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NZ and US scientists probe East Coast history - 24/05/2004

American and New Zealand scientists have joined forces for a trailblazing study to understand the geological signals in sediment washed out from the Waiapu River on the North Island's east coast.

Steve Kuehl

The scientists will spend the next two weeks on the American research ship, Kilo Moana, deploying equipment, mapping the seafloor and collecting seabed sediment samples in Poverty Bay and near East Cape.

The project involves scientists from The College of William and Mary in Virginia, Geological and Nuclear Sciences (GNS), the National Institute of Water and Atmospheric Research (NIWA), and Landcare Research.

At just over 300 years old, The College of William and Mary is one of the oldest universities in the US. It is noted for its strong track record in earth and marine sciences.

The consortium of researchers will attempt to decipher the signatures in layers of seabed sediment that relate to earthquakes, volcanic eruptions, and extreme weather events in the North Island dating back many thousands of years.

The on-land signatures of these events are often partly or completely eroded away and therefore difficult to detect.

But signals from large geological, climatic and environmental events are stored in thick offshore sediment washed out by rivers. Deciphering these signals would give scientists another tool in understanding natural hazards and environmental changes.

The scientists expect to find human-induced changes, such as deforestation, recorded in the sediment layers.

The Waipaoa River mouth, south of Gisborne, and the Waiapu River mouth near Ruatoria are among the best sites in the world for the study. While modest and manageable in size, the sediment outwash over many thousands of years from the two rivers has been substantial.

The other site the consortium has chosen is the Fly River in Papua New Guinea. Both projects will run simultaneously.

US project leader, Steve Kuehl of the College of William and Mary, said another reason for the study was that sediment outwash from rivers worldwide was having a major impact on marine life. This included commercial fisheries.

Dr Kuehl said the layers of sediment could give clues to how carbon moved through natural systems and this could unlock information about how to deal with greenhouse gases.

The consortium's seabed instruments, which can store up to six months of data on board, would be retrieved from the Poverty Bay seafloor in October. Their measurements include current velocity and the amount of suspended sediment in seawater.

Known as the Source to Sink Programme, it is funded under the US National Science Foundation's Margins Programme. The Foundation for Research Science and Technology is helping to fund the New Zealand leg of the project.