Beno Gutenberg
Beno Gutenberg was a German-American seismologist who used earthquake waves to locate the core–mantle boundary at about 2,900 kilometers depth.
Core–mantle boundary: The boundary between Earth’s silicate mantle and metallic outer core, about 2,900 kilometers beneath the surface. Gutenberg’s 1914 analysis placed this boundary at roughly 2,900 kilometers depth.
Seismic wave: An elastic disturbance that travels through Earth or along its surface, commonly generated by earthquakes. Gutenberg inferred deep structure from how these waves traveled through the planet.
Charles Francis Richter: An American seismologist who developed the local-magnitude scale with Beno Gutenberg in 1935. Richter and Gutenberg collaborated on earthquake measurement at the California Institute of Technology.
Richter magnitude scale: A logarithmic measure of earthquake size based on the amplitude of recorded seismic waves. Gutenberg co-developed this scale with Richter for comparing local earthquakes.
Earth's internal structure: The arrangement of Earth’s crust, mantle, and core, inferred from geology, gravity, and seismic waves. His boundary measurement helped define the planet’s layered interior.
P wave: A compressional seismic body wave that travels through solids and fluids. P-wave paths and travel times change sharply when they enter the outer core.
Emil Wiechert: A German geophysicist who developed influential models of Earth’s interior and seismic instruments. Wiechert’s work formed part of the German geophysical tradition in which Gutenberg trained.
Moment magnitude scale: A logarithmic measure of earthquake size based on seismic moment, suitable for very large earthquakes. It later addressed limitations of the magnitude scales Gutenberg and Richter helped develop.
Gutenberg discontinuity: The sharp seismic transition at the base of Earth’s mantle, marking the top of the liquid outer core. This named boundary commemorates the seismic interpretation Gutenberg established.
S wave: A shear seismic body wave that travels through solids but not through fluids. The disappearance of direct S waves beyond certain distances supports a liquid outer core.