In Western Australia there are crystals four thousand four hundred million years old
On a line of low hills eight hundred kilometres north of Perth, a zircon grain was dated at 4,404 million years: the oldest material of terrestrial origin known. It is not a coincidence. Almost nothing has happened to this piece of crust since the beginning.
Almost every landscape we visit is young. The Alps are tens of millions of years old, a volcanic island can be thousands, and even the great canyons were cut a geological sigh ago.
Here the scale is different. You are not looking at an ancient landscape: you are looking at the oldest ground left on the planet's surface, and much of what you will see is explained by that age.
01 Four thousand four hundred and four million
The finding has an impressive precision: 4,404 million years, plus or minus eight. For a sense of scale, the Earth is some 4,540 million years old, so that crystal formed when the planet had existed for barely a hundred million years.
And one detail makes it stranger still. The zircon is not inside the rock it formed in: it is a loose grain, carried by water and deposited in a much younger conglomerate, around three thousand million years old. That is, an extremely ancient pebble inside an old rock.
That is exactly why it survived. Zircon is an extremely hard and chemically indestructible mineral: it withstands erosion, transport and metamorphism, and it locks inside the radioactive clock that allows it to be dated. The parent rock vanished aeons ago; the crystal did not.
02 Crust nobody has recycled
The interesting question is not where the crystal turned up, but why it turned up here. And the answer is that the bulk of this state is two extremely old blocks of crust, the Yilgarn craton and the Pilbara craton.
A craton is a piece of continental crust that stabilised thousands of millions of years ago and has not since been folded, melted or swallowed by a subduction zone. These two are so old that they were already joined in the Archean, forming part of one of the first supercontinents, between three thousand and three thousand two hundred million years ago.
That explains the look of the place better than anything else. There are no young ranges, no volcanoes, no glacial valleys: there is an immense plain, worn down to the root, with low hills that are what remains of extremely ancient mountains. The state's highest point stops at 1,249 metres.
03 And life, almost as old
If the crust has not been recycled, neither has what sat on top of it. In 2017, evidence was published of the oldest known life on land, in 3,480-million-year-old mineral deposits in the northern craton, of the kind that forms around hot springs and geysers.
And the other half of the story is still running today. In a shallow bay on the west coast there are living colonies of micro-organisms that trap sediment and precipitate carbonate, building mounds layer upon layer. It is the same process that left the oldest fossil structures in the record.
What keeps them there is a local quirk: the water in that bay is far saltier than the open sea, and that extreme salinity keeps out the animals that anywhere else would eat them. A geographical accident preserves an archaic ecosystem.
04 The red bands of iron
This article's cover image is a banded iron formation, and it is probably the most beautiful record there is of a planetary change. The bands alternate iron-rich layers with silica layers, millimetre by millimetre, through metres and metres of thickness.
They formed when the iron dissolved in the early oceans met the oxygen that organisms like those in the bay's mounds were beginning to produce. The iron oxidised, became insoluble and settled to the bottom, again and again, in cycles written down as stripes.
And there is the connection to the present: those layers are today the iron ore that sustains much of the state's economy. The red gorges of the interior and the longest ore trains in the world are the same thing seen from two different places.
05 Two and a half million square kilometres
It is worth putting numbers to the scale, because it is not intuitive. The state covers 2,527,013 square kilometres, is the country's largest and has 20,781 kilometres of coastline, of which almost eight thousand belong to islands.
In all of that live some 3,008,700 people, which gives 1.11 per square kilometre. And most of them are concentrated in the far southwest, so the rest of the territory has a density close to empty.
That combination, a territory the size of western Europe with the population of a mid-sized city, is a child of the same thing as the zircon. An ancient craton is flat, dry, without rich soils and without big rivers: an extraordinarily hard place to settle and an extraordinarily good one for preserving things.
06 How to travel it
The first rule is to accept the distances. Between the capital and the inland gorges there are on the order of fifteen hundred kilometres, and between the capital and the far north, over two thousand. This is not improvised with a small car and three days.
The second is to pick one axis and exhaust it, rather than trying to see everything. The west coast axis, going north from the capital, strings together the bay of mounds and the reef; the inland axis leads to the banded iron gorges. The two together are a long month.
And the third is a way of looking. When you stop at a red gorge and see the stripes in the wall, remember that every pair of bands is one cycle of an ocean that did not yet have oxygen. There is no viewpoint on Earth with more time inside the frame.
