A study of crystals from an eruption in New Zealand about 700 years ago found a pattern in the thermal history of magma that reveals when the next one is due.
The analysis found it went through a comparatively ‘cool’ period for thousands of years before heating up.
Once temperatures reached 750 degrees Celsius, it was a short amount of time – decades or less – before an eruption occurred.
Geologist Professor Adam Kent, of Oregon State University, said: “Mobility in magma is a function of temperature and most of the time when it is sitting there in the Earth’s crust under the volcano it is cool.
“Of course, cool is a relative description since it is still some 650 degrees Celsius. I would not put my finger on it.
“But to erupt onto the Earth’s surface magma needs…