The blue colour of General Carrera Lake is due to small particles carried by the ice in the glaciers, which remain suspended in the water once the ice melts. The glacial meltwater is slightly turbid and refracts the blue part of sunlight.
The caves are made entirely of marble: marble forms when limestone or dolomite is metamorphosed. The whole block of marble has been calculated as weighing 5 billion tons; the stone is light grey in colour with some darker striations. The marble was exposed by the movements of glaciers during the Pleistocene. The caves were formed from wave action over 6,200 years, as water penetrated the huge blocks of rock and carved them in such a way that they formed beautiful caves and tunnels.
Marble, being made of calcium carbonate, is slightly soluble in water. When the lake reached its present level, the process of solution started. The marble began to dissolve, and it dissolved faster at the water surface. Small cracks within the marble were gradually worn into wider fractures; waves washed away the dissolved material. It took only a few thousand years to create these caves and tunnels.
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