Culture Online


When was the Earth created?

Thank you for the question.

Small glass sphere on a rock

13 September 2022

The short answer is 4.5 billion years ago – that’s 4500,000,000 years ago! Which is nearly a third of the age of the universe (around 15 billion years). So how do we know this? The answer is a technique called radiometric dating – a method of determining the age of rocks by looking at how one element decays into another. For example, uranium decays into lead - unstable atoms in uranium breakdown and lose energy through radiation; they also lose particles in the form of electrons (beta decay) and helium nuclei (alpha decay). It turns out that this is a very precise process which acts as a universal clock. Using these methods to date rocks is called geochronology. And by looking for the oldest rocks, scientists can narrow down the age of the Earth.

The oldest rock on Earth remains a subject of debate – but it has been suggested that a tiny crystal called a zircon, discovered in rock in Western Australia, is thought to be 4.4 billion years old. However, there is a possibility that there has been radiation damage to these fragments so there is some uncertainty in this age.

cathodoluminescence (an electron beam)

Cathodoluminescence (electron beam) image of a 400-μm Jack Hills zircon.

Another candidate for the oldest rocks comes from Northern Canada called the Nuvvuagittuq Greenstone Belt. This formation of rock, which outcrops on the edge of Hudson Bay, is thought to be up to 4.4 billion years old, although this dating, too, is the subject of debate.

The Nuvvuagittuq greenstone belt Hudson bay Canada

The Nuvvuagittuq Greenstone Belt, Hudson Bay, Canada.

Another contender, with an arguably undisputed age, was found on the moon! The Apollo 14 misson brought back some moon rock samples, and on studying the crystals made up in one rock called Big Bertha, scientists found some minerals that could only have been formed on the Earth. So how did this rock get to the moon? The most likely explanation is that an asteroid hit the Earth and ejected impact material from the Earth into space, some of which ended up on the moon. This was in the very early life of the Earth when there were many such bombardments and when the moon was much closer to the Earth than it is today. 

“Big Bertha” which contains minerals which suggest it must have formed on Earth around 4 billion years ago.

“Big Bertha” which contains minerals which suggest it must have formed on Earth around 4 billion years ago.




Finally, the oldest known rock comes from space in the form of a meteorite called the Murchison meteorite, which is around 7 billion years old – much older than the Earth itself!