Australia has found the oldest crater on Earth

A team of researchers from Curtin University and a number of partners have made a landmark discovery in the heart of the Pilbara region of Western Australia. The work is published in the journal Nature Communications.

Scientists have long been trying to understand how the oldest parts of the Earth's crust were formed. There have been several hypotheses, from "hot mantle plumes" like wax in a "lava lamp" to classic plate collisions. But this discovery supports a different idea: the formation of continents may be due to a series of powerful impacts of large meteorites, which "plumped up" the mantle and formed the continental crust.

Why scientists were looking for a crater in the Pilbara

• Age of rocks: The Pilbara rocks are among the oldest on Earth, more than 3 billion years old.
• Hypothesis: A few years ago, researchers suggested that the Pilbara should preserve signs of impact events that laid the energy to "build" the first continents.

Operation Crater Finder

In May 2021, geologists embarked on an expedition focusing on the so-called Antarctic Creek Member, a thin layer of sedimentary rock between thick layers of basaltic lava. Previously, spherules - tiny droplets of rock ejected during a meteorite impact - have been found in this sedimentary rock.

Just an hour into the search, the team came across shock structures called "shatter cones" (shatter cones). These unusual, fan-shaped patterns appear only in a meteorite impact - and nowhere else in the natural environment. In the researchers' words, they literally "came off the car and immediately ended up at the bottom of a huge fossil crater."

Why is this crater important?

1. Confirmation of theories. The discovery strengthens the hypothesis that meteorite impacts played an important role in the formation of early continents.
2. New perspectives. Ancient impact structures may also be present in other continental cores, but have remained unrecognised until now. Such findings will help to better understand Earth's early evolution and possibly the conditions for the origin of life.

The fracture cones turned out to be in rocks of the same age as the "Antarctic-Creek Horizon" - about 3.5 billion years old. This makes the new crater the oldest known (a billion years older than the previous record holder). Scientists will return to the site in 2024 for more research. The cone-shaped structures can be traced for hundreds of metres.

According to scientists, a series of such impacts could have released enough heat and energy to form "strata" of magma that later became continental crust. More locations and rocks will now have to be analysed to establish how global this process was.