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Drilling into Earth’s Interior is no easy task. The Kola Superdeep Borehole is one of the projects that tried to do it.

STEM Explained The Deepest Hole in the World Earth Science Earth Materials/Processes facebook X/Twitsubjects-bubblester LinkedIn Pinterest Print / Impression Abandoned superstructure of Kola Superdeep borehole (Andre Belozeroff, Wikimedia Commons) facebook X/Twitsubjects-bubblester LinkedIn Pinterest Print / Impression Have you ever thought about what it takes to drill to the centre of the Earth? If you think it sounds difficult, you’re right! Not only has no one ever drilled to the centre of the Earth, no one has ever even managed to drill through the Earth’s crust. In fact, we know more about outer space than we do about what’s under the Earth’s surface! We know that Earth has layers. The Earth is made up of a crust, mantle, and core. Both the mantle and core have inner and outer components. Temperatures inside the Earth range (source of temperatures) (© 2019 Let’s Talk Science using an image by Mats Halldin Vectorization: Chabacano [CC BY-SA 3.0 via Wikimedia Commons). Illustration - Text Version Temperatures in the inner core are greater than 6 000 degrees Celsius. the temperature in the outer core ranges from 3 800 to 6 000 degrees Celsius. The temperature of the mantle ranges from 2 000 to 3 000 degrees Celsius and the temperature of the crust is less then 2 000 degrees Celsius. The Earth’s crust is the thinnest layer. It ranges from about 5 to 70 kilometers thick. On average it’s about 40 kilometers thick. Consider 40 kilometers. That’s about 3 times the distance of the Confederation Bridge that connects Prince Edward Island and New Brunswick! Did you know? If the Earth were an apple, the crust would be equivalent to its skin! Has anyone ever tried to dig through the Earth’s crust? As a matter of fact, yes. During the 1970s, the Soviets gave it their best shot with the Kola Superdeep Borehole project on the Kola Peninsula. The project quietly took off during the Space Race between the Soviets and the Americans. The main goal was to find … well, whatever they could. They managed to dig to a depth of 12 262 metres. That’s just over 12 kilometres. Then, in 1992, the project came to a halt. But this depth is deeper than the deepest point in the ocean: the Mariana Trench, which is approximately 11 000 metres (or 11 km) deep. The Deepest Hole in the World (2014) by SciShow (4:00 min.). How did they do it? Boreholes are typically used in the oil and gas industry. But the Kola Superdeep Borehole was used in search of something else: information about the Earth’s crust. To dig the Kola Superdeep Borehole, scientists invented a drill in which only the bit (the tip) rotated. They also had to use a lubricant to help the drilling process.The lubricant they used was pressurized drilling mud. Did you know? Although the Kola Superdeep Borehole went extremely deep under the Earth, it was only 23 centimetres (about 9 inches) wide! Eventually, the project ended.The temperature of the rock at 12 kilometres deep was much higher than scientists thought it would be. They had prepared for temperatures close to 100 degrees Cecius. But the rocks were much closer to 180 degrees Celsius! They weren’t prepared for this extreme heat, so they had to stop digging. The borehole was capped. The cap on the Kola Superdeep Borehole (welded shut) taken in August, 2012 (Source: Rakot13 [CC BY-SA 3.0] via Wikimedia Commons). What did they discover? The Kola Superdeep Borehole led to a number of fascinating discoveries. For example, there is a lot of water underground! This discovery was one of the most important. Scientists believe that this water is actually trapped in the rocks that make up the Earth’s mantle and parts of the crust. They think it is trapped in the form of hydrogen and oxygen atoms. The drilling process released some of these trapped gas atoms, producing water. Scientists also discovered microscopic plankton fossils at around 6.7 kilometers below the Earth’s surface! Twenty-four different species of ancient microplankton were catalogued during the project. Did you know? Rumours spread that the Kola Superdeep Borehole project ended because drillers hit a very hot, hollow cavity and heard the sound of “screams” escaping. Have there been other super deep holes dug since then? Several superdeep drilling projects followed the footsteps of the Kola Superdeep Borehole project. In the late 1980s, the German Continental Deep Drilling Program attempted to drill their own borehole. That project ended because of high temperatures, too. At depths of 9 100 metres, they reached temperatures close to 260 degrees Celsius! Some projects have also attempted drilling through the Earth’s crust underwater. The Japanese drillship Chikyu is the most notable example. The ship is designed to operate in waters up to 2 500 metres deep. It is designed to drill a further 7 000 metres into the Earth’s crust. Its most recent expedition took place in 2009. JAMSTEC (Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technolo...