Inner core

1936

Inner core

The book of science

Tom Sharp

Inge Lehmann geophysics

Inner core

Composition

Myths of the interior

The deepest gold mine in South Africa is only 11,762 feet (2.23 miles) deep. The Kola Superdeep Borehole SG-3 is the deepest hole at 40,230 feet (7.62 miles). Earth’s crust varies in depth, from 3 miles under oceans to 60 miles under continents.

See also in The book of science:

Readings on wikipedia: