Really Down Under, Down Under

Forest and Bird, Issue 291, 1 February 1999, Page 16

Really Down Under, Down Under

ew Zealand scientists have recently had a share in drilling the ocean depths of the subantarctic, exploring the Earth’s past. Sailing with the international research vessel, JOIDES Resolution, three earth scientists have taken part in the 181st leg of the International Ocean Drilling Programme which has been taking rock cores from the floor of the ocean for the past 34 years. "The ocean depths are the frontier for new scientific discoveries that even now are revolutionising our understanding of how the Earth systems work, says Dr Bruce Hayward, James Cook Research Fellow and paleontologist working from Auckland University. The southern voyage revealed substantial information about how New Zealand was formed, and its geological history over millions of years. The JOIDES Resolution has the technology to drill even in high seas, putting down a flexible drill pipe through a pool in the middle of the vessel. Off New Zealand she was drilling into ocean floor lying at depths of from 400 to 4500 metres. The coring assembly, which gathers material from below the ocean, is first let down inside the pipe which is 20 centimetres in diameter. Then the core drilling is done, bringing up samples which may come from up to a kilometre below the floor of the ocean. Off the New Zealand coast

seven sites were drilled, each chosen largely on the basis of scientific work by Dr Lionel Carter, a marine geologist with the National Institute for Water and Atmospheric Research. Previously this work had depended on the results of seismic surveys and the samples gathered by the use of smaller oceanographic vessels. These penetrated only a few metres into the seabed producing samples from only the last 100,000 years. The JOIDES Resolution could reach down through the deposits of millions of years. With its satellite navigation and surrounding battery of 12 thruster motors, the ship could hold its position and keep on drilling in all but the wildest seas. Drilling to the east of New Zealand, the JOIDES Resolution worked through deposits left by the giant ocean currents which circulate the world’s oceans. Here, deep below the sea, are layers of material which reflect the geological history of ancient New Zealand — material swept away as the land rose and fell, along with the ash from the giant earth-making volcanoes. On board, Bruce Hayward and Gary Wilson of the Institute of Geological and Nuclear Sciences worked on determining the ages of the layers of mud as the cores brought samples to the surface. One hole probed through mud accumulated on the ocean floor

65 million years ago. This was the time when a giant meteorite is believed to have hit the Earth, contributing to the extinction of the dinosaurs and 80 percent of life on land and in the sea. Another core, drilled 450 kilometres northeast of Chatham Island, revealed 600 metres thickness of mud and ooze that had accumulated without a break over the past 20 million years. In it was a complete record of the many occasions when the Earth’s magnetic poles had switched back and forth between north and south. It also records a 20-million-year history of the world’s constantly changing climate, including the dramatic cold and warm cycles of the Ice Ages. The sequence of New Zealand’s great volcanic eruptions could also be traced in cores. Some 600 kilometres east of Gisborne, under 4500 metres

of water, there were 139 distinct volcanic ash layers from the last 12 million years, According to Dr Hayward, they came initially from the Coromandel region, then the Kaimai Ranges, and in the last million or two million years from the Taupo-Bay of Plenty area. Altogether 4 kilometres of cores were taken and shipped to Texas where they are held in refrigerated stores for sampling and study. The Ocean Drilling Programme costs $NZ80 million a year and is funded 60 percent by the United States National Science Foundation, and the remainder by 20 other countries, not including New Zealand. The ship’s complement is 63 crew and 50 scientists and technicians from various parts of the world. The material gathered is available to all scientists for research, including those from New Zealand.