Life below the surface: The legacy of an ancient sea lives on in Chillagoe’s thriving caves



Drive 210km west of Cairns, crossing the fertile plateau known as the Atherton Tablelands, and you will discover the tiny former gold-mining town of Chillagoe, Queensland. Four hundred million years ago, this same region was submerged in an ancient sea, where coral reefs and marine life flourished. Now, this vanished world lives on in the clues left by an extraordinary system of limestone caves hidden just below Chillagoe’s surface.

A daylight chamber inside the Royal Arch Cave, named for Queen Victoria during her reign in 1888. These limestone caves were formed from the hard bodies and shells of marine life, and the walls are filled with fossils. The sunlight in this chamber allows plants to thrive even in this rocky underground landscape.

A ring-tailed gecko (Cyrtodactylus mcdonaldi) living in the rocks around the surface of the caves. These geckoes shelter in crevices and emerge at night to hunt invertebrates. The Chillagoe caves are warm all year round, supporting an incredible level of biodiversity both inside the caves and around the openings.

A karst window in the Fig Tree Chamber in the Royal Arch Cave. Acidic rainwater has dissolved the limestone and created this jagged opening, through which fig tree roots have grown deep into the cave. The rock around features like this is razor sharp; a hazard to unwary tourists.

Cave coralloid in the Pompeii Cave. These formations are common throughout the well-ventilated Chillagoe cave systems, where evaporation leaves  popcorn-like mineral deposits behind. While coralloids should not be mistaken for actual fossilised coral found in the caves, the formations do seem to call up images of the long dead coral reefs that once occupied their place.

Cave huntsman spiders (Yiinthi chillagoe) are common throughout the caves. Torch beams catching their reflective eye-shine often reveal a wall of glittering green jewels. These spiders are enormous, with a 13cm leg span, but are totally harmless to people. They thrive on the crickets, moths and cockroaches abundant in the caves.

An inactive stalagmite in the Pompeii Cave. This low section of the cave is covered by a false floor, formed when flowing water deposited minerals over a sediment which then eroded away. The remaining formations often appear to defy gravity.

 A roost of common bent-wing bats (Miniopterus schreibersii), consisting of large ginger adults and wrinkly pups. These microbats live and breed in caves where they hunt insects by echolocation. Snakes such as the spotted python (Antaresia maculosa) commonly make their way into the cave systems to feed on the many microbat species in Chillagoe.

The Picnic Chamber in the Royal Arch Cave appears to be melting due to the high number of speleothems (formations). Sunlight pours into this chamber from various karst windows, feeding algae and other photosynthesising organisms which give the formations a green-grey tinge.

These stalactites have broken off and begun to regrow giving them the appearance of upside-down candles. Stalactite formation begins through these thin, hollow straws, which eventually become blocked and expand