Eruptions Newsletter #20 for October 3, 2025

So, it turns out that the current US government shutdown will also shutter the Global Volcanism Program’s Weekly Volcanic Activity Report run by the Smithsonian and US Geological Survey. On top of this, any updates to the GVP will likely end October 6 if the government is still closed. Depending on how my time is spread, I may post some extra updates as news warrants here or on Bluesky.

Activity News

Kīlauea, Hawai’i

Apparently Kīlauea and I have decided that every two weeks is a good cycle to put something new out. Episode 33 of the eruptions that began at the volcano’s summit in December 2023 started in the early morning hours of October 1 and ended just after sunrise. This new eruption had some impressive lava fountaining like many of the other episodes, although this one had both an inclined and vertical component (see above and below).

It might be a product of the perspective, but the vertical fountain looked like it produced finer volcanic debris (tephra), likely in the form of basaltic ash. The inclined fountain looks to have larger volcanic bombs comparatively. I don’t know what that could be attributed to — maybe the geometry of the vent for each fountain? It is just fun to notice these subtle variations because when we reconstruct ancient eruptions, seemingly disparate features might be from the same event.

Oh yes, and note that there won’t be further pictures or updates from the Hawaii Volcano Observatory thanks to the US government shutdown as well.

Taal, Philippines

It may have been only a small eruption, but it is always important to keep a close eye on Taal in the Philippines. The fact that 24 million people live within 100 kilometres of the volcano will do that. I’ll give that some context for you: imagine everyone in Florida living within 100 km (~72 miles) from a potentially highly explosive volcano.

Taal is a caldera volcano with a large lake filling much of the depression formed ~5,500 years ago. However, it has a long history of moderate to strong eruptions. Since 1900, it has had 16 periods of activity, with two VEI 4 eruptions in that mix.

The current eruptions began in April 2024, but for the most part have been relatively small events. The eruption was two steam driven phreatic blasts according to PHIVOLCS and it hasn’t been followed by any other activity. That being said, the civil authorities in the Philippines extended a flight ban around the volcano until Friday.

Measurements of the lake water temperature in the crater on the island within the calder (yes, it is a little complicated and best) was measured at ~68.7C and slight uplift was recorded at Taal as well.

Reykjanes Peninsula, Iceland

The eruptions near Grindavík (known as the Svartsengi eruptions) in Iceland ended in early August. However, just like in Hawai’i, the Icelandic Meteorological Office has gotten good at keeping tabs on whether a new eruption is coming. By examining how much the ground is deforming as magma rises up under the area, the IMO can estimate the volume of magma that has intruded. They have found that eruptions tend to begin once that volume — and thus, the pressure in the magma body — hits a critical threshold.

The most recent estimate is that over 11 million cubic meters of magma have filled in under the area since the last eruption ended. That volume is close to the 11-13 million cubic meters that ended up erupting during the July and August activity in the Svartsengi field. All of this has the IMO thinking that we should see a new eruption “sometime before Christmas”. This is a much longer interval than what Kīlauea is doing right now, which is closer to every 2-3 weeks. However, it is the same idea in concept.

Volcano Word of the Week

This week’s word is dyke or dike (depending on which side of the Atlantic you are). A dike is a linear (actually planar, see below) feature of igneous rock or magma that cuts across older rocks. This is a term that applies to both the rock record and active magmatic processes. Yet, in both cases, it is capturing the same thing: the movement of magma.

When magma rises through the crust, it doesn’t just come up in a pre-made pipe or a giant balloon like some old textbooks would imply. Much of the time, magma will take the path of least resistance. This many cases, this would be along faults formed by the stretching of the crust caused by the buoyant magma taking up space as it rises. This “shatter and rise” movement is what gives rises to both uplift and earthquakes in areas that magma is on the move.

This means that at volcanoes like Kīlauea, you get sheets of magma rises along a plane rather than a single “tube”, especially when a new eruption site starts up. You can see this clearly in the image (above) from the 2011 eruption near Nāpau Crater on Kīlauea. It is also readily apparent in the map of the eruptions near Grindavík in Iceland (below) over the past few years. These fissure eruptions usually coalesce into a single vent with time, but they start out as a linear feature when the dike intersects the surface.

Long after the eruptions are over, these intrusions leave their mark on the rock record as what appear to be linear features (on a 2D surface) of magma “crosscutting” older rocks. Usually you can tell the age relationship by looking at the edge of what you think was the magma — it should have a finer-grained texture where it cooled fast next to the cold solid rock it passed.

The shot of a dike on the slopes of Italy’s Etna shows off the planar geometry of the dike. The loose volcanic material that surrounded it has eroded, but the solidified magma in the dike is more resistant, so you get a “fin” of basalt rock. Hike around many partially eroded basaltic volcanoes like Etna or North Sister in the Cascades and you’ll find dikes like these that once fed eruptions.

Not all dikes need to be basalt, either. The photo of a dike at Mineral King in California is a rhyolite dike related to the intrusion of a large body of rhyolite (granite) into the ancient crust of what is now the Sierra Nevada.

Dikes can vary in width from centimetres to kilometres, although sizes in the meters to tens of meters is most common. If you turn a dike on its side, so the magma is intruding into the crust as a horizontal feature, it gets called a “sill” although they are really the same type of feature.

Odds & Ends

We all like a good volcano-related TV spot, right? Anyway, it is all nonsense as the average basaltic lava flow is ~1200C/2100F. The flames on a gas stove will heat at ~200-300C/400-600F, so I question the survivability of the pan depending on its quality. Also, the plucky dishwashing scientist (?) would not look so comfortable placing the pan on the lava flow — when I’ve sampled lava flows, the heat is unbearable without protective gear.

I’m sure the only “real” volcano footage is the setting shot at the very beginning … which I think is from Iceland? The rest is CG and hopefully not AI CG, but it is hard to tell.

The flame thrower to add insult to injury is a nice touch, but I would say that a dishwasher is definitely not typical field equipment, but the dirt on the sides of the dishwasher is a nice touch. And I likely wouldn’t put a water tower (below) so close to the eruption unless you really want to add some pop to the activity.

Sounds of the Week

How about some Volcano Suns? They were the side project of the former drummer of the seminal Boston alt rock band, Mission of Burma.

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.