Section of sediment core from Rush Lake, Lower Geyser Basin, Yellowstone National Park, showing different layers that accumulated over time

Section of a sediment core from Rush Lake, Lower Geyser Basin, Yellowstone National Park. Thick gravel to the left (black-gray) is the product of a hydrothermal explosion that occurred in Lower Geyser Basin more than 13,500 years ago, and fine laminations to the right (very fine layering) may be the product of seasonal glacier melt, pulses of hydrothermal activity, or something else. Photo taken by Christopher Schiller, September, 2023.