The sleeping dragon: Researchers find blazing heat beneath the Southern Alps
Researchers have found some of the most extreme underground conditions anywhere on Earth beneath the Southern Alps, including temperatures similar to that of an active volcanic zone.
The surprise discovery could have economic implications for the area, and may give clues as to the conditions of a major fault prior to a significant rupture.
An international research team has discovered "extreme" geothermal conditions deep beneath the mountains, according to research published in the Nature journal on Thursday.
Temperatures measured near the surface were similar to those found in active volcanic zones such as Taupo – yet there are no volcanoes in Westland.
The research team – led by GNS Science, Victoria University of Wellington and the University of Otago, comprising more than 100 people from 12 countries – drilled a borehole nearly 900 metres deep at a site near Whataroa in Westland.
They were trying to establish the conditions of a major fault prior to a significant rupture.
The alpine fault is highly predictable, producing a magnitude-8 earthquake about every 300 years. The last such earthquake was 300 years ago.
At 630m deep, they measured water temperatures of 100 degrees Celsius, hot enough to boil. They expected temperatures of less than 40C.
Drilling further, they determined the borehole's geothermal gradient – how quickly temperature rises as you go deep into the earth – was unlike any known active fault in the world.
"Nobody on our team, or any of the scientists who reviewed our plans, predicted that it would be so hot down there," said lead scientist Professor Rupert Sutherland from Victoria University of Wellington.
He said they found some of the "most extreme underground conditions on the planet"; the conditions were similar to that of boreholes drilled directly into volcanoes.
It was likely a mixture of two processes, he said. Rocks of about 550C are uplifted from 30 kilometres deep with such speed they do not cool down.
Fractured rocks allowed water to seep into the mountains beneath valleys, further uplifting heat, before being flushed by rain and snow.
"This geothermal activity may sound alarming but it is a wonderful scientific finding that could be commercially very significant for New Zealand," Sutherland said.
The next step would be to determine how extensive the geothermal resource is and whether using it is viable.
Project co-leader Dr Virginia Toy, from the University of Otago, said the discovery was unexpected, and no major faults worldwide were known to have such a high geothermal gradient.
"It turns out this is just as hot as the Taupo volcanic zone, which is virtually an active volcano. It's astonishing."
It was not yet certain whether it had implications for the nature of a surface rupture, but it was possible, she said.
The next step would be to do more scientific work and establish a business case for how to use the geothermal resource.
"What we need to do next is to evaluate the scientific information around how widespread this resource is, how long lived it is, if we started to exploit it would it continue.
"There's a lot of business case analysis work that needs to be done before you can make use of something. It's great to be excited, but you have to be realistic."
Uses could include a geothermal power plant, similar to an aluminium smelter. It could also have tourism benefits, harnessing the water for hot pools or powering cellphone towers.
New Zealand pioneered the use of geothermal power, which is a reliable source of renewable energy. It makes up about 13 per cent of energy production and is mostly concentrated near Taupo.
Development West Coast chief operating officer Warren Gilbertson said it could be a great opportunity for a local industry.
"The location of geothermal activity and its possible benefit and association to the dairy and tourism sectors provide real opportunities from an economic perspective," he said.
West Coast authorities have been exploring new economic opportunities due to the downturn in coal mining.