Turquoise colour
From November.
S5A-0043 — CC BY 4.0 · Mike Lehmann, Mike Switzerland 23:22, 24 February 2007 (UTC) — CC BY-SA 3.0 · Dietmar Rabich — CC BY-SA 4.0 · Dietmar Rabich — CC BY-SA 4.0 · Chuq — CC BY-SA 4.0
Blue Lake is a crater lake in a dormant volcano near the city of Mount Gambier in the Limestone Coast region of South Australia, about 2 km south of the city centre in a straight line. The Boandik people call it Warwar, meaning crow country. The volcano once held four crater lakes, but only two remain after the water table dropped. Estimates of the last eruption range from about 4,300 to 28,000 years ago; if the youngest is right, it may be the most recent volcanic eruption on the Australian mainland. The lake averages about 72 metres deep and measures about 1,087 by 657 metres, its surface lies below the level of the city's main street, and it supplies Mount Gambier with drinking water. It is best known for its colour change: each November the water turns a vivid deep turquoise, then gradually returns to a duller blue in late February to March. Scientists think the cause is the summer warming of the lake's upper layer. Green crater walls surround the water. A 3.6 km road and walking track runs around the lake, with many viewing points. The water itself is off limits to visitors, as the lake is the city's drinking supply. The best time to visit is from December to February.
From November.
Green slopes.
3.6 km.
Mount Gambier, South Australia, Australia
November to March.
No, it is the city's drinking water supply.