Mt Toolbrunup, Stirling Range NP (Top trail)

Stirling Range is also known by its Aboriginal name - Koi Kyenunu-ruff – meaning ‘misty mountains’, owing to the unusual cloud formations that often wreath the higher peaks. 

Koi Kyenunu-ruff is part of the traditional country of the Menang and Goreng Noongar people, but the ranges have different meanings to each group. 

The Menang and Goreng Noongar people have lived in and around the mountains for thousands of years. The surrounding plains and valleys provided important food resources, with women gathering roots, seeds and fruits while men hunted kangaroos, wallabies and other native animals.

Traditionally, Noongar families moved seasonally through the landscape, building small shelters and adapting to the cooler mountain climate by wearing kangaroo skin cloaks.

Following European settlement, much of the surrounding land was cleared for farming and grazing and families were displaced from much of their traditional land. Despite this, Noongar people have maintained strong cultural connections to the Stirling Range, which remains a place of ongoing cultural and spiritual significance today.

Aboriginal cultural content on this page has been developed with information sourced from Department of Biodiversity, Conservation and Attractions’ publications. It may not represent all knowledge or perspectives of Aboriginal people. 

Rising dramatically above the plains of Western Australia’s Great Southern region, Koi Kyenunu-ruff (the Stirling Range) is one of the most distinctive mountain landscapes in Australia. For visitors today, the trails within the range offer more than spectacular views and challenging hikes. Every cliff face, rocky summit and folded ridgeline is part of a geological history stretching back hundreds of millions of years.

Remnants of an Ancient Sea

Koi Kyenunu-ruff owes its existence to immense tectonic forces that shaped the southern edge of Australia. When the supercontinent – Gondwana – broke apart into what is now Australia and Antarctica, a valley developed. As this low point developed, many layers of sedimentary rock were pushed ‘up’ to form a series of hills and mountains known as ‘rift shoulders’.

The range sits on the southern margin of the Yilgarn Craton — one of the oldest pieces of continental crust on Earth. South of the range lies the Albany–Fraser Orogen, a vast belt of deformed rocks formed between 1,200 and 1,400 million years ago.

Unlike the nearby Porongurup Range, which is made of granite, Koi Kyenunu-ruff is composed mainly of ancient sedimentary rocks including sandstone and shale. These sediments were originally laid down in the coastal shallows of an ancient sea, likely in a river delta environment. Over time, the sediments were buried, compressed and altered into the hard rocks seen today. 

Evidence of this ancient environment can still be found throughout the range. Ripple marks and bedding layers preserved in the rocks reveal the movement of water and sediment long before the mountains existed. 

Evolution of Koi Kyenunu-ruff 

The rocks of Koi Kyenunu-ruff have attracted scientific interest for many years. The Stirling Range Formation is now generally understood to be around 2.0 to 1.8 billion years old, preserving evidence of an ancient shoreline environment shaped by storms, longshore currents and tidal currents.

Fossil-like impressions found in the rocks have been compared with ancient jellyfish-like forms, but their age and interpretation have been the subject of scientific debate. These findings continue to reshape scientific understanding of the range’s deep geological history.

If we fast forward to around 55 million years ago, during the Eocene period, when sea levels were much higher than present levels, the peaks of Koi Kyenunu-ruff may have resembled a small archipelago. At that time, the shoreline extended close to the southern edge of the range.

Soils, Water and the Landscape

The geology of Koi Kyenunu-ruff strongly influences its soils, vegetation and walking experience. Along many slopes, a layer of clay-rich soil slows the movement of water through the ground. These moist conditions can favour the spread of Phytophthora dieback disease, one of the park’s major environmental threats.

The most developed soils occur on valley floors where water collects and conditions are more fertile. This variation in soils and moisture creates a remarkable diversity of plant communities across the park, contributing to the Stirling Range’s reputation as one of Western Australia’s biodiversity hotspots.