Rock Circles: Geologically Curious Phenomena (GeoShort)

07.15.2021 - By PlanetGeo: The Geology Podcast

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Our GeoShort today focuses on Spherical Weathering, where normal rocks are turned into round shapes by chemical erosion.

Many rocks have cracks in them, called joints, and these joints often break the rocks up into little cubes or rectangular prisms.  Cubes and prisms have a high surface area relative to their volume, and the corners especially.

So fluids that have weak acid in them preferentially eat away at the corners, eventually turning the cube of rock into a perfect sphere!  Spheres have the lowest Surface Area/Volume of any shape, because they have no corners or edges left.  The rock just gets made into a smaller and smaller sphere then.

While spherical weathering is not a common process, it is not rare either.  So, keep an eye out when you are outside next, you may find some Spherical Weathering near you!

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