THE WHIRLIGIGS AND CONSTANT GEYSERS—these three features seem to be interconnected. Constant Geyser, dormant for several years, reactivated in the early ’70’s and now erupts up to 30 feet (9 m.) once or twice an hour; often prior to an eruption of one of the Whirligigs. In recent years, Big and Little Whirligig have traded active periods. When one is more active, the other is less. Watch for the 15 foot (4 m.) angled plume from Little Whirligig’s orange vent or listen to the distinctive chugging produced during Big Whirligig’s splashing eruption. As with many geysers, the water level rises in these pools prior to an eruption. EBONY AND BEAR DEN GEYSERS—are another set of related features. In the ’60’s Bear Den Geyser first appeared and as it increased in activity, Ebony Geyser became dormant. Today Bear Den Geyser erupts in bursts, arcing up to 40 feet (12 m.) from the den-like vent, four to six times daily. The death of Ebony Geyser may have been hastened by objects thrown into its vent by thoughtless visitors. This debris is cemented into place by the silica deposited from the water, choking off the vent. Minute Geyser in the Back Basin may have suffered a similar fate. THERMAL FEATURES IN BACK BASIN EMERALD SPRING—The colors in and around thermal features are often created by several kinds of algae that grow in hot water. However, the deep green color of this spring is a result of a combination of the yellow color from the sulphur lining the edge of the pool with the blue that is refracted (“scattered”) from the clear water in the pool. The bowl of this feature is about 27 feet (8 m.) deep and the temperature normally varies between 194 and 200 degrees F. (90-93° C.) STEAMBOAT GEYSER—The world’s largest geyser, Steamboat has eruptions of more than 300 feet (91 meters). It was largely dormant for nine years, then startled observers in March 1978 with a full-scale eruption. The water phase lasted approximately 20 minutes, followed by bellowing steam for over 40 hours. This spectacular display inundated the immediate area. At this writing, March 30, 1978, it is not known if Steamboat’s eruptions will follow any pattern. Between 1961 and March 1969, it had a total of 103 major eruptions, none of which could be predicted. You can still see the effects of downpouring water on the landscape which killed trees and scoured away soil. The nine-year respite allowed new lodgepole pines to gain a foothold. We hope you are fortunate enough to witness Steamboat Geyser and share in the excitement. Remember—protect camera and eye glass lenses from the spray as it can scratch glass after drying.