Andrija Mohorovičić and the Mohorovičić Discontinuity


Andrija Mohorovicic
(1857 – 1936)

On January 23, 1857, Croatian meteorologist and seismologist Andrija Mohorovičić was born. He is best known for the eponymous Mohorovičić discontinuity, i.e. he boundary between the Earth’s crust and mantle discovered by him – and is considered a founder of modern seismology.

Andrija Mohorovičić Background

Andrija Mohorovičić proved to be a talented student from early age. By the age of 15, he spoke English, French and Italian and learned German, CzechLatin and Ancient Greek as well. He enrolled at the Faculty of Philosophy of the University of Prague and studies with prominent professors, such as Ernst Mach.  Afterwards, he was occupied as a teacher at the grammar school in Zagreb and in Osijek. He made systematic studies and both invented and constructed instruments to observe precipitation in Croatia and Slavonia. At a nautical school in Bakar near Rijeka, he was able to teach mathematics, physics and meteorologyMohorovičić established a meteorological station and he maintained continuous meteorological observations. In his observations, he also included the movement of air and the cloud using the nephoscope, which he constructed.

Mohorovičić defended his dissertation “On the Observation of Clouds, and the Daily and Annual Cloud Period in Bakar” in 1893 and taught courses in geophysics and astronomy at the Faculty of Philosophy in Zagreb. The scientist and teacher also became a member of the Yugoslav Academy of Sciences and Arts in Zagreb. [1] On 13 March 1892, he observed the tornado in Novska, which picked up a 13-ton railway carriage with fifty passengers and threw it 30 m. He observed also the “vihor” (whirlwind) near Čazma in 1898 and studied the climate in Zagreb. Mohorovičić was the first person to describe atmospheric rotors with a horizontal axis, which he observed during bora-wind episodes in the northern Adriatic.

Mohorovičić Discontinuity

To one of Mohorovičić’s biggest contributions to science belogs the famous Mohorovičić Discontinuity, which was discovered around 1910 and it can be described as the boundary between the Earth’s crust and the mantleMohorovičić realized that the velocity of a seismic wave is related to the density of the material that it is moving through and interpreted the acceleration of seismic waves within Earth’s outer shell as a compositional change within the Earth. Therefore, he concluded, must the acceleration be caused by a higher density material being present at depth. Mohorovičić determined that the basaltic oceanic crust and the granitic continental crust are underlain by a material which has a density similar to an olivine-rich rock such as peridotite. [2]

At yovisto, you may more about the Science of Natural Disasters in a video lecture by Dr. David Percovici at Yale University.

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