• Grand Canyon Expedition (Caltech and Carnegie Institution), 1939
    Credit: Courtesy of the Archives, California Institute of Technology



The Division of Geological and Planetary Sciences began as the department of geology at Caltech in 1926.

The Seismological Laboratory existed before the formation of Caltech's geology department, having been founded by the Carnegie Institution of Washington in 1921. After 1926, the lab was managed jointly by the Carnegie Institution of Washington and the California Institute of Technology, until administration of the Seismo Lab was transferred to Caltech in 1937. In the 1920s Charles Richter, a Caltech physics graduate working at the Seismo Lab, developed a formula for comparing the magnitudes of Southern California earthquakes. In the 1930s Beno Gutenberg joined both the division and the Seismo Lab, and he and Richter together developed the Richter Scale we use today. Hugo Benioff, also a division professor and member of the Seismo Lab, studied seismically active subduction zones, or "Benioff-Wadati" zones.

Geology Field Trip, 1939
Credit: Courtesy of the Archives, California Institute of Technology

Paleontologist Chester Stock helped to establish the principles of mammalian evolution. In addition to chairing the division for a period, he also served as chief science curator at the Los Angeles County Museum.  Many of the fossils he collected are now at the Natural History Museum of Los Angeles County.

Dr. Stock was the chief science curator at the Los Angeles County Museum of History, Science and Art from 1948–50. This only became the Natural History Museum after the Art Department relocated to Hancock Park in 1964.

Dr Stock and his colleagues and students are renowned for collecting vertebrate fossils ranging from dinosaurs to mammals from sites throughout the American West and northern Mexico. Most of those fossils were transferred to the LA County Museum after Dr. Stock's death. The Page Museum has a site-specific collection that is restricted to fossils from the La Brea Tar Pits. Dr. Stock published some classic monographs on fossil mammals from the tar pits but most of the La Brea fossils that he studied were either collected by UC Berkeley or were collected by LA County Museum staff before Dr Stock arrived in Pasadena to co-found Caltech's Department of Geology.

The Charles Dayton Arms and Seeley W. Mudd Laboratories of Geological Sciences (Arms and North Mudd) were built in 1938.


During this time, the division grew to include programs of study and research in geochemistry and planetary science.

The entry into geochemistry around 1950 was largely at the expense of paleontology and marked a remarkable transition to a more quantitative approach to earth science. The entry into planetary science in the 1960s took advantage of the new U.S. space program of unmanned exploration and the proximity of the Jet Propulsion Laboratory. At that time, the division adopted its current name.

Gerald Wasserburg with vacuum line, ca 1953–54
Credit: Courtesy of the Archives, California Institute of Technology

Geochemist Clair Patterson determined the age of the earth as 4.55 billion years, building on work begun at University of Chicago. He also studied the buildup of lead in the environment and in the human body, and his work in this area, which continued into the 1980s, contributed to the removal of lead from gasoline, food containers, and paint.

Paleoecologist Heinz Lowenstam discovered that some animals manufacture magnetic minerals in their bodies. Recently, researchers building on this work found that homing pigeons use magnetite in their beaks to help them navigate.

Robert Sharp and other geologists took long-range looks at the flow processes in the ice of glaciers, and people like Leon Silver concentrated on the origins of Earth's very old rocks, particularly in western North America. Silver's work later made him a natural for training Apollo astronauts on what to look for on the moon.


Scientists in the division did intensive work on the isotopes in various elements, developing and refining isotopic age-dating techniques that are applicable to many meteoric, terrestrial, and lunar materials. They were responsible for key contributions to the analysis of lunar material and the interpretation of images and other data from many spacecraft missions. They performed studies of the earth's climate using isotopic means and made possible a new understanding of both ancient climates and climatic changes over the last thousand years.

In addition to analyzing data returned to earth from increasingly sophisticated space exploration missions, planetary scientists contributed to the design of instrumentation to increase the power of existing telescopes. One—James Westphal—designed the Space Telescope's Wide-Field/Planetary Camera. A combination of high-pressure experimentation and solid-state theoretical work improved understanding of the structure of the earth's interior.

The Seeley G. Mudd Building of Geophysics and Planetary Sciences (South Mudd) was built in 1974, and this marked the move of the Seismological Laboratory onto campus from its previous location at the Kresge laboratory.


During this period, the division has expanded in new directions, building strong programs in geobiology and in environmental science, including atmospheric science and oceanographic activities that were previously not present at Caltech or were only to be found in the engineering and applied science division. This growth in strength has taken advantage of collaborative efforts, including joint appointments, with other divisions. It has also benefited from existing and sustained strength in geology and geochemistry.

Ronald and Maxine Linde Center for Global Environmental Science
Although geobiology has had a long association with Caltech, through the pioneering efforts of Lowenstam and the subsequent research of Joe Kirschvink (particularly on the role of magnetism), the division recognized the importance of biology in earth evolution and successfully sought to build this area. The division has also established a Tectonics Observatory, shown leadership in computational geophysics, and played a leading role in the discovery of dwarf planets, including a body larger than Pluto.

A remarkable feature of the division in the past decade or so has been the hiring of more than half the current faculty as older faculty have graduated to emeritus status. Our young group of highly active, influential, and successful young scientists attest to the continuing vitality and world leadership of the division.