Fly Geyser, Nevada

Fly Geyser sits on Fly Ranch in Washoe County, Nevada, about 20 miles north of Gerlach on the edge of the Black Rock Desert. It isn't a fully natural feature in the way a hot spring is — it exists because of two accidents of drilling. The first well, sunk in 1916 while searching for irrigation water, struck near-boiling geothermal water instead and was abandoned, leaving behind a small calcium-carbonate cone. In 1964, a geothermal energy company drilled a second well nearby; the water wasn't hot enough for power generation, so the well was capped, but the seal later failed. Pressure from that second well took over, drying up the original geyser and building the cones and terraces seen today.

The mound itself is a travertine formation, built from calcium carbonate and silica dissolved out of the geothermal water and deposited as it evaporates. Researchers who have studied the site report unusually high silica content, which has let quartz form inside the geyser far faster than the roughly 10,000 years it normally takes — one scientist who has examined geysers elsewhere called Fly Geyser unlike any other she had studied. Water constantly jets from several conic openings on the mound, reaching about 5 feet into the air, and has built 30 to 40 travertine pools spread across roughly 74 acres. The vivid greens and reds across the mound come from thermophilic algae that thrive in the hot, mineral-rich water.

As a jigsaw, the mound is the puzzle's centrepiece and its hardest region — the mottled reds, oranges and greens shift gradually rather than in sharp blocks, so pieces are best sorted by subtle hue before fitting. The flat blue sky and the still pools reflecting it are the fastest sections to place, and make good anchors to build outward from toward the textured mound and the pale desert grasses at the frame's edges.