CISTERN SPRING—In 1966 this feature changed from a grayish-black color to its present brilliant blue. Concurrent with this the overflow increased killing many trees near the spring. Since then a silica terrace has rapidly built up. When Steamboat had a major eruption the water level in Cistern dropped 4-8 feet, (1.2-2.4 m.) with a corresponding drop in water temperature of around 60 degrees F. This seems to indicate some connection between the two features. Whether or not the increased water output of Cistern has resulted in the decline of Steamboat is still unknown. ECHINUS GEYSER (ē-kī′-nŭs)—although not as well known as some other geysers, erupts in a display that surpasses many of them. The name comes from the sinter spine-covered rocks surrounding the pool which bear a fanciful resemblance to spiny sea urchins. _Echinus_ was the Greek name for these tide-pool dwellers. Stop and watch the water fill the basin and begin to boil. Soon it will be propelled skyward in great explosive bursts of steam and water, some reaching heights of over 75 feet (23 m.). Usually the eruptions last three to six minutes but in 1977 Echinus was erupting for up to twelve minutes. After erupting the pool drains and begins to refill. Intervals between eruptions may be as short as 45 minutes or better than 75 minutes. Listen for the peculiar gurgling sound produced as the vent drains after each eruption. VIXEN GEYSER—Although its usual eruptions are small compared to others (5-15 feet every few minutes), the geyser is unique in that water comes from a circular tub-like vent. During normal activity little water is ejected. Occasionally Vixen may have major eruptions of considerable water, lasting 5 to 50 minutes and playing up to 30 feet. Listen for the peculiar gurgling sound produced as the vent drains after each eruption. TODAY’S GEYSER PREDICTIONS (Obtain data from the museum prediction board or from a naturalist). Echinus ______________________________ Ledge ______________________________ Valentine ______________________________ Others ______________________________ ______________________________ ______________________________ Text written by George A. Algard, Norris Summer Naturalist 3/74 4/78 [Illustration: NORRIS GEYSER BASIN]