The sea reveals what lies beneath
A new programme to drill into the Earth hopes to penetrate further than ever before
By Steve Jones
8:52AM BST 03 Sep 2013
The deepest hole ever made is more than 40 years old, and quite dead. In 1970, the Soviet Union began to drill on the Kola Peninsula, close to the Finnish border, in an attempt to penetrate the skin of the Earth. Ten years later, the drill passed the six-mile record then held by a hole in Oklahoma made by an oil company, which failed when its drill bit hit a lake of molten sulphur. Five more years took it to seven-and-a-half miles – but then the temperature rose so high that to go any further would have melted the bit. In 2008, the money ran out and the site was abandoned (although some fundamentalists still cite the hoax that the drill was stopped because it had broken into Hell itself). 8)
Now, a new programme of ocean drilling is under way, attempting to reach parts of the planet’s interior never before penetrated. The problem with drilling on land is that the Earth’s outermost layer – the crust – is so thick that there is little chance of getting through.
Under the sea, however, its intimate secrets are easier to probe. A century ago, the Croatian meteorologist Andrija Mohorovicic was studying the shock waves made by earthquakes as they passed through the continents. He noticed that the waves travelled much faster through the rock about 35 miles below the surface than they did above that depth. That shift – the Mohorovicic discontinuity, or “Moho” – hinted that the Earth has distinct layers of rock above its liquid metallic core, with the Moho forming the boundary between the outer crust (which makes up less than one hundredth of its mass) and an inner zone called the mantle.
Beneath the deep oceans, where the surface is younger and thinner as it has been extruded from the molten depths, the Moho may be less than four miles down. In 1957, the Americans set out to penetrate it in a deep trench off Mexico, and did manage to extract a short core of mantle. However, the project was plagued with difficulties in keeping the ship in place and manipulating the drill through two miles of water, and was abandoned.
With GPS, and today’s oil-well technology, both those problems have been solved – so the International Ocean Discovery Programme has set out to break through the Moho and find what lies below. It is now investigating sites off Hawaii, California and Baja California, to find the right balance between new, thin (but hot) crust and older, thicker, but cooler material that will not melt the drill. Already the Baja hole has reached roughly a mile down.
One aim is to work out the role in the global carbon cycle of the liquid that bubbles from the mantle at the ocean ridges; another is to insert sensors into the hole to check the temperature, pressure and intestinal movements of our planet. The geologists hope to examine the mantle’s balance of metallic elements, which may be depleted in platinum, gold, cobalt and others that have been sucked in by the liquid iron core.
Biologists are involved, too. Already, single living cells have been found more than a mile below the sea floor, and we know that bacteria from ocean vents can survive at 115C; which means that, in principle at least, they or their relatives could exist three miles below the surface. It might hint at what the first life, on a searing-hot planet more than four billion years ago, looked like.
As Roy Livermore points out elsewhere on this page, plate tectonics has explained many once-baffling observations about the Earth. Fifty years after Drummond Matthews and Frederick Vine’s discovery, these giant drills are revealing more truths about our planet, and this time in 3D.
http://www.telegraph.co.uk/science/stev ... neath.html
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