Eruptions Newsletter #13 for June 6, 2025

In case you missed it, my new podcast 5 Minute Volcano debuted earlier this week. In it, you’ll get 5 minutes about a random volcano each week … this week’s choice was Lewotolok in Indonesia. Check it out!

I also debuted a Patreon for Eruptions Newsletter and 5 Minute Volcano. I’m not requiring subscriptions to access weekly content, but you can check out some potential support levels (conveniently referred to as “VEI”) to help cover the costs of hosting the podcast and newsletter (and maybe get me some coffee). Be sure to check out the bonuses at each VEI!

Activity News

Etna, Italy

Likely the biggest volcano news this week was the dramatic eruption of Etna on Sicily on June 2. The Italian volcano produced an ash plume that reached 6,500 meters (~21,000 feet). However, what caught everyone’s attention were the pyroclastic flows caused by collapse of the northeast flank of the Southeast Crater - a rare event at Etna. There was some dramatic video showing people running for cover as the pyroclastic flow raced down the volcano (see below). Luckily no one was hurt.

Here is another view of the tourist fleeing the scene.

visit__sicily

609K followers

View more on Instagram

With the amount of tourists and people around the volcano and the clear conditions, it was likely one of the most scene pyroclastic flows … well, ever, according to Dr. Boris Behncke who works at the INGV Etna Observatory.

Although many of Etna’s eruptions are relatively small explosive eruptions and/or lava flows, it does occasionally let off a significant bang. This blast was impressive, albeit brief. As Dr. Behncke mentioned in the above Bluesky post (skeet?), this is the explosive blast (paroxysm) from the Southeast Crater in a year and a half. The eruption also generated three lava flows that headed mainly down the south and east sides of the volcano after the explosion transitioned to a lava fountain (…sound familiar?)

There were some great satellite images captured of the eruption in progress by ESA’s Sentinel-2 Earth observing satellite. I’ve created a couple before-and-during pairs using the infrared (IR) images from May 31 and June 2.

I zoomed in on the summit area to really show the extent of pyroclastic flow deposits on the north east side of the volcano as well as the multiple lava flows. Covers over 6 square kilometers in the right hand image below.

This false color image (below) from Sentinel-2 shows those pyroclastic flow deposits (the lighter colored ash deposits) on the slopes of the volcano. (Remember, red in an image like this is likely plants.)

Again, zooming into the summit area and you can really see the lava flows from this eruption in the false color image.

Etna quickly returned to a much quieter state within a few hours of the June 2 eruption according to a statement from the INGV.

Kīlauea, Hawai’i

It took a smidge longer than other times, but a new episode (the 24th so far) of lava fountaining and flows began at Kīlauea’s summit during the evening of June 4 and ended by early morning June 5. As usual, the results were spectacular, especially in the night view of the summit livestream. You can really see the braided lava flows coming from the vent that is vigorously spraying basaltic lava. The starting phase of this episode created lava fountains that were ~300 meters (~980 feet) tall with a plume of gas and ash that reached 5 kilometers (~16,500 feet).

Volcano Word of the Week

Our Word of the Week is silica. You might notice that when volcanologists talk about the different types of magma, we tend to refer to “high silica” or “low silica” magma. Anyone with a background in the elements might think “hey, it is silicon, right?” Right! Except…

Silica refers to silicon oxide, or SiO₂. When geologists discuss the composition of rocks, we use the oxides of elements, so the element bonded with oxygen. Aluminum (Al) is Al₂O₃, titanium (Ti) is TiO₂ and so on.

You might wonder why would we ever use this as a convention? It comes down to how the first chemical compositions of rocks were performed in the 19th century. Instead of the fancy analytical techniques like electron beams and mass spectrometers, they used wet chemistry to determine how much of each element was in a rock.

They would need to dissolve the rock and then precipitate out each element as an oxide. Then they would weigh each oxide to get the rock’s composition. This also explains why geologists not only use oxides but “weight percentage” (commonly abbreviated wt%) oxide.

On Earth, nearly half to three-quarters of the common magma compositions are silica. That’s because silicon (the element) is the second most common element in the Earth’s mantle and crust after oxygen.

When magma is molten, it is made of free elements and chains of silica that may have some elements bonded to it as well. This is a kind of polymer where chains of silicon and oxygen form from silica tetrahedron (1 Si and 4 oxygen atoms, see above) share oxygen atoms. The more silica, the more chains, the stickier (more viscous) the magma.

So, low silica magma like basalt that might have “only” 47-52 wt% silica are runnier than high silica magma like rhyolite that has >72 wt% silica. Lower silica magma also tend to erupt at higher temperatures, ~1200°C compared to ~800°C for high silica magma, which enhances the high viscosity of rhyolite.

The most common rock forming minerals on Earth are silicate minerals full of silicon — things like quartz, plagioclase feldspar, olivine, pyroxene and more. Even when we talk about the composition of these minerals, we refer to the weight percent silica. Only elements and isotopes that are very low (<0.1 wt%) concentration in rocks and minerals get shown as elemental abundance like parts per million or billion (ppm, ppb).

We can thank the early geochemists for the odd convention we use in volcanology to discuss the composition of magma.

Odds & Ends

Not a lot caught my attention for odds & ends this week. Next week! More! Really!

Sounds of the Week

With Etna’s conspicuous activity this week, why not feature some songs about Italian volcanoes. Crazy that there are enough to feature, right?

Why not start with a song named after Etna itself. Lots of oddball charm in this one.

Not directly a volcano song, but it does talk a lot about Stromboli and has some, well, interesting comparisons Woody Guthrie makes about him and volcanoes.

As the next few songs attest, there are multiple songs about the 79 CE eruption of Vesuvius, including this banger by Siouxsie & the Banshees.

This track does a great job capturing the sense of dread lots of people feel about a potential Phlegraean Field (Campi Flegrei) eruption.

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