September 6, 2007. Copyright 2007, Graphic News. All rights reserved

EarthÕs mantle set to reveal its secrets
By Mark Rutter

LONDON, September 6, Graphic News:  The Japanese Agency for Marine-Earth Science and Technology (JAMSTEC) has announced that an attempt to drill right through the EarthÕs crust and into the mantle for the first time will start later this month.

The Integrated Ocean Drilling Programme (IODP) seeks to penetrate the elusive ÒMohoÓ, a boundary formally known as the Mohorovicic discontinuity, which marks the division between EarthÕs brittle outer crust and the hotter, softer mantle.

Deep-sea drilling vessel Chikyu will start drilling nearly 7km (4 miles) into the Earth in the relatively thin crust of the Nankai Trough in the Pacific Ocean. The expedition starts on September 21.

The crust forms a thin outer layer around the Earth. It consists of solid rock around 72km (45 miles) thick under the continents, but less than 8km (5 miles) wide under the oceans. Together with a thicker, solid upper mantle on which it sits, the crust is broken into huge slabs or ÒplatesÓ moving around very slowly like rafts on a liquid lower mantle. The lower mantle of rock is kept molten by the high temperature and pressure. Plate movement is usually very slow -- around 5cm (2in) a year -- although these movements can lead to the formation of mountain ranges, and trigger earthquakes and volcanic eruptions around the edges of the plates.

Drilling deep into the crust is fraught with danger due to the risk of hitting hot molten rock, or gas and oil fields, and the deepest hole drilled to date is only 2.1km (1.3 miles). The Chikyu, however, carries a drill designed around technology used by the oil industry. It is protected by a second pipe, filled with mud, which fits over the drill pipe and removes debris from the hole. A pressure release valve prevents blow-outs occurring if the drill encounters high pressure or gas and oil deposits. The IODP project involves the U.S. and much of Europe alongside JAMSTEC. Eventually it is hoped that the project will employ another one or two ships.

As well as research into plate movement -- or tectonics -- there are several practical reasons for carrying out the project, including the potential to save lives and to find new life. After Chikyu has drilled a hole, sensors will be put into it to monitor plate movement with the aim of being able to predict when and where an earthquake will strike, in time to clear people from the affected area. Current methods only warn of an imminent earthquake minutes before it happens, leaving too little time for evacuation. Another application of the research is to provide cores of deep rock and mud which it is hoped will provide clues to the climatic conditions on earth over thousands and even millions of years. These cores will also be analysed for signs of life. We know that microscopic bacteria can thrive at elevated temperatures found around hydrothermal vents on the sea floor and in hot springs. If bacteria are present in the deep crust and mantle, they are likely to posses unique properties such as enzymes resistant to boiling, and hence could be exploited by the biotechnology industry. It is expected to take over a year to drill into the mantle.
/ENDS