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Kinter and Roberts said the indentations are streambeds that their Patwin ancestors committed to memory for when they needed water.

Burrowed into streambeds and rarely moving for their decades-long lifespans, freshwater mussels are biomonitors, meaning they indicate how clean their environment is, according to Penn State researchers.

Rusty red deposits in streambeds are distinctive signs of iron sulfide oxidation.

But just a third of a mile farther upstream, the fish will slam into a pile of boulders and junk metal, before confronting two concrete pipes perched 5 feet above the streambed.

Large quantities of glacial meltwater churn up rocks and sediment, allowing very little light to reach the streambed, while freezing temperatures and snow in other seasons provide little opportunity for a rich microbiome to develop.