How and Why Etna is Unusual

A correspondent sent me THIS LINK. It is based on THIS ACADEMIC PAPER. Both links are quite complex and the best summary of them can be provided by Chat GPT.

The GA will visit Etna this June and I will be there! I look forward to hearing what degree of complexity we hear when we are on the slopes!

Here is ChatGPT's summary.

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The article explains how scientists may finally understand the unusual behaviour of Mount Etna, one of the world’s most active and puzzling volcanoes. Although Etna is over 500,000 years old and sits above a subduction zone where tectonic plates collide, its eruptions don’t match typical volcanic models. Instead of producing the kinds of magma expected in such settings, Etna frequently emits alkaline lava more typical of hotspot volcanoes like those in Hawaii—despite no hotspot being present nearby.

To solve this mystery, researchers analysed the chemistry of Etna’s lava over hundreds of thousands of years. They found that its composition has remained remarkably consistent, even as surrounding tectonic conditions changed. This suggests the magma feeding Etna is not newly formed each time, as in most volcanoes, but instead comes from a long-lasting, stable source deep underground.

The study proposes that Etna is fed by pockets of magma trapped about 80 kilometres beneath the Earth’s surface, in a region between the upper mantle and tectonic plates. As the African Plate moves beneath the Eurasian Plate, pressure squeezes this stored magma upward through cracks in the crust, much like water from a sponge.

This mechanism resembles that of so-called “petit-spot” volcanoes—small volcanic features usually found on the ocean floor. However, Etna is vastly larger, making it an unusual and possibly unique example of this process operating on a massive scale.

These findings reshape scientists’ understanding of how volcanoes can form and function, suggesting Etna may not fit into standard categories. The research also has practical importance, helping improve assessments of volcanic hazards in nearby populated areas such as Catania and Messina.

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 The Hunga-Tonga Eruption Hid its Effect

A correspondent sent me THIS LINK. It concerns the 1922 eruption of Hunga-Tonga. This occurred under water and this had the effect of disguising its impact. 

The release of sulphur dioxide (SO₂) is often used to measure the cooling affect of eruptions, but Hunga-Tonga released little SO₂ to the atmosphere. And therefore it was assumed that it had little affect on the climate. The SO₂ released reacted with sea water - I assume sulphuric acid will be somewhere in the reactants.

But the lack of SO₂ in the atmosphere does not mean that the eruption had little climactic affect. 3 billion tons of water vapour went into the atmosphere in 1 hour! And it went very high - into the stratosphere and mesosphere. And there it had complex climatic results.

Read the article to understand some of the complexities!

 Another Huge Eruption Sometime (Geologically) Soon

A correspondent has sent me THIS LINK concerning a volcano which produced the largest eruption of the Holocene. Recent research indicates that the magma chamber is slowly refilling.

When one considers the damage the Holocene eruption did to what was then a sparsely populated area - just south of Japan's southernmost large island, Kyushu - another similarly sized eruption today would be catastrophic. Population densities are rather higher nowadays!

The researchers have found that the magma refilling the magma chamber is new stuff - not the leftovers of the last eruption.

You can get a better idea of the article by reading a summary provided by ChatGPT.

The article describes new research into the Kikai Caldera, a largely submerged volcano Japan responsible for one of the most powerful eruptions in Earth’s recent geological history. Around 7,300 years ago, the volcano produced the Akahoya eruption—the largest known eruption of the Holocene—ejecting vast quantities of material, spreading ash across Japan and beyond, and likely devastating the ancient Jōmon population.

Although the volcano has remained relatively quiet since then, scientists have now discovered that its  magma chamber is slowly refilling. Using advanced seismic techniques, including air-gun pulses and ocean-bottom seismometers, researchers mapped the subsurface structure beneath the caldera. Their results reveal a large magma reservoir that appears to be the same system responsible for the ancient eruption. 

Importantly, the magma currently accumulating is not simply leftover material from the previous eruption. Chemical analysis shows it is newly injected magma, indicating an active replenishment process. This is supported by evidence of a lava dome forming within the caldera over the past several thousand years, suggesting continuous magmatic activity.

The findings provide insight into how giant caldera systems “recharge” over long timescales. Researchers propose a model in which fresh magma is gradually injected into shallow reservoirs, eventually rebuilding the conditions necessary for another large eruption. This mechanism may apply not only to Kikai but also to other major volcanic systems such as Yellowstone and Toba.

While there is no indication of an imminent eruption, the study highlights the importance of monitoring such systems. Given today’s dense populations, even a moderate eruption could have severe consequences. Ultimately, the research aims to improve understanding of volcanic cycles and enhance the ability to detect warning signs well before future catastrophic eruptions occur.