Last weekend Jim and I ventured across to South Australia and my home town of Mt Gambier to wish my grandmother a happy 97th birthday. It was wonderful to see her looking much perkier than during our last visit. Although a bit worn out, she’s not doing too badly for her age and I hope to have her around a few more years yet.

Mt Gambier is famous for its Blue Lake, which formed in one of the craters left behind after the site’s original volcano exploded and collapsed. In the winter the lake is a very dull shade of grey, but come summer it turns an extraordinary electric blue, a colour that has to be seen to be believed.

Right now, the lake is just on the turn. In a few weeks it’ll be amazing tourists and locals with its vibrant blue-ness, and will stay that way until around March.

This is what it looked like on Saturday.

And this is what it will look like come summer. I know it looks quite bright but, believe me, this photo doesn’t do justice to the colour. It’s extraordinary!

Though there’s been great argument over the years as to why the lake changes colour, scientific consensus seems to lean toward warming of the lake surface as the cause, which results in the formation of calcite crystals. As the temperature rises, more crystals precipitate out, removing humic substances from the water and scattering more blue light toward the surface. Or something like that. I’m okay with the bio-chemical bit but my brain starts to hurt at the first mention of light absorption and refraction. If you’re after a proper explanation the geology section of Mt Gambier’s tourism website is fairly comprehensive.


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