Lamont 26th W.S. Jardetzky Lecture
The History of the Earth's Magnetic Field Strength Over the Last Four Million Years: An Updated Global View
with Dr. Lisa Tauxe, Distinguished Professor Emerita, Scripps Institution of Oceanography, University of California, San Diego.
In 1600, William Gilbert published the first book examining the Earth’s magnetic field from a global perspective. He famously said, “The Earth itself is a great magnet”. While this is mostly true, there are significant departures from this simple bar magnet assumption. For example, the Earth’s magnetic field “flips” occasionally, and other effects complicate our ability to track the motions of continents accurately. If the magnetic field were like that of a simple bar magnet centered in the Earth and aligned with the spin axis (a geocentric axial dipole), the field strength would be twice as strong at the poles than at the equator. The present magnetic field has a North-South hemispheric asymmetry in field strength that appears to persist over at least 100,000 years. Some modeling suggests that this asymmetry is only expected when the magnet bar magnet is strong (like today’s) and should disappear when the field is weaker (like it was, say, five million years ago). To test this hypothesis, we require estimates of the ancient field strength from around the world from geologic records. In this talk, I will talk about how lava flows retain a record of the Earth’s magnetic field and what the results are from a global campaign to obtain data to address this problem.
Host: Dr. Steven Goldstein, Interim Director, Lamont-Doherty Earth Observatory.
The Earth Science Colloquium Series, sponsored by Lamont-Doherty Earth Observatory and Columbia University Department of Earth and Environmental Sciences (DEES), provides a lively forum for discussing a wide variety of topics within the Earth sciences and related fields. Colloquia are attended by the full range of scientific and technical staff at LDEO. Colloquium attendance is required of all pre-orals DEES graduate students.
