12,000 years ago, Yellowstone’s dry summers began leaving a charcoal trail in its lakes. 6,000 years later, researchers found the same climate pattern linked to lower lake levels and reduced hydrothermal activity

Long before modern climate records existed, Yellowstone’s lakes were preserving evidence of changes in climate, wildfire activity, and hydrothermal systems.

A new study led by Montana State University researchers examined sediment from small lakes in Yellowstone’s Lower Geyser Basin. The records show that summers were warmer and drier than today between 12,000 and 6,000 years ago, as per a report. During that period, more charcoal accumulated in the lake sediments, while diatom records indicated lower lake levels.