For the first time ever, scientists drill into the Earth’s rocky mantle

They dug at a special “tectonic window” in the North Atlantic where the rocks of the mantle have been pushed close to the surface.
Loukia Papadopoulos
An illustration of Earth's mantle.jpg
An illustration of Earth's mantle.


Scientists have finally drilled into Earth's mantle by going nearly a mile beneath the ocean floor at an underwater mountain in the middle of the Atlantic Ocean.

This is according to a report by the Washington Post published on Tuesday.

The event was a record-breaking achievement by an ocean drilling vessel called the JOIDES Resolution.

It should be noted that the scientists did not technically drill into the mantle, and the hole isn’t the deepest ever drilled beneath the ocean floor. Instead, researchers decided to dig at a particular “tectonic window” in the North Atlantic where the rocks of the mantle have been pushed close to the surface.

Andrew McCaig, the expedition’s co-chief scientist, said he was surprised that the drill yielded tube after tube of dark rock.

“It just kept going deeper, deeper and deeper. Then everyone in the science party said, ‘Hey, this is what we wanted all along. Since 1960, we wanted to get a hole this deep in mantle rock,’” McCaig told the Washington Post.

The team managed to get rock samples from as deep as 4,157 feet below the seafloor.

“We’ve achieved an ambition that’s been feeding the science community for many decades,” McCaig said.

Examining the new rocks

Now, scientists on land can’t wait to study the new rocks.

“We are just to the moon with excitement about what they’ve got — an amazing section of rocks,” said Andrew Fisher, a hydrogeologist at the University of California at Santa Cruz, who advises a graduate student who is aboard the ship and has been monitoring their progress remotely.

“Think of the crust in the way that you have a beautifully iced cake, but what you want is the cake, not the icing,” said Jessica Warren, a professor of Earth sciences at the University of Delaware who has also been monitoring the project’s progress remotely.

“If we want to understand the Earth as a whole, there’s a huge, huge amount of rock below that.”

Initial reports indicated that newly-extracted rock cores are dominated by peridotite, the most common type of rock in the upper mantle. However, the samples have been changed by their exposure to seawater, leading scientists to question how to interpret the findings.

One question arises whether the boundary between mantle and crust is a sharp boundary or more of a gradual transition.

“It’s a bit of a hash, but that’s maybe what the lower crust is,” Fisher told the Washington Post. “This is really unusual — more than a kilometer of highly altered, lower crustal and/or upper mantle rock. I’d say it’s a mix.”

The researchers involved with the dig are excited by the hope that the deepest samples will yield even “fresher” rock, less altered by other processes and closer to what the mantle consists of.