Between a Rock and a Hard Place

Bruce Macdougall snapped this unusual photo on the beach outside his parents’ home on South Beach where they’ve lived since 1978. “Until this past winter, we never saw the bedrock this exposed,” said Bruce, but during an extremely low tide, he and his sister, Alison Lampe (a trained archaeologist), spotted the embedded concretion—a compact mass of mineral matter found in sedimentary rock. Geological curiosities, concretions take various shapes and are often mistakenly identified as dinosaur eggs, animal and plant fossils, extraterrestrial debris or human artifacts. After a little sleuthing, Bruce and Alison confirmed that this particular finding formed around a plant or animal that had crystalized, which explains its shape. “Concretions are common as loose objects on Puget Sound beaches,” said Bruce. “We have picked up loose concretions for decades and usually toss them back, but it’s rare to find one embedded in bedrock.”