Squeaky sand

This morning, my walk on the beach was accompanied by a soundtrack of squeaking sand. If you've done much walking on the beaches here, you've probably also heard it, and maybe you've wondered what causes the sound. As it was explained to me, it happens when two types of sand granules rub against one another. It's more prevalent when the sand is dry.

So there you go - that's your bit of useless trivia for the day!