The 350-Million-Year-Old Domes That Wear a Living Skin

In the remote Kimberley region of Western Australia, 350-million-year-old sandstone has been carved into a maze of beehive-shaped domes, each one banded in orange and black like a tiger's flank. The Bungle Bungle Range rises three hundred metres above the surrounding plain, but its most remarkable feature is not the rock itself—it is the living skin that coats its surface.

A Devonian River, Now Stone

The sandstone that forms the Bungle Bungles was laid down 350 to 360 million years ago during the Devonian Period. A massive river system carried quartz sand and pebbles from the north and deposited them in a broad alluvial fan, creating the cross-bedded sandstone and conglomerate that make up the range today.

The sediment was buried, compacted, and cemented into rock. Then, over millions of years, the entire region was uplifted. Water and wind began to carve the sandstone along its natural fractures—joints and faults that guided the erosion into a labyrinth of narrow gorges and rounded peaks.

The result is not a single mountain but a field of hundreds of domes, each one shaped by the same slow process. The domes are not random. Their pattern follows the network of joints in the rock, like a city laid out along its streets.

The Cyanobacterial Stripes

The orange and black bands that give the Bungle Bungles their iconic appearance are not layers in the rock itself. They are a surface phenomenon, a living coating applied from the outside.

The orange bands are dry sandstone, where iron oxide minerals have been oxidised by sun and air. The dark grey-black bands are colonies of cyanobacteria—single-celled photosynthetic organisms that have been on Earth for at least three billion years. These microbes grow where moisture lingers, usually along bedding planes and joints where water seeps out after rain.

The cyanobacteria bind sand grains together with a sticky sheath of polysaccharides, protecting the rock beneath them from erosion. The orange bands, lacking this protective coating, erode more quickly. This differential erosion maintains the domes' shape: the black bands hold the rock in place while the orange bands recede, deepening the stripes with every wet season.

The domes are not static. They are being carved and recoloured in real time, by the same kind of organisms that built Earth's first reefs.

A Landscape in Slow Motion

The Bungle Bungle Range is eroding at a rate of roughly one millimetre per year. At this pace, the entire range will be worn flat in about three hundred thousand years—a blink in geological time. But for now, the cyanobacteria continue their slow work, painting and protecting the sandstone in equal measure.

The range was unknown to most Australians until 1983, when a documentary film crew flying over the Kimberley noticed the striped domes from the air. Today the area is protected as Purnululu National Park, a UNESCO World Heritage site.

The Bungle Bungles are a reminder that geology is never finished. The rock is still being shaped, still being coloured, still alive with microbes that have been doing this work since before the continents existed.