The following essay is reprinted with permission from The Conversation, an online publication covering the latest research.
We have discovered the oldest meteorite impact crater on Earth, in the very heart of the Pilbara region of Western Australia. The crater formed more than 3.5 billion years ago, making it the oldest known by more than a billion years. Our discovery is published today in Nature Communications.
Curiously enough, the crater was exactly where we had hoped it would be, and its discovery supports a theory about the birth of Earth’s first continents.
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The very first rocks
The oldest rocks on Earth formed more than 3 billion years ago, and are found in the cores of most modern continents. However, geologists still cannot agree how or why they formed.
Nonetheless, there is agreement that these early continents were critical for many chemical and biological processes on Earth.
Many geologists think these ancient rocks formed above hot plumes that rose from above Earth’s molten metallic core, rather like wax in a lava lamp. Others maintain they formed by plate tectonic processes similar to modern Earth, where rocks collide and push each other over and under.
Although these two scenarios are very different, both are driven by the loss of heat from within the interior of our planet.
We think rather differently.
A few years ago, we published a paper suggesting that the energy required to make continents in the Pilbara came from outside Earth, in the form of one or more collisions with meteorites many kilometres in diameter.
As the impacts blasted up enormous volumes of material and melted the rocks around them, the mantle below produced thick “blobs” of volcanic material that evolved into…
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