Blue Lake Cirque EarthCache

Blue Lake is located on the main range in Kosciuszko National Park. It is of geological significance as being one of only four cirque lakes on mainland Australia.

The first time I visited Blue Lake many years ago, it was an unforgettable experience. The wildflowers beside the path, crossing the Snowy River, the long walk up, and then the final descent towards Blue Lake. Superb. I have been lucky enough to visit the lake on sunny days when the water is at its bluest.

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 seen on 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 and 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 boasts the freshest water on 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. Helm's moraine near Blue Lake is a particularly clear example of glacial transport of one kind of rock onto another.

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 along the Main Range Track 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 3 hours. You need to be relatively fit as there are long uphill stretches. Most of the track is either paved or with a gravel surface. 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.

Your Task

Use the information above and at the lake (including WP1 Information board) to answer the following questions. Send me your answers via a message for approval prior to logging your find here.

1 What is the largest cirque lake in Australia?

2 What are cirque lakes formed by?

3 What substance are glacial lakes low in?

4 What is the name of the lateral moraine to the right of Blue Lake?

5 Look at the colour of the rocks just above the back of the lake (to your left, below Mt Twynam). Compare with the colour of the rocks beside the track.

6 The colour of Blue Lake can change depending on the weather conditions, cloud cover, etc. What colour is the lake today on your visit?

* Upload a photo of yourself and the lake from the viewing platform.

First to Find - SmudgeyCat - Congratulations!