The Pinnacles

Nambung National Park
Western Australia

The formation of these pinnacles is quite fascinating. Keep in mind, this is just one photo. The area they cover is huge and there must be thousands of them, upwards of 15-20 feet high.

I can't remember exactly how they are formed, but it goes a little something like this... Over the years the sand in this area would get wet. As the moisture seeped down it would bond the sand together. When the remaining sand in the area blew away, these huge pinnacles were left standing.

One of the years, Sports Illustrated shot some of their swimsuit issue here. If anyone has a pic, send it to me so I can post it here.

If anyone knows the exact process of formation, email me. <--- You know I've been asking this since 1996, and only now, October 1999 that I actually get an answer from someone! Special thanks go to Mike and Joanne Winslade of Perth for sending me this text, taken from http://www.calm.wa.gov.au/national_parks/previous_parks_month/nambung.html

In the Pinnacles Desert, right in the heart of Nambung National Park, thousands of huge limestone pillars rise out of a stark landscape of yellow sand. In places they reach up to three and a half metres tall. Some are jagged, sharp-edged columns, rising to a point; while others resemble tombstones.

The raw material for the limestone of the pinnacles came from sea shells in an earlier epoch rich in marine life. These shells were broken down into lime-rich sands which were brought ashore by waves and then carried inland by the wind to form high, mobile dunes. Three old systems of sand dunes run parallel to the WA coast, marking ancient shorelines.

The oldest of these, known as the Spearwood dune system, is characterised by yellow or brownish sands. In winter, rain, which is slightly acidic, dissolves small amounts of calcium carbonate as it percolates down through the sand. As the dune dries out during summer, this is precipitated as a cement around grains of sand in the lower levels of the dunes, binding them together and eventually producing a hard limestone rock, known as Tamala Limestone.

At the same time, vegetation that became established on the surface, aided this process. Plant roots stabilised the surface, and encouraged a more acidic layer of soil and humus (containing decayed plant and animal matter) to develop over the remaining quartz sand.

The acidic soil accelerated the leaching process, and a hard layer of calcrete formed over the softer limestone below. Cracks which formed in the calcrete layer were exploited by plant roots. When water seeped down along these channels, the softer limestone beneath was slowly leached away and the channels gradually filled with quartz sand. This subsurface erosion continued until only the most resilient columns remained. The Pinnacles, then, are the eroded remnants of the formerly thick bed of limestone.

As bush fires denuded the higher areas, south-westerly winds carried away the loose quartz sands and left these limestone pillars standing up to three and a half metres high.

Although the formation of the Pinnacles would have taken many thousands of years, they were probably only exposed in quite recent times. Aboriginal artefacts at least 6,000 years old have been found in the Pinnacles Desert despite no recent evidence of Aboriginal occupation. This tends to suggest that the Pinnacles were exposed about 6,000 years ago and then covered up by shifting sands, before being exposed again in the last few hundred years. This process can be seen in action today - with the predominantly southerly winds uncovering pinnacles in the northern part of the Pinnacles Desert but covering those in the south. Over time, the limestone spires will no doubt be covered again by other sand drifts and the cycle repeated, creating weird and wonderful shapes over and over again.