Places I've been: Blue Lake, Mount Gambier, South Australia

 

The most recent field camp took me to the Mt Gambier marr complex along the limestone coast. Mt Gambier's marr complex consists of four (or more) craters, two of which are now above the water table. The largest, Blue Lake, is approximately 70m deep and houses the towns water supply. The local aquifer is composed of limestone, and needless to say, the local population has a minor calcite scale issue inside their pipes. During Summer, the Blue Lake turns a vibrant blue as the warmer water contains more micro-crystals of calcite which reflect the blue wavelength. Mt Gambier is part of the Australia's Newer Volcanics which extends from Mt Gambier to the CBD of Melbourne. The Newer Volcanics is composed of 437 volcanoes (the awesome Dr Julie Boyce counted them!) and the most recently dated eruption is Mt Shank, about 10 minutes south of Mt Gambier.

 

As I as there after summer, the water had returned to it's typical slate blue/grey colour.

 

I've always wondered if this is a fault where you can see the offset between the limestone, basalt and ash layers. This may also be an optical illusion created by a cove. Someday I'll get to the other side of the lake and check it out.