This excellent hydrothermal area is often overlooked because its close proximity to the Old Faithful Area. It's a shame, because there are some really interesting and beautiful features here.
The Black Sand Basin is found just west of the Old Faithful Interchange (in the direction of Madison Junction). The parking area is just south of the road. The basin is named for Black Sand Pool, which lies on the opposite side of the highway. Before the Interchange was built, visitors following the spur road from Giant Geyser to Black Sand Basin passed Black Sand Pool. A trail still leads to it, but it is infrequently visited.
The basin lies on either side of Iron Spring Creek. Early geologists mistakenly attributed the red color on the banks of the creek to the mineral iron - it's actually red because of cyanobacteria living in the hot spring water. Just across the creek from our first stop is Cliff Geyser. The geyserite buildup next to the creek is the "cliff" that gives the geyser its name. It has changed character over the years, but most often it erupts 10 to 15 feet high in intervals of less than 3 minutes.
The boardwalk passes Green Spring and crosses the creek. Turn left at the junction and follow the boardwalk out to see Emerald Pool. Its beautiful emerald tint is caused by the blue water in the deep pool combining with the yellow bacteria growing on the sides of the bowl.
Return to the boardwalk junction and take a left. Soon you'll pass (on the right) a big, beautiful Rainbow Pool. Its crater is nearly 100 feet across. Sunset Lake is an even larger hot spring. It was named for its intense flame-like colors. Both springs have in the past temporarily erupted as geysers.
The most famous feature of the basin, Handkerchief Pool, no longer exhibits its unique characteristics. From the late 1800s through the 1920s visitors were encouraged to put their handkerchief in the small pool. The water would suck it down and a few minutes later would return it to the top "nice and clean." Today placing objects in any hot spring or geyser is illegal and very damaging to the delicate features. The remnants of Handkerchief Pool are located in the runoff channel of Rainbow Pool.
Thanks to guidebook author, Tom Carter, for sharing this trail description. To learn more about visiting Yellowstone, check out his book, Day Hiking Yellowstone