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High geothermal temperatures found deep below the Southern Alps

Staff Writer |
The Alpine Fault is one of the world's major geological features and its tectonic movements have created the more than three-kilometre-high Southern Alps.

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But it's a discovery just half a kilometre deep that has scientists stirring.

A collaboration by a team that drilled into the fault revealed water at 630 metres that was hot enough to boil.

Similar geothermal temperatures are found normally at depths greater than three kilometres, or in association with active volcanoes.

"The conditions we've uncovered are extreme by global standards and comparable to those in major volcanic centres like Taupo—but there are no volcanoes in Westland," says Victoria's Professor Rupert Sutherland

"Nobody on our team, or any of the scientists who reviewed our plans, predicted that it would be so hot down there."

Rupert worked with more than 100 scientists from 12 countries as part of the Deep Fault Drilling Project, jointly led by Victoria, GNS Science and the University of Otago.

In 2014, the team drilled into the Alpine Fault at a site near Whataroa, a small township north of Franz Josef Glacier.

The team identified the Whataroa site as the best place in the world to understand what a fault looks, feels and sounds like just before an earthquake occurs.

The Alpine Fault is known to rupture in magnitude 8 earthquakes approximately every 300 years and last ruptured in AD 1717.

The team hadn't expected to find such extreme temperatures and the potential for large geothermal resources in the area.

"The geothermal environment is created by a combination of tectonic movement and groundwater flow. Slippage during earthquakes has uplifted hot rocks from about 30 kilometres deep, and the rocks are coming up so fast that they don't get a chance to cool properly," explains Rupert.

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