Scientists seek better predictions of volcanic behaviour

Mt Tauhara, overlooking Taupo. File photo / Greg Bowker

Scientists may be able to better predict how quickly some volcanoes erupt after studying material thrown out of Mt Tauhara, overlooking Taupo.

The imposing mountain, formed about 65,000 years ago, had some "peculiar aspects" which have allowed scientists to gain new knowledge about volcanic eruptions, said Victoria University researcher Dr Monica Handler, who has been part of a team studying the volcano.

Research by the team has found it took as little as two months to up to two years for magma to form under the volcano - and only two to three weeks for the magma to rise to the surface and erupt.

By understanding the characteristics of the magma erupted from Tauhara, scientists were better able to predict the behaviour of volcanoes of similar compositions, which also occur in continental volcanic regions such as the Cascades and Andes ranges of North and South America.

"If movement is detected underground, we now have a better understanding from Tahara's example, how these types of volcanoes can work and are better able to predict how quickly the magma can reach the surface of the earth and erupt," Dr Handler said.

"Only minor amounts of the type of magma erupted have been found in the Taupo Volcanic Zone and the individual crystals in the rocks erupted by Tauhara should not normally be found together in the same rock."

To understand how the unusual magma formed, the team carried out investigations on individual crystals found in the rocks using the state-of-the-art geochemistry laboratory at Victoria University.

The mineral chemistry gave information about the composition of the molten magma it grew in, as well as the pressure and temperature at which it formed.

This provided information about what depths the magma formed and was stored. And also, importantly, for how long.

"Our data show that different magma batches took from as little as two months to up to two years to form under Tauhara volcano. We were also able to calculate that it took only two to three weeks for the magma to ascend to the surface and erupt."

"The more we understand how the different types of volcanoes work, the better we're able to monitor them. If we start to see evidence of activity we may be able to identify the pattern and understand what might happen and how to mitigate the results of that."

People live in close proximity to the Taupo Volcanic Zone, so it was vital to have the best information possible about the different types of eruptions that can occur, she said.

The work, undertaken by Master of Science student Chelsea Tutt, with the supervision of Dr Handler, Dr Marc-Alban Millet, and Professor Joel Baker, is part of a broader research programme, applying the laboratory facilities at Victoria University to problems of understanding the rare but hazardous eruptions in the central North Island.

The findings add to a global understanding of volcanoes and their timeframes for erupting, which is critical to predicting how much of a risk they pose.