☄️ Date change for Earth's oldest impact crater

Earth's oldest impact crater just got a serious makeover: 470 million years younger than previously thought! Located in Western Australia, the North Pole Dome was previously dated at 3.47 billion years. A new study, published in Geology, brings it back to about 3 billion years.

To reach this new estimate, scientists from Curtin University used advanced dating techniques on minerals found in the crater's rocks. Zircon, a particularly resistant mineral, played a central role. By analyzing its unusual crystal shapes, the researchers were able to identify the traces left by the meteorite impact. These results are consistent with those obtained from other minerals such as apatite, reinforcing the reliability of the proposed age.


This new dating still makes the North Pole Dome the oldest known impact crater on Earth, exceeding the next one, Yarrabubba, also in Australia, by nearly 800 million years. It is also the only recognized example from the Archean eon, a period between 4 and 2.5 billion years ago when the first continents were forming.

Researchers emphasize the difficulty of dating such ancient craters. Rocks subjected to heat, fluids, and pressures over billions of years often lose the original traces of the impact. Zircon, a true "mineral clock," helps bypass this problem by retaining a memory of intense thermal events.

This discovery sheds new light on Earth's early history. Knowing that such a powerful impact occurred 3 billion years ago helps us understand how meteorites shaped our planet. The North Pole Dome crater is not just the oldest: it is a key to deciphering Earth's geological infancy.

Shatter cones: unique impact signatures

When a meteorite strikes Earth at high speed, the shock wave propagates through the ground and deforms rocks in a very specific way. One of the most characteristic traces is the formation of shatter cones, also known as percussion cones. These are cone-shaped or fan-shaped fractures visible to the naked eye on rock blocks. Their presence is considered almost certain evidence of an impact, as no natural geological process reproduces them.

These structures form in seconds under colossal pressures, on the order of 2 to 30 gigapascals. Their size ranges from a few centimeters to several meters. In the case of the North Pole Dome, the initial study relied on their presence to date the impact to 3.47 billion years. But the new research shows that these cones may have been altered by later events, such as heating or water circulation, making their direct dating less reliable.

That is why geologists now prefer to date minerals that have undergone transformation due to the impact, rather than the cones themselves. Zircon, for example, partially recrystallizes under intense heat, thus recording the age of the impact. This approach allows bypassing secondary alterations and obtaining more precise ages for the oldest impacts.