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At 2.2 Billion Years Old, This is the Oldest Impact Crater on Earth


An artists rendering of an impact crater covered in ice. Shutterstock.
Around 2.2 billion years ago, a massive space rock collided against our planet leaving a massive scar. Around 200 million years older than any other site like it on the surface of the planet, the so-called Yarrabubba impact structure is located in Australia. Although the impact site is the oldest found to date, finding it was not easy.

The surface of our planet is continually changing due to tectonic activity and erosion, which makes it very difficult to date very old impact craters. This is precisely the case of the 70 km-wide Yarrabubba crater in Western Australia, which lacked a precise age but was nonetheless considered one of the oldest on our planet.

In a study published on January 21, in Nature Communications, the researchers revealed studying the massive impact site. Although today not much of it is visible, that what lies inside it is what holds invaluable information about the crater and its age. At the center of the impact crater is a small, red hill dubbed Barlangi Hill.

A view of the Yarrabubba impact crater: Image Credit: The Conversation.
A view of the Yarrabubba impact crater

“[Barlangi Hill] has been interpreted as an impact-generated melt rock,” the researchers wrote in the study.

The researchers analyzed minerals crystallized by the impact. They performed an isotopic analysis – to understand the chemical reactions – of the zircon and monazite minerals in order to obtain the precise age. Consequently, using a technique called uranium-lead dating, the scientists discovered that the Yarrabubba impact crater is 200 million years older than the next oldest recognized impact crater, the Vredefort crater in South Africa.

If the dating of the impact crater is accurate, it means that the collision of the massive space rocks coincides with the end of a prehistoric ice age when most of our planet was frozen. The researchers created a number of models that allowed them to study the possible effects of a massive asteroid impact, and the possible effects it would have on an ice sheet, and how it would modify the climate of the planet.

If an asteroid really did impact a continent ice sheet, it kicked up massive amounts of rock, ash, dust, similar to a volcanic eruption. Computer simulations have shown that an impact like that would have spread between 87 trillion and 5,000 trillion kilograms of water vapor into the planet’s atmosphere. This most likely caused the ice sheet to melt, since water is an efficient greenhouse gas.

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