How Deep Is the Deepest Hole in the World?

The deepest hole in the world goes down 12,262 meters, about 7.6 miles. It sits on the Kola Peninsula in northern Russia, far above the Arctic Circle. Soviet scientists drilled there for 22 years. Then they had to give up because the rock got too hot. Sounds deep? It is. The hole reaches farther down than Mount Everest is tall. And yet humanity barely scratched the surface: the center of the Earth is still more than 6,000 kilometers away. We'll show you how deep we really got and what the drill brought up along the way.

12,262 meters: deeper than the Mariana Trench

The Kola Superdeep Borehole, known as SG-3, reached a depth of 12,262 meters (40,230 feet) in 1989. It is still the deepest hole humans have ever drilled. For context: the Mariana Trench, the deepest spot in the ocean, goes down about 10,900 meters. The borehole reaches more than a kilometer deeper than that.

The tallest mountain loses this contest too. Mount Everest stands 8,849 meters tall. Flip it upside down into the hole and there would still be more than 3 kilometers of room below its peak. Quick math: the hole is also about 6 times deeper than the Grand Canyon. And it is surprisingly narrow. At the bottom it measures only about 23 centimeters (9 inches) across, roughly the width of a dinner plate. No human has ever been down there, only the drill bit.

Why the Soviets drilled for 22 years

Drilling started in 1970 on the Kola Peninsula in northwestern Russia, near the town of Zapolyarny. The goal was pure science: the Soviet Union wanted to know what the Earth's crust looks like deep down. There was also a race with the United States, similar to the space race. The Americans had already canceled their own deep drilling project in 1966. The Soviets kept going, year after year, with custom-built rigs that existed nowhere else. In 1989, the drill hit its record depth of 12,262 meters. The plan was to reach 15,000 meters. That never happened.

Why drilling stopped at 12 kilometers

The enemy was not technology. It was heat. Scientists expected around 100 °C (212 °F) at 12 kilometers. They measured about 180 °C (356 °F). At those temperatures, rock softens and starts to behave almost like modeling clay. The hole began closing itself whenever the drill was pulled out. In 1992, the team stopped drilling for good. Shortly after, the Soviet Union collapsed, and the funding disappeared with it. The drill tower is gone today. The deepest hole in the world now sits under a rusty metal cap, welded shut.

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What scientists found down there

The borehole delivered some of the biggest surprises in geology. At around 6 kilometers down, researchers found microscopic fossils of marine plankton. Estimates suggest they are about 2 billion years old. They also hit liquid water at depths where textbooks said there should be none. And according to the people involved, the drilling mud practically bubbled with hydrogen gas. One thing they did not find: hell. A famous internet legend claims that microphones recorded screams deep in the hole. The story is made up. The audio apparently came from a horror movie.

How deep can we drill today?

Kola still holds the record for the deepest vertical hole. There are longer boreholes, like the Z-44 oil well off Sakhalin Island in Russia, which measures 12,376 meters in total length. But most of that runs sideways under the seabed. Straight down, nobody has beaten the Soviets. Germany drilled a superdeep hole of its own: the KTB borehole in Bavaria stopped at 9,101 meters in 1994 and is still used for research today. For context: continental crust is about 35 kilometers thick on average. Even the record-setting Kola borehole only made it through roughly a third of the crust. The Earth's mantle remains untouched.

Remember one number: 12,262 meters. Humanity never got deeper than that. If records like this hook you, read how deep the ocean really is or check out the tallest structures in human history. And if you'd rather guess than read: our technology quiz questions are waiting.