Red stone spheres 2.5 metres across that grew on the floor of an inland sea
Giant red spheres lying loose on a bare hillside in the dry country southwest of Medicine Hat, some of them 2.5 metres across, which puts them among the largest concretions on Earth. They are not boulders that rolled here. Each one grew in place on the floor of the Western Interior Seaway about 80 million years ago, as sand, calcite and iron oxide gathered in layers around a nucleus of shell or leaf or bone, the way a pearl builds. The iron oxide is why they are red. The Bearpaw Formation that holds them lies just under a thin skin of soil, so erosion keeps stripping it off and setting more of them out, with badlands and hoodoos around the edges. A Provincial Natural Area, 54 kilometres south-southwest of Medicine Hat and 26 south of Seven Persons on Highway 887. No facilities, no shade, and rattlesnake country.
Near Seven Persons, southeastern Alberta
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