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Scientists to explore Taupo lakebed in sub - 29/07/1998

Scientists are going to explore the bottom of Lake Taupo in a submersible to find out more about Taupo's violent volcanic history and a geothermal system under the lakebed.

Taupo Sub

It will be the first time a submersible has been used for research in Lake Taupo.

The Institute of Geological & Nuclear Sciences Limited has gained approval for the project from the Tuwharetoa Maori Trust Board, the owner of the study area. The agreement between the Institute and the Board cements a joint working relationship for the project.

The agreement also covers the future relationship between the two groups with provision for closer partnerships in areas of mutual interest such as environmental issues, geological hazards, and geothermal energy.

Weather permitting, the two-person German submersible will make two four-hour dives a day over four days in October. Its dive target area will be the Horomatangi Reefs on the eastern side of the lake.

'' The reefs are the site of the huge Taupo eruption of 181AD, acknowledged as the world's most violent eruption in the past 5000 years. It produced about 50 cubic kilometres of ash and pumice and a 50km-high eruption column,'' project leader and minerals geologist Cornel de Ronde said.

Immediately after the 181AD event the eruption vent was plugged up by solid rock. But surrounding the vent is a large area of pumice and soft sediments about 3km deep.

The area has puzzled scientists for decades, but as it is one of the deepest parts of the lake at 160m, it is accessible only in a submersible.

Scientists are fairly sure the area contains an active geothermal field, including hot water jets possibly gushing out of hydrothermal "chimneys" -- the submarine equivalents of geysers like those in Rotorua. It is also possible metal-rich minerals might occur around these hydrothermal vents as they commonly do at hot-spots on the seabed off the Bay of Plenty coast and a number of other areas worldwide.

'' We will be exploring an area where no-one has ever been before so we're unsure what we'll find, but the submersible gives us the best chance we've ever had at uncovering Taupo's deep secrets,'' Dr de Ronde said.

'' Our aim is to collect and analyse the fluids and gases gushing out of the submarine vents. We'll also be collecting rock and sediment samples for chemical analysis and documenting lakefloor structures with a digital video.''

Results will be compared with similar analyses of seawater-dominated thermal vents near White Island, off the Bay of Plenty coast, and with on-land geothermal fields such as Wairakei. Scientists anticipate the information will help in improving the understanding of the evolution of New Zealand's geothermal fields. It should also provide new insights into the 1800-year-old Taupo eruption.

The Tuwharetoa Maori Trust Board said it was particularly interested in seeing the lakebed under what is one of Taupo's most productive fishing grounds.

" Protection of the site, which is revered in Tuwharetoa history, is of utmost importance to the Board, '' a Board spokesman said.

The sub, known as JAGO, has a maximum operating depth of 400m. Its two large acrylic windows give the crew excellent visability and it is equipped with a large hydraulic arm for retrieving samples and manipulating objects. Typical applications include photo documentation and collection of organisms, sea-bottom surveys, salvage and recovery, and environmental studies.

The 3.2m-long, 3-tonne JAGO is scheduled to arrive in Wellington on its mother ship, the research vessel Sonne, on October 15. It will be taken to Lake Taupo by truck.

For more information please contact:
John Callan
Communications Manager
Institute of Geological & Nuclear Sciences Limited
Ph: 04-570-1444 (w)