Lehmann, Inge

[lay man] (1888–1993) Danish seismologist: discovered solid inner core within Earth’s outer liquid core.

Inge Lehmann studied mathematics in Copenhagen and in Cambridge, and afterwards worked in insurance until she was 30, before returning to study science in Copenhagen. From 1928 she headed seismological work at the Danish Geodetic Institute, dealing with seismic data recorded from all parts of Europe. At that time the Earth was believed to consist simply of a liquid core, shown to exist by , surrounded by the mantle and then the crust. But in 1936 Lehmann observed that compressional P waves travelling through the Earth’s core from an earthquake undergo a marked increase in velocity at a depth of about 5150 km. She argued from this that there is a solid inner core within the liquid core, extending about 1200 km from the Earth’s centre. It is believed that this inner core consists of solid iron and nickel, the very high pressure making the metal solid despite its high temperature.