How much do we know about what’s deep down under our feet?
http://www.bbc.co.uk/reel/video/p09klm1x/the-cold-war-race-to-the-centre-of-the-earth
How much do we know about what’s deep down under our feet?
http://www.bbc.co.uk/reel/video/p09klm1x/the-cold-war-race-to-the-centre-of-the-earth