Inge Lehmann: Discoverer of the Earth's Inner Core 2/4/17, 524 PM Log In | Register Select Language​▼ Search Keywords or Topics GO SHARE: (http://www.facebook.com/sharer.php?u=http://www.amnh.org/explore/resource-collections/earth-inside-and-out/inge-lehmann-discoverer-of- the-earth-s-inner-core) Explore(http://twitter.com/intent/tweet? Inge Lehmann: Discoverer of the Earth's Inner text=Inge%20Lehmann%3A%20Discoverer%20of%20the%20Earth%27s%20Inner%20Core&url=http://www.amnh.org/explore/resource- collections/earth-inside-and-out/inge-lehmann-discoverer-of-the-earth-s-inner-core)Science Topics Core Kids Guide to the How can we find out what’s happening deep inside the Earth? Collect Museum The temperatures are too hot, pressures too extreme, and distances too vast to be explored by conventional probes. So Resource Collections scientists rely on seismic waves—shock waves generated by earthquakes and explosions that travel through Earth and Biodiversity Crisis across its surface—to reveal the structure of the interior of the Cosmic Horizons planet. Thousands of earthquakes occur every year, and each Earth Inside and one provides a fleeting glimpse of the Earth’s interior. Seismic Out signals consist of several kinds of waves. Those important for understanding the Earth’s interior are P-waves, (primary, or A Conversation compressional waves), and S-waves (secondary, or shear with Jacques waves), which travel through solid and liquid material in Malavieille different ways. Forecasting Earthquakes Using Paleoseismology The seismograph, which detects and records the movement of Dr. Inge Lehmann (1888-1993), seismic waves, was invented in 1880. By the end of that Looking For Life In discoverer of the Earth's inner decade seismic stations were in place all over the world. At the Antarctica core. Photo courtesy of B.A. Bolt. time, geophysicists believed Earth to be made up of a liquid Mapping Hot core surrounded by a solid mantle, itself surrounded by a Springs on the crust, all Deep Ocean Floor separated by abrupt density changes in the Mapping Mt. Earth called “discontinuities.” Rainier Retrieving a In 1929 a large earthquake occurred near New Stromatolite from Zealand. Danish seismologist Inge Lehmann the Sahara Desert “the only Danish seismologist,” as she once Studying Tree Rings referred to herself—studied the shock waves to Learn About and was puzzled by what she saw. A few P- Global Climate waves, which should have been deflected by Ultra-High-Pressure the core, were in fact recorded at seismic Experimentalist stations. Lehmann theorized that these waves Who Studies the had traveled some distance into the core and Deep Earth then bounced off some kind of boundary. Her The seismic waves called S-waves do not travel Zircon Chronology: interpretation of this data was the foundation through liquid. We know that the outer core is Dating the Oldest of a 1936 paper in which she theorized that liquid because of the shadow it casts in S-waves. Material on Earth Earth’s center consisted of two parts: a solid Illustrations © American Museum of Natural History Earth: Inside and inner core surrounded by a liquid outer core, Out Glossary separated by what has come to be called the Lehmann Discontinuity. Lehmann’s hypothesis Harry Hess: One of was confirmed in 1970 when more sensitive seismographs detected waves deflecting off this the Discoverers of solid core. Seafloor Spreading Arthur Holmes: Harnessing the Born in Denmark in 1888, Lehmann was a Mechanics of pioneer among women and scientists. Her Mantle Convection early education was at a progressive school to the Theory of where boys and girls were treated exactly http://www.amnh.org/explore/resource-collections/earth-inside-and-out/inge-lehmann-discoverer-of-the-earth-s-inner-core/ Page 1 of 3 Inge Lehmann: Discoverer of the Earth's Inner Core 2/4/17, 524 PM Continental Drift alike. This was a sharp contrast to the James Hutton: The mathematical and scientific community she Founder of Modern later encountered, about which she once Geology protested to her nephew, Niles Groes, “You Inge Lehmann: should know how many incompetent men I had Discoverer of the to compete with—in vain.” Groes recalls, “I Earth's Inner Core remember Inge one Sunday in her beloved garden…with a big table filled with cardboard Milutin oatmeal boxes. In the boxes were cardboard Milankovitch: cards with information on earthquakes…all over Seeking the Cause of the Ice Ages the world. This was before computer processing was available, but the system was SunScapes: Our the same. With her cardboard cards and her Magnetic Star The seismic waves called P-waves pass through the oatmeal boxes, Inge registered the velocity of Online Field core and are detected on the far side of the Earth. propagation of the earthquakes to all parts of Indirect signals received in the P-wave shadow zone the globe. By means of this information, she Journals suggest there is a solid inner core deflecting some waves. Illustrations © American Museum of Natural deduced new theories of the inner parts of the Seminars on History Earth.” Science Student Work from A critical and independent thinker, Lehmann LeFrak Class of the subsequently established herself as an Month Contest authority on the structure of the upper mantle. Winners She conducted extensive research in other Macmillan/McGraw countries, benefiting from an increased global Hill Science 2008 interest in seismology for the surveillance of clandestine nuclear explosions. When MacMillan McGraw- Lehmann received the William Bowie medal in Hill Science 2005 1971, the highest honor of the American Geophysical Union, she was described as “the 2013 Master of Arts master of a black art for which no amount of in Teaching computerizing is likely to be a complete Graduates substitute.” Lehmann lived to be 105. Cut away showing the four main layers of Earth: 2013 Richard Gilder solid inner core, liquid outer core, mantle, and crust. 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