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Beno Gutenberg

Right to the Core

On June 4, 1889, geophysicist and mathematician Beno Gutenberg was born and made the study of Earth’s interior his life’s work. He was the first to determine the radius of Earth’s core.

Perhaps the most important information geologists gather about Earth’s interior comes from earthquake vibrations radiating outward in seismic waves. Primary and secondary waves are called P-waves and S-waves. Each type of seismic wave changes as it travels though different materials in the Earth so scientists analyze seismic data to work out the composition of Earth’s layers. Seismic waves travel faster through denser material and also display a change in speed and shape.

Earth’s crust, the thin shell of rock that covers Earth, contains all the mountains, valleys, oceans, and plains that make up the surface of the planet. The crust sits on a mantle of partially melted material over 2600 km (1600 mi) thick. The continual motion of the mantle densities creates stress above it causing the slabs or plates of crust to move toward, away, or under each other. Below the mantle is Earth’s core, over 3600 km (2200 mi) thick, consisting of a solid inner core suspended in a molten outer core whose iron-rich fluids and currents are believed to be responsible for Earth’s magnetic field.

At a depth of 2900 km (1800 mi), Gutenberg found an abrupt change in the seismic wave patterns. At this level, the S-waves disappear completely, indicating that the material below is liquid. This seismic transition zone separating the mantle from the outer core, or core-mantle boundary, is known today as the Gutenberg Discontinuity. Accompanying this change is an abrupt temperature increase of 700°C (1,300°F). At about a depth of 5,150 km (3,200 mi), the remaining seismic waves speed up to indicate that the inner core is solid.

Professor Gutenberg helped develop seismology into an international science of earthquake study and detection at the California Institute of Technology and served as the Director, Seismological Laboratory from 1946 – 1957. To honour the scientific achievements of this pioneering seismologist, the European Geosciences Union awards the Beno Gutenberg Medal to an individual as recognition of outstanding contribution to Seismology.

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