Bacterial mat at Grand Prismatic photo 10 months 0 Grand Prismatic Spring Overlook timelapse photo 10 months 0 Grand Prismatic Spring from the boardwalk photo 10 months 0 Hat in Grand Prismatic photo 10 months 0 Excelsior Geyser Crater on a spring afternoon photo 10 months 0 Excelsior Geyser Crater photo 10 months 0 Grand Prismatic Spring boardwalk timelapse photo 10 months 0 Turquoise Pool at Midway Geyser Basin photo 10 months 0