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The Blue Lake - A glacial cirque banner

The Blue Lake - A glacial cirque
Note the rocky cliff on left side of lake. This is where the glacier scraped rock from the wall before moving it down-hill and depositing it at the melt point at Helms Moraine and Headley Tarn
Headley Tarn
Quartz rich fluids fill joints and cracks in granite, this rock is located on the path to the Blue Lake

The Blue Lake - A Glacial Cirque - Kosciuszko National Park

Latitude -36.404429, Longitude 148.314657

Located in the Snowy Mountains Region of NSW, nearest town Thredbo

Source: modified with permission: www.australianalps.environment.gov.au/learn/geology.html

Source: www.environment.nsw.gov.au/resources/nature/KNPPOM.pdf

Link to Detailed Map

The Blue Lake is located on the main range in Kosciuszko National Park. In 1996 the areas biological significance was recognised when a 320 ha area, comprising the lake and its surrounds and including nearby Hedley Tarn, was designated Ramsar Site 800 under the Ramsar Convention on wetlands. Here we recognise its geological significance as one of only four cirque lakes on mainland Australia.

The Australian Alps

The last major geological event that shaped the Australian Alps was the Great Ice Age, which ended about 10,000 years ago, although glaciation (the covering of the land by permanent ice) was not extensive in the Australian Alps - evidence of it is restricted to the southeast facing slopes above approximately 1500 metres on the main range of Kosciuszko National Park. A large number of landscape features in this area were formed by the effects of the ice lying on, and moving over, the land.

Cirque Lakes

Features such as cirque lakes and moraines are formed by glaciers. Cirques are formed at the head of a glacier on the highest, most sheltered mountain faces, when the glacier digs out a semicircular basin as it pushes down the slope. These basins may later fill with water when the glaciers recede, forming a cirque lake. Blue Lake, Lake Cootapatamba, Albina Lake and Club Lake are the only cirque lakes on mainland Australia. The largest of these is Blue Lake, which is 16 hectares in area and 28 metres deep and it boasts the freshest water in mainland Australia due to its low salt content.

Moraines

Moraines are ridges of ground up rock and other debris dumped along the sides or the tongue of a melting glacier. Sometimes these moraines act as natural dams in valleys by forming moraine deposits. An example of this is Headley Tarn, which is located below Blue Lake. In the image, note the dam wall made of stones dropped by the glacier at a melt point. This type of deposit is known as a terminal moraine. Helms Moraine near Blue Lake is a particularly clear example of glacial transport of one kind of rock onto another.

Helms Moraine is located on the extreme right of the photo of Blue Lake.

The effects of the ice age on the landscape

While ice lay upon on only a small part of the Alps, the effects of the ice age on the landscape were widespread. Periglacial (literally meaning "around a glacier") landscape features such a terracing (caused by the mass movement of ice-and-water saturated soil down-slope), frost-shattered boulders, and block streams ("rivers" of boulders) are all the product of low temperatures, frequent frosts, and persistent snow, and can be found throughout the higher elevations of the Australian Alps.

Getting There

The easiest access point to Blue Lake is from Charlotte Pass where you can park your car. There are toilets here but there are none on the track itself. The return walk via the Main Range Track is 9.3 kilometres and takes about four hours. You need to be relatively fit as there are long uphill stretches. In the first part of the walk you will descend from Charlotte Pass and then cross the Snowy River. There are stepping stones over the Snowy River; if the water is over the stepping stones, this walk is not recommended. Download the Kosciuszko Visitor Guide from www.environment.nsw.gov.au as it has information which may be useful when exploring this region.


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