Earth's plate tectonics may have started more than 4 billion years ago

Washington, Nov 27 : A new research by geochemists at the University of California, Los Angeles (UCLA), has suggested that plate tectonics may have started more than 4 billion years ago, which is much earlier than scientists had believed.

The Earth is 4.5 billion years old. While some scientists think plate tectonics started 3.5 billion years ago, others say that it began even more recently than that.

The research is based on their analysis of ancient mineral grains known as zircons found inside molten rocks, or magmas, from Western Australia that are about 3 billion years old.

Zircons are heavy, durable minerals related to the synthetic cubic zirconium used for imitation diamonds and costume jewelry. The zircons studied in the Australian rocks are about twice the thickness of a human hair.

Michelle Hopkins, a UCLA graduate student in Earth and space sciences, analyzed the zircons with UCLA's high-resolution ion microprobe, an instrument that enables scientists to date and learn the exact composition of samples with enormous precision.

The microprobe shoots a beam of ions, or charged atoms, at a sample, releasing from the sample its own ions, which are then analyzed in a mass spectrometer.

Scientists can aim the beam of ions at specific microscopic areas of a sample and conduct a high-resolution isotope analysis of them without destroying the object.

"The microprobe is the perfect tool for determining the age of the zircons," said geochemistry professor Mark Harrison, director of UCLA's Institute of Geophysics and Planetary Physics.

The analysis determined that some of the zircons found in the magmas were more than 4 billion years old.

They were also found to have been formed in a region with heat flow far lower than the global average at that time.

"We are proposing that there was plate-tectonic activity in the first 500 million years of Earth's history," said Harrison. "We are reporting the first evidence of this phenomenon," he added.

According to Harrison, "Unlike the longstanding myth of a hellish, dry, desolate early Earth with no continents, it looks like as soon as the Earth formed, it fell into the same dynamic regime that continues today."

"Plate tectonics was inevitable, life was inevitable. In the early Earth, there appear to have been oceans; there could have been life - completely contradictory to the cartoonish story we had been telling ourselves," he added.

"We're revealing a new picture of what the early Earth might have looked like," said lead author Michelle Hopkins, a UCLA graduate student in Earth and space sciences.

ANI