Plate Tectonics and People

Inge Lehmann

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"the master of a black art for which no amount of computerizing is likely to be a complete substitute" - American Geophysical Union

"The only Danish seismologist" - Inge Lehmann

Dr. Inge Lehman 13 May 1888-21 February 1993

Click on photo for more info. (4)

Birth: 1888, May 13

1907-Entered U. of Copenhagen

1910- Enterend Nenham College, Cambria

1918- Re-entered U. of Copenhagen

1920- Graduated U. of Copenhagen

1928- mag. Scient. from University of Copenhagen

1964 - Doctor of Science (Sc.D.) h.c. Columbia University, NY

Died: 1993, February 21

Inge Lehmann, Danish Seismologist

Danish Seismologist Inge Lehmann was born into a family of movers and shakers. She was raised at Osterbro, by the Lakes in Copenhagen and attended a non-traditional school that practiced gender equity. Her sister, Harriet, and she carried a legacy of influence and intellect brought from ancestral roots in Bohemia (now Czech Republic).

Inge’s interest in mathematics was initially refuted by her parents , then she passed the entrance exam with first class standing. She went on to study mathematics in physics, chemistry and astronomy at the University of Copenhagen (1907) and Nenham College, Cambria (1910). At Nenham College, Inge experienced “severe restrictions inflicted on the conduct of young girls”(3,4) and returned home from exhaustion. Inge returned to University of Copenhagen where she graduated in 1920.

Lehmann had previous experience through employment at an actuary office while on respite. Upon graduation she became assistant to professor in actuarial science at University of Copenhagen. In 1925 she was appointed assistant to Professor N.E. Norland. Norland later installed seismographic stations of which she later manned. This led her to study geodesy with thesis topic in the nature of seismology earning mag. Scient. (magister scientiarum), 1928, University of Copenhagen. At this time she was selected chief of the seismological department of Royal Danish Geodetic Institute until retirement in 1953. She travelled extensively, later earning her Doctor of Science degree in 1964 from Columbia University, NY.

Discoverer of the Earth's Inner Core

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Issues of Discontinuity in Earths Mantle and an example of how Lehmann enjoyed the spirit of a good intellectual discussion...

1926 - Byerly first acknowledges existence of 20 degrees of discontinuity.

1926 Gutenberg "proves" existence of decrease in longitudinal and transverse waves  at epicentral distance of 100-1600km.

1934 - Lehmann determines discontinuity at 250-350 km.

1936 Jeffreys determines discontinuity at 481 km. thinks it is caused by upper mantle.

1958- Gutenberg acknowledges wave velocity changes at 220km.

1962- Lehmann confirms existence of discontinuity surface at about 215km.

1964- Lehman concludes low velocity layers evident as important in mantle features.

1964- Lehmann concludes that Gutenberg and Jeffreys opinions are antithetical and therefore they both are wrong.













Other cool stuff:

*Inge published work titled “P’ ” is the shortest title in the history of seismology, maybe even in all of science!

*Lehmann once worked for an actuary company, a job which included calculating life expectancies and statistical risks for insurance companies.

*She helped to form the constitution of the European Seismological Federation.

*Lehmann was elected the first president of the European Seismological Federation (1950).

*She loved the outdoors, music, gardening and was known to visit art galleries everywhere she travelled.

*Inge Lehmann was 105 years old and nearly blind when she died.

Inge's major scientific contribution is to new understanding of the Earth's inner structure

Lehmann's discovery Lehmann's original drawing(4)

Early in Lehmann’s educational career she had studied the theory of observation intensively. Her tutelage and practice in this theory paid off while manning and maintaining seismic instrumentation from Copenhagen, Vigor and Scoresbysund stations. After studying shock waves from a large earthquake occurring near New Zealand in 1929 she noticed a difference in the seismic data.  It took a large earthquake for this data to become evident.  From what she observed Lehmann asserted that because some P-waves, which should have been deflected by the core, were of record (not deflected) then a layering in the core must be present. This layering, Lehmann theorized, is of a solid inner core, liquid outer core and is separated by some sort of boundary between the two. This boundary is known as the Lehmann Discontinuity and while for over twenty years was highly controversial it was also later confirmed (1970).

Lehmann’s Discontinuity theory broke from conventional wisdom that previously claimed the Earth’s core was liquid followed by a solid mantle and then surrounded with a crust. Each change in composition was considered to be abrupt and was called “discontinuity”. This led to the name of this discovery.  The Lehmann Discontinuity theory also led to new thinking about the Earth's composition overall.

Inge received many awards including the Tagea Brandt Award twice (1938 ,1967),  and the William Bowie Medal, 1971 which is the highest honor for the American Geophysical Union.

Inge Lehmann, 85 years of contributions

Her work ethic was intense as it had to be for a woman working as a discoverer in her time. Her most famous quote, “You should know how many incompetent men I had to compete with – in vain!”(4) speaks to her fortitude. She was a pioneer and was once found in her garden coordinating cards with seismic data written on the backs of oatmeal boxes.

Her investigation into body-wave amplitudes and travel times led to her discovery of the inner core, outer core and area of discontinuity and by 1960 more sophisticated data became available. Her keen ability for reading and coordinating seismic information was instrumental in helping the United States, which in return funded further exploration of the structure of the upper mantle. For this Lehmann used seismic data from underground nuclear explosions. By this time Lehmann was not only a source for highly accurate interpretations, she was also true to science with unbias determination which was required with nuclear politics of the time.

Lehmann's Important Publications:

  • " P' " , Union Geodesique at Geophysique Internationale, Serie A. Travaux Scientifiques 14: 87 (1936)
  • " Velocities of Longitudinal Waves in the Upper Part of the Earth's Mantle". Annales de Geophysique 15:93 (1959).
  • "The Travel Times of the Longitudinal Waves of the Logan and Blanca Atomic Explosions and Their Velocities in the Upper Mantle" , Bulletin of the Seismological Society of America 52:519 (1962)


1. A Discovery Company, Science Channel. "100 Greatest Discoveries: The Core of the Earth." (accessed January, 2011).

2. AGU and FEMA, "Seismic Sleuths." January 3, 2008. (accessed January, 2011).

3. American Museum of Natural History, "Essay Book Series, Earth Inside and Out. Edited by Edmond A. Mathez" 2000. (accessed January, 2011).

4. Bruce, Bolt. "University of California, Berkeley, Seismographic Station, Inge Lehmann." (accessed January, 2011).

5. Encyclopædia Britannica. Encyclopædia Britannica Online."Inge Lehmann." Encyclopædia Britannica, 2011. Web. 01 Feb. 2011. January, 2011)

6. Landsberg,H.E.. Advances in Geophysics, Volume 12, Volume 12. Advances in Geophysics. 12, Volume 12. London: Academic Press, 1967.

7. "Spotlight Scientist, Inge Lehmann." 1998. (accessed January, 2011).

8. Susan , Hough. "Unsung Heroine, Ruth B. Simon, Seismological Research Letters". 77. 6 (2006), 742-743, (accessed January 28, 2011).