Inge Lehmann

This Danish scientist worked out that Earth’s inner core is solid and not liquid.

The GEOLOGIST who studied earthquakes and discovered Earth’s deepest secretDid you know? Lehmann attended Denmark’s first co-educational school, where both boys and girls studied the same subjects.

Beneath the surface

Inge Lehmann’s career in SEISMOLOGY – the study of earthquakes and the seismic waves they produce – began in 1925 when she became responsible for analyzing data from seismic observatories. Seismic waves travel at varying speeds through different layers of Earth, revealing clues about Earth’s inner mysteries.

Who came before…

The liquid outer core is mainly molten iron and nickel. The inner core is a ball of solid iron and nickel.

English seismologist John Milne designed one of the first seismographs in 1880. He analyzed earthquake data from his Isle of Wight observatory. In 1897, British geologist

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identified three different types of seismic waves. Studying the speed of these waves, he concluded that Earth must have a central core.

At the time, scientists believed Earth consisted of a liquid core surrounded by a solid mantle. In 1929, a large EARTHQUAKE in New Zealand sent shockwaves around the world. Using basic technology, Lehmann analyzed the data and noticed that some seismic waves appeared to be bouncing off a boundary within Earth’s core. In 1936, she published her theory that Earth’s centre consists of a solid inner core surrounded by a liquid outer core.

By the way… Without a computer, I recorded my data on slips of cardboard and stored them in old cereal boxes.

Lehmann was the first woman to receive the William Bowie Medal.

Leading expert

Lehmann established herself as an expert on Earth’s upper mantle. In later years, she discovered another boundary, about 220 km (137 miles) below Earth’s surface, now known as the LEHMANN DISCONTINUITY. During her lifetime, Lehmann received many awards, including the American Geophysical Union’s William Bowie Medal in 1971.

What came after…

In 1935, seismologists Charles Richter and Beno Gutenberg

developed a system for measuring earthquakes, using a scale of 0–10. The higher the number, the stronger the earthquake. A seismograph is used for recording the earthquake’s seismic waves. In 2017, with the help of the powerful Titan supercomputer and seismic data generated by 253 earthquakes, Princeton

University researchers created a detailed 3D

How she changed the world

Inge Lehmann’s discovery helped to redefine how our planet was studied. She was also a pioneer of equal rights at a time when there were few opportunities for female scientists.