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Lake Rotorua survey shows activity

NZ NewswireNZ Newswire 11/11/2016

The lake was previously surveyed in 2005 by the University of Waikato. © David Davies/Press Association The lake was previously surveyed in 2005 by the University of Waikato. Scientists are pleased with how work is going on mapping the floor of Lake Rotorua where there is significant hydrothermal activity.

Lake Rotorua formed within a large volcano that last erupted 240,000 years ago.

The survey of the lake floor, which is being conducted by members of the Royal New Zealand Navy's Littoral Warfare Unit from October 17 to November 18, has covered about 40 per cent of the lake floor.

"We have found significant evidence of hydrothermal activity throughout the lake," says Lieutenant Commander Tim Garvan, who is leading the operation.

Marine geologist Cornel de Ronde, from GNS Science, says pockmarks indicate that gas is being discharged through the lake floor, while gas and hot water escaped from the vents.

The pockmarks, circles several metres wide, are formed as a result of gas being discharged through the lake floor, Dr de Ronde said.

"Many of them appear in a linear pattern, suggesting they may be related to underlying faults."

Survey results will provide GNS Science with a high-resolution map of Lake Rotorua's floor and geological features.

The work is the first step in a series of surveys that will ultimately determine how much heat is being discharged through the lake floor from an underlying magma source, with the results feeding into a long-term hazards assessment of the area.

The lake was previously surveyed in 2005 by the University of Waikato.

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