From seabed to sunlight
The jagged, mushroom-shaped islands of the Waigeo karst labyrinth are the fossilized remains of an ancient marine ecosystem. During the Miocene Epoch, between 5.3 and 23 million years ago, this entire region was a shallow tropical sea. In these warm, sunlit waters, extensive coral reefs flourished, supporting a high diversity of marine life. The skeletons of countless generations of corals and other marine organisms, all made of calcium carbonate, accumulated on the seafloor, gradually compacting into thick layers of limestone.
Tectonic forces associated with the collision of the Pacific and Australian plates then began a slow but powerful process of uplift, lifting this ancient seabed far above sea level. Once exposed to the elements, the limestone began to dissolve. Rainwater, made slightly acidic by absorbing carbon dioxide from the atmosphere and soil, infiltrated cracks and fissures in the rock. This weak carbonic acid relentlessly dissolved the limestone, a geological process known as karstification. Over millennia, this process sculpted the dramatic landscape seen today, carving the rock into steep-sided islands, sinkholes, and underwater caves. The distinctive mushroom shape of many islands comes from erosion by waves and bioerosion from marine organisms at sea level, undercutting the harder rock above.