Earth’s Inner Core Age and Paleomagnetic Expression
Keynote Lecture Series
Lecture Date and Time (US Mountain Time):
Thursday, August 27, 2020 - 12:00
The age of Earth’s enigmatic inner core (IC) is unknown with estimates ranging from 500 Myr to the age of the Earth itself. In this talk we review how the IC is thought to have formed and why such a range of age estimates persists. Given its inaccessibility, we discuss how the nucleation and continual growth of the IC may have influenced convection in the outer core and its observable paleomagnetic expression at Earth’s surface. We highlight numerical dynamo models driven by a whole-planet thermal evolution model that show the geodynamo could have transitioned from a multipolar to dipolar regime around 1.7 Ga, then to a weak-field dynamo around 1.0 Ga, and finally to a strong-field dipole following IC nucleation around 650 Ma that is maintained to the present day. Recent paleomagnetic observations from the Neoproterozoic are consistent with a weak non-dipolar dynamo, supporting the possibility of a young IC. Finally, we discuss several core material properties that are likely to have a first-order effect on the magnetic evolution of the Earth, including the magnitude and depth-dependence of the thermal conductivity.
Peter Driscoll received his Ph.D. degree in Earth and planetary science from Johns Hopkins University in 2010. He was a Bateman postdoctoral fellow in the geology and geophysics department at Yale University from 2010 to 2013, and has since been the planetary interiors and evolution postdoctoral fellow in the NASA Virtual Planetary Laboratory at the University of Washington in Seattle. He is now a Staff Scientist in the Geophysics Group at the Carnegie Institution for Science, Department of Terrestrial Magnetism.