Eruption warning clues may be possible to ID

‘‘That eruption was roughly five times larger than the 1980 eruption of Mt St Helens.’’ Tarawera researchers

Analysis of crystals from a massive central North Island eruption 700 years ago could help make it easier to know when a volcano is at increasing risk of erupting.

A team of researchers from Canterbury University and universities in the US and Singapore analysed zircon crystals extracted from volcanic rocks around the slopes of Mt Tarawera, deposited during the Kaharoa eruption of around 1314.

That eruption was roughly five times larger than the 1980 eruption of Mt St Helens in the northwestern US.

The reasearch results suggest the magma below the Taupo Volcanic Zone was only subjected to high temperatures of 650-750C for a period of years to a few centuries.

Study co-author Kari Cooper, professor of earth and physical sciences at the University of California, said magma was not a seething mass of molten rock but mostly solid and crystalline, with a little liquid seeping through it.

To create an eruption, a certain amount of that solid, crystalline magma had to melt and start to move, possibly by interacting with hotter liquid elsewhere in the reservoir.

It may be possible to identify volcanoes at risk of eruption by looking for those where magma was most mobile.