Is massive magma build-up in New Zealand the start of a new volcano?

Beneath Matata, a small coastal town 125 miles from Auckland, on New Zealand’s North Island, scientists recently discovered a massive magma build-up, possibly signaling the beginnings of a new volcano.

But oddly, this magma chamber is nowhere near an active volcano.

According to geophysicist Ian Hamling, since 1950 an incredible influx of magma – enough to fill 80,000 Olympic-sized swimming pools – has accumulated beneath the small New Zealand town, pushing up the surface of the ground by 40 cm (16 inches).

In a paper published Saturday in the online journal, Science Advances, Mr. Hamling describes discovering the enormous magma chamber as, "quite a big surprise," stating that while New Zealand contains a great deal of volcanic activity, it is unusual to find a developing chamber of magma so far removed from any active volcanos.

Hamling and his team had been studying the Taupo Volcanic Zone (TVZ), which runs down the center of New Zealand's North Island and has seen 25 large-scale volcanic eruptions in the past 1.6 million years and currently is home to many spectacular volcanic features such as bubbling hot pots and frequent eruptions at Whakaari – a small active volcano 30 miles from the east coast of the North Island.

The team's focus was on ground motions throughout the TVZ, searching for volcanic activity in an area that had been believed to be subsiding because of magma draining from an underground chamber. However, shifting the examination, the team discovered the ground beneath Matata, a town with a population of 650 people, had been rising yearly since 1950 and the rate of increase had been growing substantially through the beginning to mid-2000s, triggering thousands of small earthquakes initially believed to be associated with tectonic shifts. 

Utilizing satellite data, Hamling and his team were able to follow the development of minor ground shifts, measuring minute horizontal and vertical changes in the coastal land levels, demonstrating the shifting nature of subsurface magma within the TVZ.

Calculations imply that approximately 9 million cubic meters of magma – or 3,600 Olympic-sized swimming pools worth – pressed into the Earth's crust each year during the chamber's peak growth period.

Over time, the pooling magma within the massive underground chamber could either rise towards the surface after hundreds or thousands of years, or the magma chamber could eventually cool and harden. Though Hamling says that because the developing magma chamber is located 6 miles below Earth’s surface, it will not likely develop into a volcano within his lifetime.

"When you compare it to other places, like Yellowstone, we're smaller than that. But it's still pretty significant." Hamling said, referring to recent developments where seismologists from the University of Utah discovered an enormous magma chamber beneath the National Park containing enough molten rock to fill the entire Grand Canyon 11 times; thus designating much of Yellowstone a "super volcano," with its geysers and regular minor earthquakes.

As reported by Scientific American, this recent development in New Zealand is not the first suggestion that magma is pressing into Earth's crust in locations other than directly beneath an active volcano. Matthew Pritchard, a geophysicist at Cornell University refers to such examples as "zombie volcanoes" – because they show signs of life where it should be dead – having discovered similar examples in the central Andes mountain range.