Geologists have long suspected that one of the oldest regions of the Australian continent, the Pilbara craton, contains traces of one of the oldest collisions between our planet and another celestial body. Recently, they managed to confirm this by discovering debris and other rocks on its surface that only form in the case of really powerful meteor strikes.
Earth’s oldest continents
A team of Australian scientists say they have found the oldest impact crater on Earth. It’s about the evidence of a collision with a large celestial body they found while exploring the Pilbara craton in Western Australia.
As we know, continents on Earth are formed as a result of the movement and collision of lithospheric plates. When the crust is washed away, new mountains are formed, which are erased by erosion over time. This means that continental crust is being renewed all the time, and the further we delve into the past, the harder it is for us to find areas that formed then.
Even the Precambrian plates were mostly formed between 1 and 2 billion years ago. The oldest parts of the landmass are called cratons. They are at the base of all continents, but are so rare that scientists cannot even be sure that there were large continents of which they were a remnant.
The most ancient craters
All of this directly relates to the question of the oldest craters on Earth. After all, scientists have this crazy idea that it was meteorite impacts that once caused the first cratons to form. Allegedly, they could compact the igneous rocks and make them more stable. There is no confirmation of this, but there are craters on the oldest parts of the land.
The fact that some large impact trace must be somewhere in the Pilbara has long been suspected. This was evidenced by tiny zircon crystals in samples from local rocks. They are formed specifically by meteor strikes, but the scientists wanted some evidence that would be visible under more than just a microscope.
Therefore, they traveled to the Pilbara and subsequently found near the North Cone geologic structure characteristic reticulated formations that looked like the feathers of a tennis shuttlecock. These are what are called sedimentary cones. And they are definitely formed by meteorite impacts.
In addition, scientists have found so-called spherules. These are small spheres that form when the rock melted as a result of the impact cools down. All of this indicates that there was indeed a cosmic collision at some point in time. When? This has been answered by subsequent studies that show the impact occurred about 3.5 billion years ago.
That pretty much exceeds the previous record for the age of the crater, which is about 2.2 billion years ago. As for the shock structure itself, it is now almost completely destroyed, but its diameter should have reached 100 km.
According to phys.org
