Kola Superdeep Borehole, Russia, USSR -- Scientific Drilling Project of the Soviet Union

😲 #Kola #Superdeep #Borehole 😱 The Deepest Hole ever Drilled, reaching a depth of 40,226 feet (7.62 miles)... for scientific research w/ some unexpected discoveries, incl'ding one huge deposit of Hydrogen - So massive that the mud was boiling out!