Australia: The Land Where Time Began

A biography of the Australian continent 

The Australian Alps, part of the Great Dividing Range, are a series of high plateaux, that curve from a short distance north of Kiandra in New South Wales to Mt Buller in Victoria. On a world scale they low, but they are the highest ranges in Australia, with Mt Kosciusko as the highest point in Australia at 2228 m. The highest peaks on the range are in the middle of the arc-shaped , 120 km main ridge. Lower rugged mountains surround the main ridge. The Snowy Mountains are on the northern end of the arc, where Mt Kosciusko and a few other mountains reach above 2000 m. Victoria's highest mountains, Mt Bogong (1986 m), Mt Feathertop (1922 m) and Mt Hotham (1959 m), form the southern end of the arc. Mt Buffalo, a massive horst (a block mountain), is isolated from the main range and is lower, 1723 m, all sides of which are steep-sided faults.

The geology of the Alps is very complicated, a number of different rock types being involved in their formation. Some of the rock types involved are granites, basalt, schists, limestone. The rocks of the present ranges are mere remnants of a much larger mountain range that formed about 500 Ma, subsequently being eroded down to a near level plain. The present ranges resulted from the remnant rocks being uplifted, together with the rest of the east coast of the continent, about 2-3 Ma, during the Kosciusko Uplift. At this time there was a lot of folding and faulting that produced the north-south trending ranges, separated by rift valleys that are almost parallel. The region of Mt Kosciusko was the part of the range that underwent the greatest uplift, ranges in the area attaining heights of about 3000 m.

The uplift over wide areas had big effects on the drainage of the catchments affected. The rivers that previously flowed to the east were diverted inland, forming what is now the Murray-Darling system. Rivers that continued flowing to the sea where shorted and of greater power after the uplift, flowing down the steepened eastern slopes of the Alps. Weathering and erosion have since lowered the Alps to their present elevation. Between Mt Kosciusko and Mt Twynam (2196 m), an area of about 50 sq km was the only place on the Australian mainland that was glaciated during the Pleistocene ice age, about 30,000-15,000 years ago.

These glaciers were much smaller than those of Tasmania, the longest being about 20 km long in the upper valley of the Snowy River. There are a number of small lakes and cirques near the top of the plateau, that are evidence of the glaciation that occurred there. At the foot of Mt Twynam is Blue Lake, the largest of these lakes. To the south are 4 lakes, Hedley Tarn, Club Lake, Lake Albina and Lake Cootapatamba. There are also the remains of what used to be 2 moraine dams in small valleys that later drained. Throughout the Alps are large piles of smooth boulders that were polished by ice and snow.

Sources & Further reading

1. Helen Grasswill & Reg Morrison, Australia, a Timeless Grandeur, Lansdowne, 1981

Ranges