The area contains thousands of weathered limestone pillars. Some of the tallest pinnacles reach heights of up to 3.5m above the yellow sand base. The different types of formations include ones which are much taller than they are wide and resemble columns—suggesting the name of Pinnacles—while others are only a meter or so in height and width resembling short tombstones. A cross-bedding structure can be observed in many pinnacles where the angle of deposited sand changed suddenly due to changes in prevailing winds during formation of the limestone beds. Pinnacles with tops similar to mushrooms are created when the calcrete capping is harder than the limestone layer below it. The relatively softer lower layers weather and erode at a faster rate than the top layer leaving behind more material at the top of the pinnacle.

(source: wikipedia)