A huge chunk of the earth's crust missing?

London, Mar 6: A team of British scientists set sail toexamine why a huge chunk of the earth's crust is missing, deep underthe Atlantic Ocean a phenomenon that challenges conventional ideasabout how the earth works.

The 20-strong team aims to survey an area some 3,000 to 4,000metres deep where the mantle the deep interior of the earth normallycovered by a crust kilometres thick is exposed on the sea floor.

Experts yesterday described the hole along the mid-Atlantic ridgeas an ''open wound'' on the ocean floor that has puzzled scientists forthe five or so years that its existence has been known because itdefies existing tectonic plate theories of evolution.

''We know so little about it,'' said Bramley Murton, a senior research scientist at Southampton's National Oceanography Centre.

''It's a real challenge to our established understanding of whatthe earth's surface looks like underneath the waves,'' he told Reutersby telephone from the brand new, hi-tech British research ship RRSJames Cook.

Mid-ocean ridges are places where new oceanic crust is born, with red-hot lava spewing out along the seafloor.

What scientists are keen to know is whether the crust was rippedaway by huge geological faults, or whether it never even developed inthe first place.

The primary motivation for the project was to understand how the earth continues to evolve.

''The area that we are looking at is part of a mountain range thatspans thousands of square kilometres, but we are beginning to realisethat there are probably millions of square kilometres where the oceanfloor is missing,'' Murton said.

The six-week mission, led by geophysicist Roger Searle of DurhamUniversity and Chris MacLeod of Cardiff University's School of Earth,Ocean and Planetary Sciences, will recover sample cores of rock bydrilling into the mantle using a rig lowered on to the sea floor.

Asked if the discovery posed a threat to the environment, Murtonreplied: ''It's not problematic for the earth because it is a naturalearth process but in terms of knowing how the earth works and howthe world is put together it is important.'' Murton also said theexpedition would shed light on the composition of sea water amongstother initiatives.

Crust formation is a fundamental mechanism of the earth which affects the chemistry of the world's oceans.

Reuters>