A chunk of Earth’s crust, about 3.8 billion year-old, has been found in Greenland. It is the oldest known such chunk ever found in the earth’s crust. The substantial rock is a type known as ophiolite. This signature of tectonic plate movement is an important find as it provides the best evidence of the continental drift.
Until now, the oldest example of ophiolite was that in China, which dates back to 2.5 billion years ago. To add to, its identification had been in question as well.
The find reveals that the continental drift has been going on for at least a billion years longer than what was previously thought.
According to researchers, plate tectonics probably began soon after the first solid crust grew heavy enough capable of sinking into the then-molten mantle lying below it.
The fragment of ophiolite embedded in the Isua supracrustal belt in south-west Greenland has been analyzed to be a part of a distinctive layered deposit — called “sheeted dikes.”
Image Credit: Science