Humans have traveled over 225,000 miles to the moon, but still haven’t seen 3 miles beneath our own feet.
It’s a modern day Journey to the Center of the Earth — minus the sea-monsters and menacing villains! Getting beneath Earth’s crust to its denser underlying mantle is one of the biggest goals in the field of geology, and humans have been trying to do it since the 1960s. All who have attempted the task have failed, and unfortunately, the same is true for the latest expedition. But they are going to try again!
The crust-mantle boundary is marked by a feature known as the Mohorovičić discontinuity, or ‘Moho’, where seismic waves change velocity. However, at the Atlantis Bank, the mantle is believed to rise as much as 1.6 miles (2.5 kilometers) above the Moho, making it much easier to reach.
The Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES) expedition left on November 30, 2015, to drill to the Earth’s mantle in the Atlantis Bank of the Indian Ocean, and it concluded yesterday (January 30).
Henry Dick, a geophysicist at the Woods Hole Oceanographic Institution in Massachusetts and co-leader of the expedition, and his colleagues, targeted the Indian Ocean because much smaller quantities of lava feed the sea floor there, so there is less hard rock to drill through.
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The plan of the expedition was to drill 1,500 meters into the Atlantis Bank, located just 700 meters (2,300 feet) below the ocean’s surface. They managed to get an amazing 700 meters deep, and collected gabbros rocks that form when slow-cooling magma is trapped under Earth’s surface.
Collecting these rocks will help scientists understand the processes that create mid-ocean ridge basalts. Not only that, “[t]he JR takes core samples and measurements from under the ocean floor, giving scientists a glimpse into Earth’s development and also a scientific means of measuring climate and environmental change throughout a significant part of our planet’s history,” says the JOIDES Facebook page.
Dick is confident the team will reach their preliminary goal of 1,500 metres, because he has done it before. In 1997, he led an expedition to Atlantis Bank that got that deep before disaster struck: the pipe broke off due to high winds, corkscrewed down inside the hole and plugged it. “We’re going to make sure that doesn’t happen this time,” he said to Nature.
Other expeditions have come close before. For example, between 2002 and 2011, four holes were drilled in the eastern Pacific which reached fine-grained, brittle rock believed to be cooled magna sitting just above the Moho. However, the drills were not capable of getting through these hard layers.
A second mission is now in the works, and the hope is that humans will reach the mantle within five years! Reaching these deep-Earth frontiers “is one of the great scientific endeavours of the century,” said Dick.
