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Kola Superdeep borehole

Kola Peninsula

The deepest hole in rock, about 12 km. Continental crust goes on for another 20 km. The mantle was never reached.

Scientific cutaway of Earth’s crust, mantle and core. — The deepest borehole still sat in crust. Waves, not a well, read the core.TerraLens classroom drawing after USGS layer radii

Locator · OpenStreetMap / OpenFreeMap · 69.40°, 30.60°

We know the outer core is liquid because of S-wave shadows, not because someone brought back a sample. Kola is the humility exhibit: the crust is a skin, drilling is hard, temperature and rock strength win.

The interior lab’s explode and slice, then P and S waves, are how we actually know. Kola is how we do not.

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: 12 km vs ~2900 km to the core-mantle boundary. Seismology, not drilling, is the tool.

Process labs

Earth’s interior

Sources

BGS / USGS interior summaries