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Black Sand Basin - Yellowstone National Park

The boardwalk passes Cliff Geyser, Sunset Lake, Emerald Pool, and Green Spring. Part of Upper Geyser Basin.
Rating: 5 out of 5 by EveryTrail members
Difficulty: Easy
Length: 0.4 miles
Duration: Less than 1 hour

Overview :  The following is taken from http://www.yellowstonenationalpark.com/blacksand.htm:

Black Sand Basin, an isolated group of the Upper... more »

Tips:  Hydrothermal features are fragile rarities of nature. Yellowstone preserves the largest collection of hydrothermal features on the... more »

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Points of Interest

1. Opalescent Pool

Temperature 144°F Dimensions 28x55 feet. Depth 6 feet. Opalescent pool has a cooler temperature than other thermal features at Black Sand Basin. Early in its history Opalescent was a boiling spring, surrounded by smaller springs. In the early 1950s it was a small dry pool, then the run-off from Spouter Geyser flowed into it. The increased water... More

2. Spouter Geyser

Temperature 199.9°F Interval 1-2 hours. Duration 10-11 hours. Height 5-7 feet. Spouter Geyser, once believed to be a continuous geyser, does erupt almost constantly with only a short 1 to 2 hour interval. It is a fountain-type geyser and erupts from a splashing, undulating, blue pool of water. The jets shoot through the pool to a height of five to... More

3. Cliff Geyser

Temperature 191.8°F Interval irregular. Duration 30 minutes to 3 hours. Height 40 feet. A. C. Peale, geologist for the 1872 Hayden Expedition, named this feature for its cliff-like wall of geyserite formed around the crater and for its location on the edge of Iron Creek. An indication of a pending eruption is that the crater nearly fills with... More

4. Green Spring

5. Emerald Pool

Temperature 154.6°F Dimensions 27x38 feet. Depth 25 feet. Named for its emerald green color, it is one of the main attractions at Black Sand Basin. The color is the result of lower temperatures which have allowed yellow bacteria and algae to grow on the lining of the pool. The clear water of the pool reflects the blues but absorbs the other hues... More

6. Rainbow Pool

Temperature 161°F Dimensions 100x130 feet. Depth 27 feet. The edges of this pool display the color of the rainbow, hence the name. Algae and cyanobacteria are responsible for the varied colors. This pool has only erupted a few times in the past. During one eruption in 1948 it reached a height of 25 feet. The last known eruption was in 1973. The... More

7. Sunset Lake

Temperature 180°F Dimensions 145x191 feet. Depth 23.5 feet. Sunset Lake is a shallow thermal pool with a soft sinter bottom and yellow and orange bacteria and algae edges. The pool discharges into Iron Creek, and overflows into Rainbow Pool creating a large microbial mat between the two thermal features. The 1959 earthquake triggered an eruption... More