Research supports 'Snowball Earth' theory

NEW HAVEN, Conn., Nov. 2 (UPI) -- A U.S. study finds Earth's magnetic field has changed little during 2 billion years, lending support to the "Snowball Earth" hypothesis.

The finding by David Evans of Yale University and colleagues was previously assumed, rather than tested.

The Earth's magnetic field leaves a tell-tale signature in certain rocks, which can be used to infer information about the latitude at which they formed, Evans said. But if the early Earth's magnetic field was markedly different to today's axial dipolar field, some of those interpretations could be off the mark.

Evans compiled a global database of evaporite rocks dating to 2 billion years. He found the rocks' magnetic properties suggest that, as now, the Earth's magnetic field was predominantly an axial dipole on average, suggesting the Neoproterozoic "Snowball Earth" was probably shrouded in ice.

The research is detailed in the current issue of the journal Nature.