Crystals and rich ores drawn from deep inside active volcanoes might lead the way to a better future

I can remember my first ever geology class, at an age in school when I didn’t even know what the word geology meant. The teacher asked us all to draw a volcano, so we took our notebooks out and drew a typical triangle shape, with some lava, the sun, some trees, whatever. Our teacher then drew the same thing, the triangle, at the very top of the whiteboard, and said, “This is great, but watch this.”

She then started drawing a vast maze of conduits and magma chambers below the surface – everything that was happening deep inside the volcano, showing how the magma controls the development of eruptions.

Understanding what happens deep inside a volcano is crucial to understanding the development of eruptions at the surface.

I was totally hooked. From that day I have wanted to be a volcanologist.

Understanding what happens deep inside a volcano is crucial to understanding the development of eruptions at the surface. Of course, we can’t go inside active volcanoes. But we can use our science to investigate. We’ve discovered that their complexity is enormous and the complexity is different depending on the setting.

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Typically, we find volcanoes in three tectonic regions on Earth. One is where two tectonic plates move towards each other – that’s called an arc system. Another is where two tectonic plates move apart from each other – that’s a mid-ocean ridge. And another one is in the middle of nowhere geologically speaking, and that’s where we have a hotspot, like Hawaii. The architecture of the magma-feeding systems can be quite different in these different geological settings.

We can even pinpoint the process that triggered the eruption as a means to better understand future activity. This way we can prepare better forecasts.

The magma that makes it all the way to the surface and generates lava is a mixture of liquids, gases, and crystals. The crystals are really cool – they’re like little heroes. They grow in the guts of the volcano and record everything that’s going on that we can’t see. They’re a bit like the rings of trees allowing us to see climatic variations over the ages. These crystals are tiny, like grains of salt, maybe the size of a chickpea if you’re very lucky. But in these crystals, you get layers that record what’s been happening in the magma system.

We analyse those crystals using a microscope and some sophisticated laboratory techniques. This way we can see the sequence of processes that happened in the volcano before the eruption – and importantly, we can see the very last process, the final ring on the crystal before the eruption.

We’ve been developing technology that uses lasers, like the ones we use for eye surgery, to remove a thin layer from these crystals. We then transport that material to an instrument that measures chemical composition: a mass spectrometer. From this, we can build an image of the chemistry of this resource, the crystals, as they grow. We can even pinpoint the process that triggered the eruption as a means to better understand future activity. This way we can prepare better forecasts.

The most breathtaking aspect for me is the sound. I remember when I first saw Stromboli erupt – the rumbling sound was just incredible.

That final ring in the crystal tells us that new magma entered the magmatic reservoir just before eruption. That new magma might be different in composition, with a high gas content that generated enough instability to push the magma up to the surface, a bit like when you shake a bottle of champagne.

Then we want to know at what depth this happened. How many kilometres inside the volcano was it? What were the timescales? This tells us how much time we have to react if in the future we detect magma movement at that depth – through earthquakes, for example. That’s the ideal scenario, building our understanding of how the volcano has behaved in the past so we can better understand its future activity.

I often go to volcanoes to collect samples, usually when they are quiet after an eruption. But I’ve also seen volcanoes erupting. The most breathtaking aspect for me is the sound. I remember when I first saw Stromboli erupt – the rumbling sound was just incredible. We often don’t hear it because it’s not safe to be so close. It makes you realise how alive the Earth is.

People are really suffering when the eruption is going on. So you need to get the signatures of not only the beginning of the eruption, but you also want to know when it’s going to end.

There are two big challenges ahead of us. In the same way that we use lasers to extract detailed information from crystals, we’re also developing laser technology to understand the chemistry of the liquids that bring those crystals to the surface.

Crystals allow us to look at what happened before an eruption. But if we can understand these liquids, we can try to understand what sort of processes extend volcanic activity – and terminate it. When you’re dealing with an eruption in an area that is populated, or has infrastructure, you want to know when it’s going to finish. People are really suffering when the eruption is going on. So you need to get the signatures of not only the beginning of the eruption, but you also want to know when it’s going to end.

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I’m also interested in the implications of volcanoes for obtaining the resources that we need for our renewable future. To transition to renewable energies, we need to source many more metals – copper, for example. It’s very interesting that in settings where tectonic plates move towards each other, volcanoes are primary factories of copper.

What is it that makes a volcano fertile for copper? Using our detailed analytical methods, we can better reconstruct the journey of the magma towards the surface, and how that journey married with the volcano’s ability, or not, to accumulate copper.

As told to Graem Sims

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