Can crystals tell us about volcanoes?

Tiny crystals could provide new insights into past volcanic eruptions and help predict future ones, according to a new study from Stanford University in the US.

In this case, the millimetre-size crystals were of the mineral olivine formed during a violent eruption of the Kilauea Volcano in Hawaii in 1959, and they were used to test computer models of magma flow.

“We can actually infer quantitative attributes of the flow prior to eruption from this crystal data and learn about the processes that led to the eruption without drilling into the volcano,” says Jenny Suckale, lead author of a paper in Science Advances.

The crystals were found in scoria, a dark, porous rock that forms when magma containing dissolved gases cools.

Analysis revealed they were oriented in an odd, but surprisingly consistent pattern, which the researchers hypothesised was formed by a wave within the subsurface magma that affected the direction of the crystals in the flow.

When a volcano erupts, the liquid magma – known as lava once it reaches the surface – is shocked by the cooler atmospheric temperature, quickly entrapping the naturally occurring olivine crystals and bubbles. The process happens so rapidly that the crystals cannot grow, effectively capturing what happened during eruption.

The new simulation provides a baseline for understanding the flow of Kilauea’s conduit, the tubular passage through which hot magma below ground rises to the Earth’s surface.

Analysis indicates the odd alignment of the crystals was caused by magma moving in two directions at once, with one flow directly atop the other, rather than pouring through the conduit in one steady stream.

Researchers had previously speculated this could happen, but a lack of direct access to the molten conduit barred conclusive evidence, according to Suckale.

“This data is important for advancing our future research about these hazards because if I can measure the wave, I can constrain the magma flow – and these crystals allow me to get at that wave,” she says.

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