Most of the planet's early crust is gone - melted, buried, or ground to nothing by billions of years of restless tectonics. Barberton is the rare exception, a window onto the Archean Eon that somehow survived. The belt is built from ancient lava flows and seafloor sediments laid down between roughly 3.5 and 3.2 billion years ago, then folded and tilted until they stood on edge where erosion could expose them. The Makhonjwa Mountains make up about 40 percent of the belt and run for more than 113,000 hectares along the border. Because so little has disturbed them, the rocks here preserve an unusually complete record of early surface conditions - the chemistry of ancient seawater, the residue of volcanic eruptions, the faint traces of some of the oldest life known. Their value is so singular that UNESCO inscribed the Makhonjwa Mountains as a World Heritage Site on 2 July 2018, and in 2022 the International Union of Geological Sciences named the belt one of the first 100 geological heritage sites on the planet, a reference point for the whole science of deep time.

One stone here is so distinctive it gave science a new word. Along the Komati River, brothers Morris and Richard Viljoen - then doing doctoral research - found a strange magnesium-rich volcanic rock laced with long, blade-like crystals frozen mid-formation, a pattern geologists call spinifex texture. In 1969 they named it komatiite, after the river. Komatiites are the fingerprints of a hotter young Earth: they erupted at temperatures far above modern lavas, runny as motor oil, pouring from a mantle that has never again been quite so molten. The Komati River still threads through the belt that its name now describes, in mineral, on every geology syllabus in the world.

Among the layered cherts, researchers have read the record of catastrophe. Around 3.26 billion years ago, a meteorite struck - one geologists call S2, estimated at tens of kilometres across, dwarfing the asteroid that would later end the dinosaurs. A 2024 study led by Harvard geologist Nadja Drabon, working from Barberton's rocks, reconstructed the aftermath: a tsunami that tore up the seafloor, an impact so violent it may have brought the upper oceans to a boil. Yet the story has a twist. The same blast appears to have flooded the seas with iron and phosphorus, the raw nutrients of life - and in the layers just above, the microbes came surging back. Destruction, here, looks a great deal like fertilizer.

This is not a tame landscape. The belt is no formal national park, yet it sits in big-game country, and field expeditions venture in accompanied by armed rangers - protection not against people but against the rhinos and elephants that share the hills. The setting suits the subject. There is something fitting about reaching some of the planet's oldest rock through wild African bush, past creatures that are themselves the product of three and a half billion years of the experiment that began, in part, right here. The belt takes its name from the nearby town of Barberton, a gold-mining settlement in Mpumalanga, and gold still threads through these ancient rocks - the same mineralisation that first drew prospectors now sits beside the world's oldest stories of life, in a shallow Archean sea turned to stone and lifted into the Mpumalanga sky.