Inge Lehmann was a Danish seismologist and geophysicist. She grew up in Copenhagen, where she attended a pedagogically progressive high school and later want on to the University of Copenhagen and the University of Cambridge to study mathematics. Lehmann received a candidatus magisterii, a master of the arts degree, in physical science and mathematics. She later returned to Denmark to work at Copenhagen University where she served as an assistant to the professor of actuarial science, J.F. Steffensen, and then began working with the geodesist Niels Norlund. While working as Norlund’s assistant, she was assigned to set up observatories of seismology in Denmark and Greenland. This work led to her receiving another degree equivalent to an MA, in geodesy. She then accepted a position as state geodesist and went to work under Norlund again at the Geodetical Institute of Denmark as head of the department of seismology. In 1936, Lehmann published a paper where she interpret P waves as reflections from an inner core: the first in the field to propose this concept. Previously, it had been thought that the earth had one molten core, and Lehmann’s findings helped show that there is a solid inner core and molten outer core. This results in P waves and seismic shifts.
Lehmann stayed at the Geodetical Institute of Denmark until 1953, when she retired and moved to the US to collaborate with Maurice Ewing and Frank Press. While working with them and investigating Earth’s crust and upper mantle, she discovered another seismic discontinuity. This discontinuity lies between 190 and 250 km and was named the Lehmann discontinuity. She wrote her last research article at age 99, and was the longest-lived woman scientist having lived past 104 years old. Throughout her life, and afterwards, she received many awards for her scientific achievements. She was also awarded honorary doctorates from Columbia University and the University of Copenhagen.
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