The earth's magnetic field is on average dipolar (similar to that generated by a bar magnet at the center of the earth) and is sustained by fluid motions in the outer core. Since the 1950's, it has been known that the polarity of the magnetic field changes episodically (with polarity intervals ranging from 10,000 years to 30 million years). The intensity of the geomagnetic field also changes greatly over periods as short as a few hundred years, though the record of past intensity fluctuations is poorly known. In contrast, directional changes over the past ~180 million years are well known from studies of lineated marine magnetic anomalies. Paleomagnetic and geomagnetic research in GRD is primarily aimed at understanding these past changes in the direction and intensity of the field. In addition, magnetic data (both anomalies and the magnetization of samples) can be used to study a variety of geologic problems ranging from plate tectonic reconstructions to the pattern of crustal accretion at mid-ocean ridges or the details of magma chamber processes.

People: Lisa Tauxe, Steve Cande, Jeff Gee, Yongjae Yu

Recent and ongoing research projects include:

1. A paleointensity record from the ocean crust
2. Mapping sea surface magnetic anomalies
3. Characterizing the time-averaged magnetic field
4. Long term variations in geomagnetic intensity
5. Magnetization of meteorites and lunar samples
6. Applications of magnetic data to fabric development in cumulates