Geological History of Cradle Mountain

Cradle Mountain-Lake St. Clair National Park is a treasure trove of geological history, showcasing evidence of not just one, but three distinct glacial stages that occurred over the past two million years. This remarkable layering of glacial activity has left an indelible mark on the landscape, creating the rugged, craggy peaks and valleys that define the region.

Now protected within the Tasmanian Wilderness World Heritage Area, Cradle Mountain was formed millions of years ago when an igneous dolerite sill - a thick, horizontal sheet of volcanic rock - intruded into the region’s existing Permian-Jurassic sedimentary layers. As this molten rock cooled and solidified over time, it created a broad, hard layer that would eventually become the foundation of Cradle Mountain.

During the Pleistocene epoch, successive waves of glaciation swept across the landscape, carving and sculpting the terrain. The relentless grinding and scouring of the glacial ice left dramatic caps of dolerite rock atop Cradle Mountain and the surrounding peaks, including Mt. Ossa, Tasmania's highest mountain at 1,617 metres.

Cradle Mountain earned its name from its distinctive shape, which resembles the contours of a miner's cradle - a tool used for sifting gold from river sediment. It features four distinct summits that have been named and measured - each representing a unique chapter in the mountain’s geological story. The tallest of these is Cradle Mountain itself, standing proud at 1,545 metres, followed by Smithies Peak (1,527 metres), Weindorfers Tower (1,459 metres) and Little Horn (1,355 metres).

The mountain's dramatic glacial history is evident in the U-shaped valleys and cirque lakes that dot the landscape, formed over millions of years by the relentless grinding of ice. Most significant of these is Lake St Clair - Australia's deepest natural freshwater lake at 167 metres - carved out by the powerful glacial processes that have sculpted this ancient terrain.

Cradle Mountain-Lake St. Clair National Park comprises a diverse array of rock types, from the Jurassic dolerite that forms the jagged peaks of Mt. Ossa to the metamorphic and sedimentary layers that underpin the region's soils and support its unique flora and fauna. This biodiversity is on full display within the protected area, which was granted UNESCO World Heritage status in 1982 in recognition of its outstanding natural values. Among the park's many wonders is the rare Nothofagus gunnii tree, the only cold-climate, winter-deciduous tree in the world.