NSW - topography and geomorphology
Topography, geomorphology and geomorphic history are usually linked to large, sometimes continental-scale, events. For this reason, the following summary of the major events in the formation of the landscape of NSW has been provided.
"The land masses of the world were once aggregated into a single supercontinent called Pangea. Eventually Pangea separated into two parts, Laurasia to the north and Gondwana to the south. Gondwana comprised South America, Africa, Madagascar, Antarctica, Australia and New Zealand and some now northern lands including India, Turkey and Arabia. Gondwana started to break up into smaller continents about 180 million years ago. Fifty million years ago Australia broke away from Antarctica, severing its last links with the other great lands of Gondwana." (White 1986)
Major events in the formation of the landscape in NSW
NSW contains three main topographical divisions, as follows:
- The Great Dividing Range comprising the Eastern Highlands, the Great Escarpment and the Western Slopes
- The Far West Uplands
- The Western Plains lying in between.
The eastern half of the State comprises thick sequences of sedimentary and metamorphic rocks that were intruded by granites and folded and faulted while the continent was part of Gondwana. Thick piles of less deformed sediments accumulated in the Murray, Sydney and Great Artesian Basins. Subsequently the whole east coast and Great Dividing Range was created by earth movement warping up a gentle arch along the eastern edge of the continent. This was associated with the opening of the Tasman Sea and Southern Ocean during the break-up of Gondwana.
This break-up was accompanied by volcanic activity in some places, and the short steep rivers flowing to the Pacific rapidly eroded the eastern slopes to produce the steep and rugged escarpments and deep gorges that run behind the coast. Geomorphically, the western slopes can be seen as a dissected ramp that links the uplifted highlands with the western plains. The Great Dividing Range is an elevated region of gently undulating country or broad plains, with the exception of areas of dramatic gorge country associated with the Great Escarpment (Packham 1969).
The Western Plains are vast areas of shallow riverine sediment deposited by streams ancestral to the Murray-Murrumbidgee in the Riverina and the Darling and its tributaries in the Darling Riverine Plain. The plains slope gently west from the Great Dividing Range and lie against the eroded bedrock plateau and low ranges of the Cobar Block and the Barrier Ranges. The extensive sand sheets and dunefields of the Murray Basin cover bedrock in the south-western corner of the State.
The Western Plains experienced very little total uplift, but here and there in the Far West Uplands there has been some post-Miocene faulting.
Page last updated: 27 February 2011