The following essay has been reproduced with permission conversationan online publication that covers the latest research.
We discovered the oldest met stone impact crater on Earth in the heart of the Pilbara region of Western Australia. The crater formed over 3.5 billion years ago and became the oldest Over 1 billion years. Our findings are published today Natural Communication.
Strangely enough, the crater is exactly where we wanted it, and its discovery supports the theory of the birth of the first continent of Earth.
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The first rock
The oldest rock on Earth formed over 3 billion years ago and is located in the core of most modern continents. However, geologists still cannot agree how or why they were formed.
Nevertheless, these have these agreements The early continents It was important for many chemical and biological processes on Earth.
Many geologists believe that these ancient rocks were formed On the hot plume It rose from above the Earth’s molten metal core, like the wax of a lava lamp. Others maintain what is formed by Plate Structure Process It resembles a modern Earth where rocks collide and push each other.
These two scenarios are very different, but both are driven by the loss of heat from within our planet.
We think about it quite differently.
A few years ago we published it paper It suggests that the energy required to create the Pilbara continent comes from outside the Earth in the form of one or more collisions with metstones several kilometers in diameter.
When the impact exploded a huge amount of material and melted the surrounding rocks, the mantle below produced a thick “blob” of volcanic material. Evolved into a continental crust.
Our evidence then lies in the chemical composition of small crystals of mineral zircon for the size of the grains of sand. But to persuade other geologists, they needed more persuasive evidence, preferably something that people could see without the need for a microscope.
So, in May 2021 we started a long drive north from Perth for a two-week fieldwork in Pilbara.GSWA) Look for a crater. But where should I start?
A reliable GSWA vehicle looking for crushed cones in a typical Pilbara landscape.
Chris Kirkland from Curtin University
The beginning of a coincidence
Our first target was a rare layer of rock known as members of Antarctic Creek, harvested on the side of a dome about 20km in diameter. The Antarctic Creek members are only about 20 meters thick and consist primarily of sedimentary rocks sandwiched between several kilometres of dark basaltic lava.
However, it is included sphere– Droplets formed from molten rocks thrown during impact. But these drops may have traveled all over the globe, perhaps from the currently destroyed crater.
After consulting with GSWA maps and aerial photographs, we found an area to begin our search along the dusty track in the center of the Pilbara. We parked off-road vehicles, followed separate paths across the outcrop, and agreed to meet in an hour later, discussing what we found and taking a bite, if we wanted more than expected.
A large shed-like crushed cone on the rocks of members of Antarctic Creek on the Discovery Site. The rock on the left, on the hill, is basalt that lies directly on the grinding cone.
Tim Johnson of Curtin University
Surprisingly, when we got back in the car, we all thought we had found the same thing: crushed cones.
The crushed cone is a beautiful, delicate branched structure that is different from badminton shuttlecocks. They are the only characteristic of impact visible to the naked eye, and can only be formed in nature following the impact of metstones.
Within an hour of search, we found exactly what we were looking for. We literally opened the 4WD door and stepped into the floor of a huge, ancient impact crater.
Annoyed, I had to take some photos and grab some samples and then move to another site, but decided to go back as soon as possible. Most importantly, you need to know how old the crushed cone is. Have you discovered the oldest known crater on the planet?
It turns out we had.
It is a 1 meter high grinding cone “hut”, with a gentle hill of pilbara in the background.
Chris Kirkland from Curtin University
Go back there
With several laboratory studies under our belt, we returned to the site in May 2024 to examine the 10-day evidence in more detail.
Grinding cones are everywhere, developed in most of Antarctica Creek’s members, and tracked them for hundreds of meters on the gentle hills of Pilbara.
Our observations showed that there was no evidence of impact shock over the layer of ground cone, and a thick layer of basalt. This meant that this influence had to be the same age as Antarctica member rock. I know this was 3.5 billion years ago.
Delicate grinding cones in rocks typical of members of Antarctic Creek.
Tim Johnson of Curtin University
We were old and had the oldest impact crater record on the planet. Perhaps our idea of the ultimate origin of the continent was not so upset.
Serendipity is amazing. As far as we know, except for the traditional owners of Nyamal, no geologist has looked at these wonderful features since they were formed.
Like some Others in front of uswe argued that the impact of metstones played a fundamental role in the geological history of our planet, as they clearly had on the moon and on our crater. Other planets, moons, asteroids. Now we and others have the opportunity to test these ideas based on difficult evidence.
Who knows the number of ancient craters undiscovered in the ancient cores of other continents? Finding and studying them not only creates the land where we all live; The origin of life itself.
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