Matsuyama, Motonori (1884–1958)

Japanese geophysicist who determined that the earth's magnetic field reverses its polarity periodically throughout its geological history. He also pioneered the use of gravimetry in finding geological structures below the earth's surface.

In 1930, Matsuyama began studying magnetism preserved in rocks. It was known as early as 1906 that some rocks were magnetized such that they pointed toward magnetic north, while the magnetism of other rocks pointed in the opposite direction. Matsuyama studied these magnetic anomalies and suggested they were due to a reversal in the polarity of the earth's magnetic field. The Matsuyama Epoch, a major polar reversal occuring approximately 0.5–2.5 million years ago, is named after him.

Matsuyama was born in Usa, Japan, and studied mathematics and physics at Hiroshima Normal College and Imperial University, Kyoto. He became a professor at Imperial University in 1913 where he studied gravity determination using pendulum techniques. He carried out extensive gravity surveys in Manchuria, Korea, and in the Japan Trench.