The New Zealand town sitting on a growing volcano

Scientists say they have discovered a magma buildup near a New Zealand town that could signal the beginnings of a new volcano – although they’re not expecting an eruption any time soon.

Geophysicist Ian Hamling said that since 1950, enough magma to fill 80,000 Olympic-size swimming pools has squeezed up beneath the surface near the coastal town of Matata, about 200km (120 miles) south-east of Auckland. The discovery explains a spate of earthquakes between 2004 and 20011.

A paper published on Saturday in the online journal Science Advances outlines the findings. Hamling, the paper’s lead author, said that while other parts of New Zealand have active volcanoes, there have been none near Matata for at least 400,000 years.

“It was quite a big surprise,” he said.

Using GPS data and satellite images, the scientists said they discovered an area of land about 400 sq km (154 sq m) had risen by 40cm (16in) since 1950.

Hamling said a period of quick uplift between 2004 and 2011 was likely to have triggered thousands of small earthquakes. Scientists had previously thought tectonic shifts caused the quakes.

Hamling said the magma remained about 10km (six miles) below the surface, deep enough that he didn’t expect a volcano to develop within his lifetime. He said a volcano could develop over hundreds or thousands of years, or the magma could eventually cool and harden.

Matata is home to about 650 people. Hamling said he hoped further study would allow scientists to develop a warning system for earthquakes in the area. He said the quakes were probably triggered by magma stressing and breaking rock.

Hamling said it was unusual worldwide to discover magma build-up in an area with no volcanoes. He said modern equipment allowed them to accurately measure tiny horizontal and vertical changes in the coastal land.

Just over half of the area studied is offshore, however, and Hamling said the scientists needed to rely on inferences from what happened on the land to gauge the changes underwater.

Victoria Miller, a volcanologist with Geoscience Australia who was not involved in the research, said the location was of interest because it was outside an active volcanic area.

“The scientific analysis seems robust and notes the limitations of modelling an offshore source,” Miller wrote in an email.