Journey to the centre of the Earth begins at sea

Earth showing Mantle
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A pair of scientists are about to embark on a world-first mission to find out what's under the Earth's crust. Dr Damon Teagle, a geologist at the National Oceanography Centre at the University of Southampton, and Dr Benoit Ildefonse from Montpellier University in France, are leading a team which will aim to drill through more than eight kilometres of solid rock in the Pacific Ocean.

The aim of the mission is to retrieve samples of the boundary between the ocean crust and the mantle, known as the 'Mohorovicic' or 'Moho' for short. The start of this massive drilling will be made under the ocean off the coast of Costa Rica, and scientists hope to return never-before-taken samples from Earth's mantle.

It's not the first time drilling to the Earth’s mantle has been attempted - a team of American scientists attempted it in the 1960s - but Dr Teagle and Dr Benoit hope to be the first to manually extract samples - samples the experts say will rival moon rocks for importance and scarcity.

The drilling is expected to commence in 2020 off the western coast of Costa Rica in Central America, but preparatory exploration in the Pacific Ocean begins later in 2011. A Japanese ship equipped with six miles (ten kilometres) of drilling pipe will be used for the project.

At this location, in the middle of the ocean, the crust (the outermost solid shell of Earth) is thinner than elsewhere. In fact, it is only approximately 2.5 miles (4.0 kilometers) thick. Under the surface of the Earth is the crust, mantle, and core.

Dr Teagle says the value of knowledge about mantle rocks would 'provide insight into how current mantle processes operate—highly important in understanding the plate tectonics that drive many earthquakes, tsunamis, and eruptions'.

The 1960s project called 'Mole Hole', or in Russian 'Mohorovicic,' or 'Moho' for short, was conducted by Scientists from the former Soviet Union. When drilling stopped in 1994, the hole was over seven miles deep (12,262 meters), making it by far the deepest hole ever drilled by humankind. Many of the samples plucked from the borehole were dated at 2.7 billion years old.

Says Dr Teagle: 'All of the rocks from the crust at one stage were produced by partially melting the mantle. So, actually, it's the most important chemical reservoir of our planet. So if we really want to understand how our Earth has evolved over its history since its formation, then we need to have a very precise view of the chemical composition of the mantle.'