The Rock Dispute
In the late 1700's and early 1800's, a dispute developed among geologists about how rocks are formed. Abraham Gottlob Werner, a German mineralogist, believed that an ocean once covered the entire earth. Werner and his followers declared that chemicals in the water slowly settled to the bottom, where they formed layers. The oldest, bottom layer was supposedly composed of granite. These theorists thought the earth had been formed completely by the settling of chemical materials as ocean waters gradually filled in and evaporated. They also thought that no further changes in the earth would ever occur.
A widely different idea was held by James Hutton, a Scottish philosopher and farmer. Hutton and his supporters believed that some rocks were formed by the cooling of hot lava from volcanoes. In 1795, in a work called Theory of the Earth, Hutton presented what would later be called the principle of uniformitarianism. He claimed that the earth was gradually changing and would continue to change in the same ways. He said these changes could be used to explain the past. He died in 1797 before other scientists accepted his ideas. In 1802, John Playfair, a Scottish mathematician, published Illustrations of the Huttonian Theory. This work presented Hutton's ideas clearly and with illustrations. It became a leading guide to geological thinking. The argument over the origin of rocks was settled in the early 1800's after two of Werner's most famous students, Leopold von Buch and Alexander von Humboldt, accepted uniformitarianism.
Excerpt adapted from the
"Geology" article, The World Book Encyclopedia © 1999