That's Deep

Kola Superdeep Borehole

This is the only picture you get... Because it's a hole in the ground.

Started under the Soviet Union, on May 24, 1970. By 1989, it was the deepest hole ever drilled, and the “deepest artificial point on Earth” at 40,230 ft.

That's over 7 miles into the Earth.

Drilled in stages, the well was initially supposed to reach the target depth of 49,000 feet. However, by 1992, it was deemed unfeasible to continue past 40,230 feet after initial temperature estimates at this depth were proven incorrect. Originally estimated at 212 degrees Fahrenheit  actual temperatures at the final depth reached 356 degrees. 

A few details:

• At its current depth, the hole reaches a third of the way through the Baltic continental crust
• Rocks at the hole’s deepest point are at least 2.5 billion years old
• Now, the hole is used primarily for scientific research in such fields as:

“seismic discontinuities and the thermal regime in the Earth's crust; the physical and chemical composition of the deep crust and the transition from upper to lower crust; lithospheric geophysics; and to create and develop technologies for deep geophysical study.”

Not to be outdone, the US and Germany both set out to beat the depths of the Kola Borehole. The US project, which started out in 1957, never gained funding, and the German attempt only reached 29,859 feet because of higher than expected temperatures (which reached more than 500 degrees Fahrenheit).

The depth of the Kola Borehole has been surpassed twice, once in 2008 by an oil well in Qatar (40,318 feet deep) and again in 2011 by a Russian oil well in Bavaria (40,502 feet). However, “in terms of depth below the surface,” it still reigns supreme. It is also important to note that the Kola Borehole is different from the other mentioned here: the “deep core-drilled” method of drilling recovers the rock which is drilled though.

I like to imagine that scientists were secretly trying to reenact the plot of "Journey to the Center of the Earth" (the book, not the terrible Brenden Frasier movie from 2008).

-JJ