Physicists of College Seek Subterranean Radioactive Source

Interior radioactivity as a cause for earthquakes and volcanic eruptions is a possibility being explored by the research program of Harvard's Geophysical Laboratory, whose field experiments involve timed explosions over large bedrock areas.

Combining such field work with the high-pressure laboratory research of Nobel Prize winner Percy W. Bridgman, Hollis Professor of Mathematics and Natural Philosophy, the new project is designed to give scientists a better picture of the nature of the earth's insides, in addition to determining location of the main mass of the planet's radioactive material.

Behind reinforced concrete walls in the Dunbar Geophysical Laboratory. Professor Bridgman has duplicated pressures existing 200 miles below the earth's surface, forces, however, that are minute in comparison with those existing at the center of the earth. Under such conditions, solid rock becomes highly plastic and considerably more dense.

Though most geologists believe that radioactive material occurs only in the earth's outer crust, geophysical research may reverse this theory.

Combine Lab, Field Work

Correlation of field observations with experimental laboratory reactions is the crux of the research problem according to Francis Birch, professor of Geology and director of the Geophysical Laboratory. He hopes that large scale field work will show whether laboratory determined pressure gradients continue evenly down to greater depths.

Exact purpose of the field explosions is to produce seismic reactions that can be calculated in order to provide a more accurate conception of the makeup of concentric shells that comprise the structure of the earth. It is hoped that further experiments will offer clues to the chemical changes produced by high pressures.