These amazing natural limestone structures were formed approximately 25,000 to 30,000 years ago, after the sea receded and left deposits of sea shells. Over time, coastal winds removed the surrounding sand, leaving the pillars exposed to the elements.
Although the formation of the Pinnacles would have taken many thousands of years, they were probably only exposed in quite recent times. Aboriginal artifacts 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.
The Pinnacles remained unknown to most Australians until the 1960s, when the area was added to Nambung National Park. Today it receives over 250,000 visitors a year.
The best season to see the Pinnacles is spring from August to October, as the days are mild and wildflowers start to bloom. The pinnacle formations are best viewed in the early morning or late afternoon as the play of light brings out the colors and the extended shadows of the formations delivers a contrast that brings out their features.
Source
