Daily Photo – The Impressive Colours of Lake Tekapo

Here’s a statistic for you: Lake Tekapo is roughly 83 square kilometres in size. I know this because I read it. Although I can’t remember where. While I was checking to see if this was correct, I also discovered that it sits at an elevation of approximately 710 metres above sea level and reaches a depth of close to 120 metres. Although that is not what it is most famous for, its most legendary feature is the famous turquoise-blue water. This is thanks to the nearby Southern Alps.

You see, the Southern Alps are not merely a nice decorative backdrop; they are also remarkably useful. High above the Mackenzie Basin, a number of glaciers perform a slow-motion demolition, grinding the local schist into a powder so fine it makes talcum powder look like gravel. This is what geologists refer to as “glacial flour.”

When summer hits, the meltwater flows into the lake, carrying with it billions of particles of this glacial flour. Along the way, these particles remain suspended in the water until it reaches the lake. Then physics takes over. These suspended particles absorb the drab, boring, sensible colours of the spectrum and scatter colourful blues and greens with great neon enthusiasm. The result is a body of water that looks less like a natural feature and more like someone has accidentally emptied several thousand gallons of Gatorade into a mountain basin. It is a shade of turquoise so vivid and startling that your brain almost refuses to accept it as a legitimate colour of nature.

Nature of course is always subject to change, and this scientific process is entirely dependent on the season. In summer, when the glaciers are feeling particularly productive, the lake’s colourful display is more intense. When the mountain runoff slows to a trickle, the water clears into a more traditional blue.

All of this is rather clever really. It’s the sort of grand geological overachievement that makes you feel deeply impressed that nature has found a way to make a physics lesson look so much like a postcard.