The Devil's Marbles Conservation Reserve contains formations of naturally rounded and oval boulders and is located near Wauchope which is 114km south of Tennant Creek in Australia's Northern Territory. The boulders are located in a traditional aboriginal sacred site and are important to the local tribe. The Arrernte people believe that the boulders are the eggs of the rainbow serpent. Over time, the ceremonies and stories related to the Devil's Marbles have largely been lost, but the site is still very important to the tribe.

The Reserve is accessible all year round and has a network of pathways with information boards and a basic camping area.

Geology and weathering

The remarkable geological formations have been formed by spheroidal weathering. Signs along the pathways describe how the boulders were formed by a combination of mechanical weathering (which cracked the rocks) and chemical weathering (which flaked the surface off).

The boulders were originally part of a solid mass of coarse grained granite which formed deep within the earth's surface about 1640 million years ago. Erosion has since stripped away the overlying material, and weathering processes have shaped them into the "marbles" as they appear now. As the molten magma cooled and hardened to form granite the mass shrank and cracked and these cracks known as joints effectively split the granite body into a series of tight fitting blocks.

The temperature ranges in the Northern Territory outback range from sub-zero temperatures at night to over 40°C during the day - meaning that the erosive processes are still very much at work and the boulders continue to evolve into new shapes.

Controversy

One of the marbles was removed from a formation in 1953 and taken to Alice Springs to form a permanent memorial to John Flynn, the founder of the Royal Flying Doctor Service in Australia. At the time, this was seen as a way of remembering his link to the outback, but in later decades it was a source of great controversy because the rock was removed from a sacred site without the direct permission of the tribal elders. In the late 1990s, a boulder swap was arranged, and the missing marble was removed from the grave, cleaned, and returned to its original place. The grave is now marked with a similar boulder donated by the local Arrernte people.

External links

• Controversy about removing a "marble"
• Devil's Marbles Conservation Reserve