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Kola Superdeep borehole

Kola Peninsula

The Kola Superdeep Borehole reached about 12 km into Earth’s crust. Comparing that depth with Earth’s layers shows why scientists rely on seismic evidence to investigate the interior.

Aerial view of abandoned buildings at the Kola Superdeep Borehole site in Russia in 2020.
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Kola Superdeep Borehole site, 2020. The deepest borehole reached 12.262 km within continental crust; it did not enter the mantle.
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Location: 69.40°, 30.60°

Drilling at Kola sampled only a small fraction of the continental crust, despite reaching a depth of roughly 12 km. The mantle and core lie far beyond that direct reach. Rock samples answer valuable local questions but cannot provide a complete section through the planet.

Open the Earth-interior model and compare the borehole depth with the crust and mantle. Discuss how seismic waves, gravity and other evidence constrain regions that cannot be directly visited or drilled.

Open this state in the lab

Exam-style question

Why is the Kola borehole not evidence for the composition of the outer core?

Teacher hint: Compare roughly 12 km of drilling with about 2,900 km to the core–mantle boundary, and explain the role of indirect seismic evidence.

Process labs

Earth’s interior

Sources

  • BGS / USGS interior summaries