In what is now western Australia, but 2.229 billion years ago, catastrophe struck Earth. Literally.
A 7-kilometer-wide asteroid slammed into our planet, within minutes carving out a huge crater 70 kilometers across. It released vast amounts of dangerous chemicals into the atmosphere, creating a secondary catastrophe. The immediate effects of a large impact are legion and obvious, but this second effect was a climatic catastrophe: All those chemicals (like water vapor) warmed the planet. Earth got so much hotter so quickly that the entire surface changed drastically: it melted.
But this was a good thing. At that time, Earth was locked in a global ice age, so when I say "melted" I mean the ice melted, freeing the Earth from its frigid grip.
At least, this is possibly what happened then. But it all comes back to that number, 2.229 billion years. Here's how this happened.
In western Australia, near what is now Meekatharra, is a strange clump of rocks called the Barlangi granophyre (a granophyre is a type of granite). From the air, scientists have mapped the magnetic field of that area, and found a magnetic anomaly about 20x11 km in size. In that area they also found samples ...