How deep underground is that?
Everything humans have dug is a scratch. The deepest hole ever drilled reaches 0.2% of the way to the centre of the Earth.
95% of a deepest metro station
100 m is deeper than 3 of the 8 references on this page.
Reference figures are measurements and are rounded; the unit conversion behind them is exact.
| Reference | Size | Yours ÷ theirs | Note |
|---|---|---|---|
| house basement | 2.5 m | 40× | |
| deepest London Underground platform | 58.5 m | 1.71× | Hampstead |
| Channel Tunnel below the seabed | 75 m | 1.33× | |
| deepest metro station | 106 m | 0.948× | Arsenalna, Kyiv |
| deepest cave | 2,212 m | 1/22.1 | Veryovkina, Georgia |
| Mponeng gold mine | 4,000 m | 1/40 | The deepest mine on Earth |
| Mariana Trench | 10,935 m | 1/109 | For comparison — the deepest ocean |
| Kola Superdeep Borehole | 12,262 m | 1/123 | The deepest hole ever drilled |
Worth knowing
- The Kola Superdeep Borehole reached 12 262 m after 20 years and stopped because the rock was 180 °C and behaving like plastic.
- Miners at Mponeng work in rock at 66 °C, cooled with slurry ice pumped down from the surface.
Frequently asked
What is the deepest hole ever dug?
The Kola Superdeep Borehole in Russia, at 12 262 m. It is only 23 cm across at the bottom, and it penetrated about a third of the way through the continental crust.
Why does it get hotter underground?
The geothermal gradient — around 25 °C per kilometre in continental crust — comes from radioactive decay in the rock plus heat still leaking from the Earth’s formation.