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China is drilling some of the world’s deepest holes in hunt for ... - CNN
Deepest blue hole in the world discovered, with hidden caves and ...
Why Did the Russians Seal Up the Deepest Hole in the World?
Researchers found the planet's deepest under-ocean sinkhole - CBS News
Scientists Drill Deeper Into Earth's Mantle Than Ever Before, …
Kola Superdeep Borehole - Wikipedia
The deepest hole we have ever dug - BBC
Scientists Pinpoint World's Deepest Underwater Sinkhole
China Is Drilling a 10,000-Meter-Deep Hole Into the Earth
How Deep Is the Deepest Hole in the World? - Scientific American