From the Biscuit Basin parking area, cross the Firehole River on the footbridge and continue along the boardwalk. On the right, you'll pass an active spring known as Black Opal Pool, with larger Wall Pool just behind. Thereafter, you'll reach a deep, dark blue spring marked "Sapphire Pool." Until the big earthquake of August 1959, it was a very hot but relatively small geyser, surrounded by a delicate buildup of silicon dioxide scalloping that resembled small biscuits. Following the quake, explosive eruptions occurred, reaching a height of 150 feet. Attendance for its frequent displays rivaled even that of Old Faithful
. But alas, Sapphire's eruptive powers waned with time and by the mid-1960s it had returned to its passive pre-earthquake character. None of the delicate scalloping that gave the basin its name survived the violent eruptions.
Just past the junction with the loop trail, as it joins from the right, Jewel Geyser is reached. It is named for the lovely beads of sinter around its vent. A bit further on the left is Shell Geyser. Its fun to guess the names of features or to look for the namers reasoning. Can you see the resemblance to a yellow clam shell? Next are Silver Globe Spring and Avoca Spring.
At the trail junction stay right and loop around the boardwalk. There is also more subtle activity in geyser basins. Look closely, you may discover a small dark-colored shore fly. A "vegetarian," the fly feeds on the algae and bacteria that thrive here. With luck, you may also spot a wolf spider, tiger beetle, or a bird known as a killdeer. These are the "carnivores" of the basin. They prey on shore flies and their orange-colored eggs for nourishment. Many of these life forms are so perfectly adapted to the basin, they can be found in no other environment.
Thanks to guidebook author, Tom Carter, for sharing this trail description. To learn more about visiting Yellowstone, check out his book, Day Hiking Yellowstone