NIU geologist helping to shed light
on inner workings of our planet

by Tom Parisi

NIU geologist Mark Frank is a member of an international team of scientists who recently published findings in the Proceedings of the National Academy of Sciences that will assist researchers for years to come in their study of our planet’s internal structure and composition.

“Researchers don’t really know that much about the interior of Earth, or any planetary body for that matter,” Frank said.

“One way scientists learn about Earth’s inner composition is by studying large earthquakes, which release significant quantities of energy that are transmitted away from the quake’s focus by seismic waves,” he added. “As they pass through the interior, the waves experience changes in velocity, which indicate changes in density of material or composition.”

Scientists use observations of seismic waves to create laboratory models of the planet’s interior. “A complete understanding of the layering within the deep Earth requires a correlation of the observed seismic data with experimentally derived values,” Frank said.

The correlation is critically dependent on the accuracy of pressure measurements up to 364 gigapascals, a pressure at the center of the Earth at high temperature. Large uncertainties in the currently used pressure scales hamper scientific inquiry, however.

The PNAS study provided new compression data for gold, platinum, solid neon and sodium chloride that will help researchers address the ambiguities. The researchers also devised “thermal equations of state” for those materials. The equations compute how the materials will shrink under increasing pressure.

“We’re helping to create a set of standards for scientists who work in this field,” Frank said. “Ultimately this will advance our understanding of fundamental high-pressure phenomena and the chemistry and physics of the Earth’s interior.”

Other members of the research team included scientists from the Geophysical Laboratory at the Carnegie Institution of Washington, the University of Tokyo and the University of Chicago.

The experimental work was performed at Argonne National Laboratory’s Advanced Photon Source and is supported by the National Science Foundation, the U.S. Department of Energy, the State of Illinois and the Carnegie Institution of Washington.

6-4-07