The Deepest Hole on Earth
The deepest hole in the world is on the Kola peninsula of Russia near the Norwegian border. This hole is being drilled for scientific study purposes and is currently over 12,200 meters deep. The project attempted to drill as deep as possible into the Earth's crust. Drilling began on 24 May 1970 using the Uralmash-4E, and later the Uralmash-15000 series drilling rig.
The Kola borehole penetrated about a third of the way through the Baltic continental crust, estimated to be around 35 kilometres (22 mi) deep, reaching rocks of Archaean age (greater than 2.5 billion years old) at the bottom. In 1926, Harold Jeffreys hypothesized that a transition zone within the crust, identifiable on seismic records as a “jump” in seismic velocity, could be attributed to a change in rock type from granite to a denser basalt. Then deepest hole in the world being drilled at the Kola well has now penetrated about halfway through the crust of the Baltic continental shield, exposing rocks 2.7 billion years old at the bottom. One of the more fascinating scientific findings to emerge from this well is that the change in the seismic velocities was not found at a boundary marking but it was at the bottom of a layer of metamorphic rock that extended from about 3.5 to about 9.8 km beneath the surface. Free water should not be found at these depths. This could only mean that water which had originally been a part of the chemical composition of the rock minerals themselves had been forced out and prevented from rising by a cap of impermeable rock.
This discovery has an great impact on geophysical sciences and there is a potential economic impact. This water is very highly mineralized, and is a primary concentrating agent for most ore deposits. The technology for mining at these depths is not yet available. Their chief innovation was that, instead of turning the drill bit by rotating the stem, in the Kola well the bit alone was turned by the flow of drilling mud.
As drilling continues at the deepest hole in the world many scientists are hoping for additional discoveries and a greater understanding of the inner workings and makeup of our planet.