The Tasmanian Wilderness World Heritage Area (WHA) conserves a profusion of complex and well-exposed geological features and the most significant and extensive glacially modified landscapes in Australia. The area contains Australia's greatest array of landscapes and geological types, including rocks from all but one geological period. These underlie a great diversity of soil types of high conservation value. Indeed, the WHA incorporates the most extensive peatlands in the southern hemisphere. The WHA is an area affected by the most diverse landforming processes in Australia -- processes which have resulted in a landscape of tremendous beauty. The Tasmanian wilderness is renowned as a region of dramatic mountain peaks, deep river valleys, spectacular gorges and wild and pristine rivers that twist their way through the wilderness.
The WHA is renowned for its mountain beauty
(Photo by Steve Johnson)
An evolving landscape
The dramatic landscapes of the Tasmanian Wilderness World Heritage Area reveal rich insights into the forces that have shaped, and continue to shape, the Earth's surface. The oldest rocks date back to the Precambrian period, over one billion years ago. Such rock types -- for example, quartzites and quartz schists -- form some of the most spectacular mountains of the WHA, such as the shining white half-dome of Frenchmans Cap.
Sandstones, siltstones and conglomerates, dating back to the Cambrian and Ordovician periods contain a variety of ancient marine fossils. These reveal a legacy from a distant past when what we now call Tasmania was beneath a shallow, tropical sea.
Permian and Triassic sedimentary rocks and fossil assemblages resemble similar deposits on other continents and provide evidence for the existence of the supercontinent, Gondwana. The landscape reveals features associated with the separation of the Australian and Antarctic plates during the latter stages of the break-up of Gondwana. During the Jurassic, some 170 million years ago, tectonic activity associated with the fragmentation of Gondwana and subsequent faulting laid the foundations of the dolerite mountains typical of much of the WHA. The final stages of the break up of Gondwana during the Tertiary resulted in further widespread faulting producing a landscape very similar to that occurring today.
A land carved by glaciers
Glacially carved lake
(Photography by Steve Johnson)
The beautiful, rugged mountain landscapes so characteristic of the Tasmanian Wilderness are largely the legacy of at least three major glaciations during the Pleistocene (2 million-10 000 years ago). Thousands of highland lakes and tarns, cirques and U-shaped valleys have been carved by the massive erosional force of glaciers.
Depositional features such as outwash gravels and moraines which hold back the waters of lakes are typical features of the landscape. Huge boulders known as erratics which have been carried by glaciers far from their parent rock sit incongruously upon the landscape, testimony to the power of these rivers of ice.
Fluctuating sea levels during the glaciations also provided conditions for the development of a wide range of coastal features including a diverse suite of coastal dunes.
The world of caves
Extensive areas of limestone, in places up to two km thick, and considered to be the best developed of its kind in the world, are a major feature of the WHA. The chemical weathering of this limestone has led to a profusion of extensive cave systems. Some of the largest and deepest caves in Australia are found in the region. Some are globally significant Aboriginal sites which have revealed some of the richest deposits in Australia. Other caves, such as Marakoopa Cave, reveal formations of great beauty.