Earth's Original Crust Found in Canadian Shield

Nick Mcbride
March 21, 2017

Geologists have found remnants of Earth's 4.2 billion years old crust in rock samples from Canada.

Throughout its 4.5 billion-year history, the Earth's crust - the thin outer layer of the planet - has been recycled several times, and most of the original crust has always been forced deep below the surface.

The discovery, on the Eastern shores of the Hudson Bay in northern Quebec, gives scientists an unprecedented insight into how the Earth was formed. In the successive eras, the planet's outermost layer has recycled itself several times while the older crusts have been forced below the surface.

Close-up of 2.7 billion-year-old continental crust from Nunavik, northern Quebec showing a complex history of re-melting of oceanic-type rocks that were older than 4.2 billion years.

There is much about Earth's ancient crust that scientists don't understand because most of the planet's original crust simply isn't around any longer to be examined.

Recreating the nature of Earth's first crust is hard because a geologic activity has created the turnover that drove most of it back into Earth's interior. "We're missing basically all the crust that was present about 4.4 billion years ago".

Jonathan O'Neil, of McGill University in Montreal and Dr. Richard Carlson, from the Carnegie Institution for Science in Washington DC, led the study. Nevertheless, he also pointed out that the old crust looks very similar to what scientists assume that the crust uses to be. The oldest portions of Earth's modern crust are about 2.7 billion years old, leaving a 1.9 billion year blank spot in our knowledge of early Earth. However, some pieces of earlier crust remained evasive.

The geologists discovered the chunk of rock enveloped by granite in an area known as "The Canadian Shield" which forms the ancient geological core of the North American continent.

This makes the volcanic rock that emerged in Hudson Bay the oldest geological treasure ever uncovered. O'Neil stated that he believes that this was once part of the bottom of Earth's first oceans.

However, it "only" lasts for about 70 million years before decaying into another isotope, neodymium-142.

Earth's composition is unlike any other known planet or a moon, with rocky crusts forming and moving over the surface.

The team is optimistic that their new method will expand human understanding of early Earth. This isotope, which existed only for about 500 million years after the Earth formed, decayed into neodymium-142.

Though the findings don't answer every question about Earth's early history, they do shed some light on its development.

The discovery could even be useful in helping us to better understand other planets in our solar system, Mr. O'Neil said.

Other reports by VgToday

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