The crystals that could help predict volcanic eruptions

It is one of nature’s most destructive acts – and one of its most unpredictable; when an active volcano re-activates, spewing molten lava and threatening people living in its vicinity.

Scientists based in Ireland and Australia have discovered "seemingly unremarkable" crystals deep within the earth surface could help predict volcanic eruptions with much better accuracy, and in a more timely fashion.

They may look "inconspicuous and pretty unassuming", but small crystals – known as clinopyroxene – in volcanic rocks, especially magma and lava, may hold the key to better understanding how volcanoes recharge and erupt, according to Prof Balz Kamber of Trinity College Dublin.

With Dr Teresa Ubide, now based at the University of Queensland, they discovered the crystals' ability to record different stages of volcanic activity in much the same way a tree's rings can tell its natural history.

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“The new approach could be welcome news for the hundreds of millions of people who live close to active volcanoes. Our research is a significant step forward in understanding the processes that lead to eruption but more work is clearly needed,” Dr Ubide said.

Their research is published on Tuesday in the journal Nature Communications.

The crystals form inside the volcano when molten rock magma starts moving upwards from depths of up to 30 km towards the Earth’s surface. The crystals are carried in the erupting magma, and they often continue to grow as they are being transported. Significantly, they also change in composition on their way to the surface.

Prof Kamber and Dr Ubide used a laser technique to examine the inside of these crystals in their various forms. They focussed on tiny trace elements, notably Chromium, which generates distinctive images depending on stage of development that can be recorded using a spectrometer.

Growth layers

“What we discovered is that the crystals contain a memory in the form of growth layers that look similar to tree rings. Reading the history from these layers may lead to more effective volcanic hazard monitoring, including the likelihood of dormant volcanos becoming active,” Prof Kamber explained.

Dr Ubide said: “They essentially ‘record’ the processes right before the eruption starts. In the studied volcano, we found that the arrival of new magma at depth triggers an eruption up to 90 per cent of the time – and within only two weeks.”

At present, the world’s most dangerous volcanoes are monitored on a continuous basis at their surface and from space. In stages activity builds with magma pushing into the volcano. As it inflates, the questions usually asked are “should you get worried? Should the area be evaluated?”

There is a risk that waiting until the lava comes out may be too late, Prof Kamber added.

Their research when combined with monitoring of small nearby earthquakes and indication of depth where the growth path is occurring adds up to a “powerful tool” to predict what is likely to happen and when.

The research was conducted on Mount Etna, in Sicily, which is Europe's most active volcano. They are now planning to expand the approach to other volcanoes around the world, and to combine the information with geophysical signs of magma movement.

Dormant

It remains very difficult to predict volcanic eruptions, as evidenced by the eruption at Mount Agung in Bali, which started last November after two months of precursory earthquakes.

It led to the evacuation of over 70,000 people and caused massive disruptions in air traffic and tourism, affecting over 100,000 travellers.

Prof Kamber, who is professor of geology and mineralogy at TCD, said the new approach may also prove useful for studying volcanoes that have remained dormant, such as the currently erupting volcano on Kadovar Island, Papua New Guinea.

“For many volcanoes there is no eruption history, but geologists can collect lavas from past eruptions and study their crystals.”

Dr Ubide noted: “Knowledge on the typical mechanisms triggering past eruptions, the depth at which they occur and the lead times to eruption could advise future volcano monitoring efforts.

“The crystal record could provide new insights on the hazard potential of future earthquake signals and the time available for emergency planning.”

The authors conclude in their paper “such studies have potential to help decode eruption-triggering mechanisms, depths and timescale”.

The bulk of their research was conducted in TCD, where Dr Ubide was based before being appointed to a new role in Australia – the project was funded mainly by Science Foundation Ireland.

Dr Ubide's location meant the next targets for further developing their research and testing predictability would be in Indonesia and the Philippines; some of the most dangerous places in the world in terms of volcanic activity. Other areas of strong interest included the Azores and Canary Islands, Prof Kamber added.