In cold weather, a new geological feature has shown up at Utah’s Great Salt Lake in the last decade. These salty mirabilite mounds form terraced crystals that resemble Yellowstone’s Mammoth Hot Springs.
Mirabilite is hydrated sodium sulfate (as opposed to the sodium chloride of table salt). The structures form when upwelling spring water partially dissolves the layer of mirabilite found beneath the lake bed. That sulfate-laden water rises to the surface, where it freezes into the crystals seen here.
When temperatures rise above freezing, the water in the mirabilite evaporates, leaving behind white, powdery thenardite. (Video credit: Great Salt Lake Institute; image credit: Utah Geological Survey)
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