Geology: Geomagnetic data captured in crystals

Researchers have used silicate crystals to determine the strength of the Earth’s geomagnetic field around 3.2 billion years ago. Their findings should help to shed light on the evolution of the Earth’s deep interior, surface environment and atmosphere.
John A. Tarduno and colleagues studied silicate crystals from well preserved igneous rocks found in South Africa’s Archaean Kaapvaal craton. The crystals contain minute magnetic inclusions, and the team calculate that 3.2 billion years ago, the Earth’s geomagnetic field strength was within fifty per cent of the present-day value. This means that there was probably a viable magnetosphere to shelter the planet from solar wind erosion at that time.
Little is known about the strength of the Earth’s geomagnetic field before 2.8 billion years ago, so the new data offer a welcome insight into the Earth’s geomagnetic history.
CONTACT
John A. Tarduno (University of Rochester, NY, USA)
Tel: +1 585 275 5713; E-mail: john@earth.rochester.edu
David J. Dunlop (University of Toronto, Canada) N&V author
Tel: +1 905 828 3968; E-mail: dunlop@physics.utoronto.ca