The Russians dug a nine-inch diameter hole 7.5 miles under the ground just to see what was there-until the Earth’s crust started melting their equipment.

One of the weirdest aspects of the Cold War between the United States and the USSR was to see who could dig the deepest hole into the Earth’s crust. The Americans succeeded only in digging 601 feet (183 meters) below the sea’s floor through 11,700 feet (3566 meters) of water as part of Project Mohole off the Pacific coast of Mexico. The Russians, on the other hand, spent three decades digging deeper into the crust, eventually reaching 40,230 feet (12,262 meters). The Kola Superdeep Borehole was halted at that level, short of the anticipated goal of 49,000 feet because the drill bits started malfunctioning at the unexpectedly high temperature of 356° F (180° C).

Did You Know?

  1. The Kola Superdeep Borehole sits in the Pechengsky District of Russia and was started on May 24 1970.
  2. The borehole actually is a series of holes, all branching off from a central hole.
  3. The deepest portion of the hole, while only nine inches in diameter, is 40,230 feet (12,262 meters) deep.
  4. The hole remains the deepest borehole, despite the 40,502-foot-long (12,345 meter) Skhalin-I Odupto OP-11 well, dug in Russia in 2011.
  5. Scientists were stunned by the discovery of fossilized plankton, single-celled organisms two billion years old.
  6. They were also baffled by the lack of transition between granite to basalt, called the “Conrad discontinuity.”
  7. Another surprise: water! It’s believed to come from tremendous pressure forcing out hydrogen and oxygen atoms.
  8. The Kola Superdeep Borehole was capped and abandoned in 2008, its top marked with an average-looking manhole.
  9. Next on the horizon: Japan’s attempt to dig even deeper, aiming for the Earth’s mantle, 6 miles (10 kilometers) under the sea floor.
  10. Drilling is expected to start by 2030 but the location of the project is undetermined.