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First continent on earth formed like Iceland

Source : IANS
Last Updated: Fri, May 30, 2014 09:26 hrs

Toronto: The timing and mode of continental crust formation is a controversial topic but geochemical analysis of a newly discovered rock unit from Canada has shown that the first continent on earth may have formed in a way modern-day Iceland came into existence.

The rocks about four-billion-year-old showed crust-forming processes that are very similar to those occurring in present-day Iceland.

"This provides the first physical evidence that a setting similar to modern Iceland was present on the early earth," said Jesse Reimink from University of Alberta in Canada, who collected and studied rock samples from the Acasta Gneiss Complex in Canada.

These ancient rocks are among the oldest samples of protocontinental crust that we have, and may have helped jump-start the formation of the rest of the continental crust, he added.

Continents today form when one tectonic plate shifts beneath another into the Earth's mantle and cause magma to rise to the surface, a process called subduction.

It is unclear whether plate tectonics existed 2.5 billion to four billion years ago or if another process was at play, Reimink said.

One theory is the first continents formed in the ocean as liquid magma rose from the Earth's mantle before cooling and solidifying into a crust.

Iceland's crust formed when magma from the mantle rises to shallow levels, incorporating previously formed volcanic rocks.

For this reason, Reimink added Iceland is considered a theoretical analogue on early earth continental crust formation.

The study appeared in the journal Nature Geoscience.




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