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Scientists To Hunt For Rare Seafloor Hot Springs

1 May 2002

New Zealand, American, and Japanese scientists will leave this week on a two-week voyage to probe seabed thermal activity around 11 newly-mapped submarine volcanoes between the Bay of Plenty and the Kermadec Islands.

Using new equipment deployed from the research ship Tangaroa, they will focus on a little-studied area of the Pacific Rim of Fire volcano belt to determine the extent of mineral-rich thermal emissions from the seabed.

Two of the undersea volcanoes they plan to investigate are believed to be similar in size to Mt Ruapehu.

The survey area, within New Zealand's Exclusive Economic Zone, extends from Brothers Volcano, 400km northeast of White Island, to Curtis Island at the southern end of the Kermadec Islands - a distance of 500km.

Led by the Institute of Geological and Nuclear Sciences Limited (GNS), the research follows on from a 1999 survey closer to the Bay of Plenty coast that found seven of 13 submarine volcanoes were hydrothermally active.

" We suspect there are about 90 submarine volcanoes between New Zealand and Tonga, but it's not known how many are active," project leader Cornel de Ronde of GNS said.

" Results from our 1999 survey surprised everyone. The level of seafloor hydrothermal activity was far greater than anyone had expected, and greater than has been seen in many parts of the world. We found extremely rich emissions of iron and manganese, plus deposits of copper, zinc, lead and gold."

The emissions are dense plumes of dissolved minerals pouring from "black smoker" chimneys that grow vertically from the seafloor. The chimneys host a rich assortment of unusual animals, some of which are new to science.

The scientists will tow a newly built ocean "sniffer" that can detect volcanic plumes and hydrothremal activity coming up from the seafloor.

It is so sensitive, it can detect dissolved helium thousands of kilometres from its source.

Displaying its measurements in real-time on the ship's computers, it searches for telltale chemical compounds and characteristics in the seawater. These include hydrogen sulphide, methane, acidity, temperature, salinity, and light-scattering.

" We know immediately when we get close to a volcanic plume. The computer displays just go wild, " said Dr de Ronde, a marine geologist.

The scientists then criss-cross the area for detailed sampling of the plume. They also collect seawater samples for later analysis of iron, manganese, helium, and other elements.

The volcanoes northeast of New Zealand emit their plumes much shallower in the ocean than elsewhere in the world. Longterm aims of this research are to determine the effect of these emissions on ocean chemistry and the marine food chain.

Using elements in the plumes as a tracer, scientists may also be able to learn more about ocean currents.

The project follows a NIWA voyage in April during which the 11 submarine volcanoes were mapped precisely for the first time.


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