Eruptions Newsletter #8 for May 2, 2025

Activity News

Let’s talk Axial Seamount!

Lot of news in the last day about Axial Seamount, a volcano located ~480 kilometers off the coast of Oregon. Axial is unique in that it is a seamount on mid-ocean ridge spreading center, a place where volcano-like edifices rarely form. It is also unique in that it will wired with all sorts of instrumentation even though it is ~1,400 meters (4,600 feet) beneath the ocean’s surface.

All this instrumentation means that unlike 99.9% of all other volcanism on the vast mid-ocean ridge system that spans tens of thousands of kilometers, volcanologists can monitor it for potential unrest and eruption. Folks monitoring Axial Seamount at University of Washington have suggested that the current state of unrest (deformation from magma rising and earthquakes) at the volcano means it is likely headed towards its first eruption since 2015.

Now, Axial may be on a mid-ocean ridge, it is actually a hotspot volcano like those in Hawai’i. Actually, a more apt comparison might be Iceland, where a hotspot and another mid-ocean ridge (this time in the Atlantic) coincide. However, unlike Iceland or Hawai’i, Axial Seamount has never breached the surface of the Pacific Ocean.

I’ve seen some coverage of the unrest at Axial Seamount that attempts to compare what might happen with the massive Hunga Tonga eruption in 2022. That blast was also from a submarine volcano in the Pacific Ocean and it triggered a Pacific-wide tsunami. However, the two volcanoes couldn’t be more different.

Hunga Tonga erupts much stickier lava prone to explosive eruptions compared to Axial Seamount. Axial Seamount erupts basaltic lava that tends to not generate explosive eruptions. Just look at Hawai’i or Iceland today for a comparison.

Hunga Tonga is also much closer to the sea’s surface, usually with some parts above it. Seawater mixing with erupting magma can make it more explosive if the eruption is happening is relatively shallow water — maybe tens of meters deep. However, get much deeper and the pressure from the water will suppress any potential explosivity. At ~1,400 meters depth, Axial Seamount is under a lot of pressure from seawater, so explosive activity is very unlikely.

This means that what we might expect from an Axial Seamount eruption is lots of pillow lavas and maybe some sheet lava flows — all of which would require a submersible to see any of it happen in real time. Maybe we’ll get lucky and can have an ROV or the like down there when Axial does erupt, but if not, the instruments on the volcano should let us know if starts erupting anew.

Satellite images

I also threw together a few satellite images of current activity around the planet for your enjoyment.

Home Reef, Tonga

Speaking of (mostly) submarine volcanoes, Home Reef in Tonga has been erupting over the last few weeks. The explosions have been relatively small with ash and other volcanic debris being ejected a few hundred meters (few thousand feet) up. This animate GIF of two images taken by Sentinel-2 from April 23 show some wispy ash in the true color image and the red thermal (infrared signature of lava at the surface. I zoomed in on the few red pixels in the image below as well.

Bezymianny, Russia

Over in Kamchatka, Bezymianny has been producing ash-rich plumes of the past week as well. You can see the grey ash at the summit clearly on top of the white snow. A steam-and-ash plume is lazily drifting off to the west as well in this April 28 Sentinel-2 image.

Etna, Italy

This thermal (IR) image of the summit of Etna is impressive by the shear number of hotspots. A few come from the summit crater vents (middle of the image), with the one of the brightest being the Nord-Est (northeast) crater, followed by Bucco Nuovo to its lower left. The bright area to the lower right of the summit is the Nuovo Cratere di Sud-Est (new Southeast Crater) and it shows not only the crater but some new lava flows stretching down the slopes to the south and east as well. (By the way, the image is blurry because the shortwave IR camera has a lower resolution than the true color camera).

Poás, Costa Rica

One last Sentinel-2 image for the week, this time from Poás in Costa Rica. It has been sending ash ~1 km (thousands of feet) up and sulfur emissions have increased, all hints that a more active period is likely in the works for the volcano. New ash deposits are clear on the upper slopes of the volcano and this image, taken April 29 shows thin, wispy ash streamers drifting to the southeast over the town of Poasito.

Volcano Research

So, no volcano is a zombie. That’s one of those sentences I didn’t think I’d need to write, but here we are. A flurry of news articles popped up this week about Uturuncu, a volcano in the Andes of Bolivia that has been a bit of a mystery. According satellite radar measurements, the ground surface at the volcano has been inflating and seismic monitoring shows some earthquakes as well. Both those signs might suggest an eruption is in the work.

The thing is, Uturuncu has been dormant for possibly hundreds of thousands of years. Now, a dormant volcano is not a dead volcano and there are no cut and dry guidelines about how long it takes for a volcano to become “dormant” versus “extinct” (that is “dead” in volcano-speak). So, the long period of time since the last known eruption is definitely long, but many volcanoes share this trait.

The research by Ying Liu and others in PNAS suggest that much of the unrest at Uturuncu is related to hydrothermal systems active above the large magma body known as the Altiplano-Puno Magmatic Body (APMB). Superheated brines, steam and fluid-filled cracks are the drivers for the inflation and seismicity rather than magma rising up into Uturuncu. Hydrothermal systems are well known as drivers of such activity — Yellowstone is a great example — so this research shows that this is also happening at smaller volcanoes.

Sounds of the Week

No direct tie to the themes from this week (beyond the title, which is about as loosely as you can connect to a newsletter on volcanoes), but one heck of a banger from this upstart Nova Scotia band. Enjoy the rock and roll.

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