Scientists have found unusually hot water, at temperatures of more than 100 degrees Celsius, close to the Earth’s surface in New Zealand.
Water at temperatures of more than 100 degrees Celsius is normally only found at depths of over three kilometres, but in this case it was encountered at just over 600 metres depth.
The researchers made the discovery while boring almost a kilometre into the Alpine Fault, the major tectonic boundary between the Australian and Pacific plates — running the length of the country’s South Island.
Temperature and fluid pressure conditions control rock deformation and mineralisation on geological faults, and hence the distribution of earthquakes.
The team was working to better understand what happens at a tectonic plate boundary in the build-up to a large earthquake.
The Deep Fault Drilling Project (DFDP) borehole was drilled at Whataroa to the north of Franz Josef Glacier and discovered extremely hot, highly pressured groundwater flowing near to the fault line.
“The temperature profile of the DFDP borehole is really exciting,” said Damon Teagle, Professor at University of Southampton in Britain.
In a study published in the journal Nature, the researchers used computer models to show these high temperatures result from a combination of the uplift of hot rocks along the tectonic plate boundary and groundwater flow caused by high mountains close to the Alpine Fault.
“The Alpine Fault extends over such a massive distance, it is visible from space. It is potentially New Zealand’s greatest geohazard, failing in the form of large earthquakes about every 300 years,” Teagle, who leads the Southampton group involved in the project, said.
“With the last event occurring in 1717 AD, there is a high probability of a major (magnitude 7 to 8) earthquake in the next 50 years — making research into its behaviour all the more important,” Teagle added.