Morning Glory Pool

Morning Glory Pool is a hot spring in the Upper Geyser Basin, reached on an easy 1.5-mile walk each way from the Old Faithful Visitor Center. The path crosses boardwalk and paved trail past other geysers and thermal pools, so the walk is part of the stop. If you're already exploring Old Faithful and have time for one more stretch, this is a good one; plan on about three miles round trip.

The pool's green center and rings of yellow and orange are easy to see from the designated walkway. For a photo, frame the whole pool with the colored rim around the center; that keeps the pattern and depth in view. Stay on the boardwalk, and never throw anything into the spring. Hydrothermal water here can severely burn you.

Morning Glory sits in a basin famous for its geysers, but it doesn't erupt. Water flows freely through its underground plumbing: cooler water at the surface sinks, hotter water replaces it, and the system doesn't reach the temperature needed to trigger an eruption. The spring averages 159.3°F (70.7°C).

The pool was named in the 1880s for its resemblance to the blue morning glory flower, and it was once a much deeper blue. For decades, visitors threw coins, rocks, and trash into it. Debris settled in the vent, restricting hot-water circulation and lowering the temperature. Cooler water let orange- and yellow-colored microbes thrive around the pool. Natural changes also contribute, so the human share of the color change isn't certain. Rangers partially drained the spring in the 1970s to remove trash, but the blue didn't return.

Until 1972, the old park road ran through Upper Geyser Basin between Morning Glory Pool and Old Faithful. Traffic was damaging thermal features and putting visitors at risk, so the road moved to the basin's edge. Today, you experience this stretch on foot, with other geysers and springs along the way.