The Organ Pipes, Victoria

The Organ Pipes are a set of vertical, closely packed basalt columns in the Organ Pipes National Park near Sydenham, Victoria, Australia, formed around one million years ago when lava from a nearby volcanic vent flowed into the valley of Jacksons Creek and pooled to a considerable depth. As the thick lava mass cooled slowly and evenly from the surface inward, it contracted and cracked into a dense array of roughly hexagonal columns up to 20 meters tall, later exposed in cross-section on a cliff face by the erosive action of the creek cutting down through the surrounding rock. The formation is regarded as one of the finest examples of columnar basalt jointing in Australia.