Artemisia Geyser

Artemisia Geyser is one of the largest pools in the Upper Geyser Basin, a deep blue water bowl edged with pale, almost terraced geyserite. The pool is worth a look even when it stays quiet; when it erupts, the whole surface rises in a rolling boil rather than a narrow jet.

Artemisia sits on the trail that links Biscuit Basin with Morning Glory Pool. It takes a walk beyond the paved basin boardwalks, so treat it as a detour rather than a quick step off the main loop. Check the current park trail map before choosing an approach, and stay on designated trails and boardwalks: hydrothermal water can cause severe burns.

The name refers to the gray-green color of the geyserite around the pool, which resembles sagebrush. Pale deposits build nearly terraced pools around the main blue basin. For a photo, keep some of that branching, pale rim around the water; it gives the blue pool its shape even without an eruption.

Rain and snow seep thousands of feet below the surface, where Yellowstone’s volcanic heat warms the water. Underground cracks carry it back upward, and narrow passages trap steam until pressure pushes water to the surface. That plumbing makes Artemisia’s eruption a roiling boil, and its timing is too variable to plan around.