James' World 2

Click the link below the picture

.

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.

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 continental crust.

Our evidence then lay in the chemical composition of tiny crystals of the mineral zircon, about the size of sand grains. But to persuade other geologists, we needed more convincing evidence, preferably something people could see without needing a microscope.

So, in May 2021, we began the long drive north from Perth for two weeks of fieldwork in the Pilbara, where we would meet up with our partners from the Geological Survey of Western Australia (GSWA) to hunt for the crater. But where to start?

.

.

.

Click the link below for the complete article:

.

__________________________________________