9 stunning natural mysteries scientists can't fully explain

The bright-pink Lake Hillier in Western Australia.

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• Some of the most beautiful sights in nature are also mysterious.
• These include sand dunes that seem to sing and a dazzlingly pink lake in Australia.
• While researchers have theories for many of them, questions remain.

Whether it's the cause of a flamingo-pink lake or the source of splotchy circles in the desert, nature holds countless secrets that scientists are still trying to figure out.