Research Supports 'Snowball Earth' Theory

EARLY EARTH

The many season of Snowball earth.

by Staff Writers
UPI Correspondent
New Haven (UPI) Nov 02, 2006
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.

Source: United Press International

EARLY EARTH

Jumping The Oxygen Gap

Seattle WA (SPX) Nov 03, 2006
Vertebrate creatures first began moving from the world's oceans to land about 415 million years ago, then all but disappeared by 360 million years ago. The fossil record contains few examples of animals with backbones for the next 15 million years, and then suddenly vertebrates show up again, this time for good.

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