Drill tower of the main borehole at Bortum-Erbendorf, Germany. Image Source: W.J.Pilsak/wikimedia commons via Discover.
Since the 1980s, crews have drilled near Windischeschenbach in northern Bavaria in Germany; they made an exploratory hole almost six miles deep (29,859 feet). They chose a spot which once lay on the fault line of an ancient continent. From Discover Magazine blog:
Drilling of the KTB borehole began in the late 1980s in a region of southern Germany called the Zone von Erbendorf-Vohenstrauß—the line where two ancient landmasses once merged to become the supercontinent Pangaea. The geology was bound to be interesting here, but even geologists were surprised by what they saw ... shifting seismic plates, boiling hydrogen, and temperatures reaching 600 degrees Fahrenheit … . The deep-drilling experiment yielded huge surprises about the structure of the earth, including maps of rock temperature, new information about seismic pressure, and beautiful models that show layers of rock wrapped around each other like ribbons.
The Russians' Kola Superdeep Borehole cap, welded shut, August 2012. Image Source: Wiki.
The German KTB borehole is the deepest artificial accessible point in the world. There are deeper, inaccessible oil wells. The natural Mariana Trench is slightly deeper than the German borehole. The Trench was explored by Canadian film director James Cameron in an exploratory vessel, Deepsea Challenger, in 2012. Incidentally, when Cameron reached the bottom of the ocean in this dangerous and daring exercise, his phone rang. His wife called to check up on him. He later joked that once a man gets married, he might think he's free when he goes off to explore the limits of the world, but he can never escape his wife. L3 provided the communication system for this extraordinary phone call.
In the case of the German borehole, we have a different audio sample. Drilling at the German KTB borehole stopped because, as in the Russian case, the funding ran out. Before the project ended, Dutch Gen Y artist Lotte Geeven recorded sounds at the base of the borehole, which you can hear below.
Audio Source: Lotte Geeven via Gizmodo via Discover Magazine.
You can see more about the story as it was originally reported at Gizmodo, which includes riveting seismic sound samples from earthquakes:
These moans aren't all that unique from the sounds beneath the boreholes, but they feel different to our human ears. Geoff Manaugh describes them as a "melancholic howl," while [sound artist Mark] Bain ... says they are "a bell-like alarm denoting histories in the making." Either way, we have our own ideas about what these cracks and grumbles articulate about the secret world below our feet.
See all my posts on Millennial Extremes.