On Russia’s Kola Peninsula, near Norway, geologists have been drilling a well since 1970. Now at over 40,000 feet deep, it is the deepest hole in the Earth. The next deepest hole is the Bertha Rogers well in Oklahoma, a gas well for which drilling stopped at 32,000 feet when molten sulfur was reached.
The Kola well is being dug to study Earth’s crust. It now goes about one third through the crust of the Baltic continental shield, penetrating to rocks 2.7 billion years old.
Scientists noted a change in seismic velocities at the bottom of a layer of metamorphic rock — formed by a change in its composition, the effects of intense heat and pressure — that extends from three to six miles down.
It had been thoroughly fractured and was saturated with water. No one expected to find water at that depths.