As this picture (in the same scale as the big graphic in my previous blog) shows though, the borehole was still a long way from reaching the mantle when work was stopped in the early 1990s. However, scientists are still working on a range of deeply boring projects (sorry scientists), so hopefully one day soon we’ll get literally to the bottom of things!

Deep deep holeunderwater

Taking up the mantle Later in the twentieth century, a range of other attempts were made to get close to the Moho disconuity. Definitely the most impressive, in my humble opinion, was the Soviet Union’s Kola Superdeep Borehole. The deepest part of this borehole was drilled to an amazing 12,262 metres below the surface. That’s further than the height from the top of Mount Everest to the bottom of the nearest sea!

Deep deep holeon earth

In that piece, I pointed out that most of our knowledge of the inner parts of our planet comes from indirect observation, as no-one has managed to drill right through the Earth. But surely we’ve tried to right? Turns out we have. But even the best efforts haven’t managed to drill through the crust – the very top layer – to get to the mantle below. However, a few scientists have given it a pretty good go.

One of the earliest attempts to reach the mantle layer – called ‘Project Mohole’ – ran from the late 1950s into the early to mid ’60s. They were trying to reach the ‘Moho discontinuity’ where the crust meets the mantle – and named after our old unpronounceable Croatian pal Andrija Mohorovičić. This project attempted to bore a hole through the Earth’s crust in the deep sea off Mexico (as the crust is much thinner under sea than on land). Unfortunately, funding to this project was cut before the scientists had managed to bore a hole deeper than couple of hundred metres below the seabed! (although apparently some useful discoveries were made in doing so)

FIND OUT MORE: If you want to know more about the Kola Superdeep Borehole, including what it looks like these days, check out this post from IFL Science and this video from SciShow