Journey To the Mantle of the Earth By 2020
An anonymous reader writes "A half-century after the first attempt to drill through the ocean crust into the Earth's mantle, a new campaign armed with improved technology is underway that could reach the mantle by the end of the decade, researchers say."
What would tend to happen is that as they drill the hole, lava starts climbing up the shaft and cooling again into solid rock. Even once they are all the way through, the lava will still quickly cool into rock as it comes onto the surface.
Ultimately, it would amount to becoming a man-made volcano... one that would probably take several centuries before it was of any significant size, and that's assuming that it remains active for that amount of time.
File under 'M' for 'Manic ranting'