The Putangirua Pinnacles (also known colloquially simply as The Pinnacles) are a geological formation and one of New Zealand's best examples of badlandserosion. They consist of a large number of earth pillars or hoodoos located at the head of a valley in the Aorangi Ranges, on the North Island of New Zealand, in the Wairarapa region.
Some 7 to 9 million years ago when sea levels were much higher, the Aorangi ranges were an island and as this landmass was eroded over time, large alluvial fans formed on its southern shores. Within a few million years however, sea levels rose again and this island was submerged also. Since the Ice ages, sea levels have receded and the old alluvial fans have been exposed to the erosive forces of wind and water, which have weathered away the conglomerate. In some places this conglomerate is protected from erosion above by a cap of cemented silt or rock, resulting in the formation of spectacular Pinnacles, many of which have prominent fluting caused by rainwater running down their sides during major storms. It is not known exactly how long the pinnacles have been forming but they are thought to be less than 125,000 years old with major erosion probably beginning 7000 years ago and accelerating in the last 1000 years with the deforestation of the area.