the deepest well

On Russia's Kola Peninsula, near the Norwegian border at about the same latitude as Prudhoe Bay, the Soviets have been drilling a well since 1970. In 1985 it's depth reached 40,000 feet, making it the deepest hole on earth (the previous record holder was the Bertha Rogers well in Oklahoma--a gas well stopped at 32,000 feet when it struck molten sulfur).

It is not oil or gas that is being sought with the Kola well, but an understanding of the nature of the earth's crust.

That's 7.57 miles down showing how thin is the earth's crust.