. This included a Daily Mail classic of “Major earthquakes hits just miles from underwater volcano set to erupt off US West Coast”. So, I checked and the earthquakes were M4-5 (moderate, not major) and indeed “miles” from the volcano. Of course, it was ~100 miles from the volcano, but let’s not quibble. That is not close to Axial Seamount by any stretch of the imagination. A bit like saying an earthquake in Salem, Oregon has somehow something to do with Mount St. Helens.

Of course, what might be worse is Dr. Wendy Bohon’s post on Bluesky about AI slop news articles purporting non-existent and impossible earthquakes happening including this gem:

Not only did no earthquake occurring anywhere near the area during the timeframe the article states, but magnitude 33? On the scale that goes up to M9.9? We are indeed in the stupidest of times.

Sounds of the Week

Oddly enough, when I was writing about ice cores, this song from Ultravox’s 1977 album Ha! Ha! Ha! randomly arrived on my speakers. Seems timely?

Questions? Comments? Thoughts? Feel free to leave a comment, send me a note or follow me on Bluesky (@erikklemetti.bsky.social).

Be sure to check out my podcast, 5 Minute Volcano and the Patreon page for the Eruptions Newsletter/5 Minute Volcano Podcast.