|Investigations of the Patterns Of Minor and
Major Activity of Steamboat Geyser, 1982-1984
Paul Strasser, Suzanne Strasser and Bill Pulliam
This excerpt from GOSA Transactions, Vol. 2, pp 43-70, 1989, is reproduced here with the author's permission. Transactions are available through GOSA.
ABSTRACT. Prior to 1982, the major eruptions of Steamboat Geyser were believed to be completely unpredictable and random events. Between 1982 and 1984, our intense studies of Steamboat led to the discovery that, contrary to the previously held belief of unpredictability, all observed major eruptions were preceded by specific changes in behavior of its frequent minor activity. The most important aspect of the minor activity was the relative timing of the start of play from each vent (vertical or oblique, sustained or intermittent) was also significant. During the days or weeks preceding a major eruption, the minor play progressed through a fairly consistent pattern of behavior. This pattern was clearest when major eruptions occurred at short intervals. No simple pre-major indicator could be identified without knowledge of the progression of minor play since the last major eruption, thus single observations of minor activity were of little significance.
Since Steamboat is currently the world's tallest geysers - and arguably the most spectacular - it is expected that individuals will wish to devote considerable time to its study when it again enters an active phase. We hope that the information included herein will assist future observers to better understand Steamboat and possibly witness one of its major eruptions, which undoubtedly is Yellowstone's most marvelous attraction.
STEAMBOAT GEYSER: LOCATION AND APPEARANCE. Steamboat is currently the world's tallest geyser. Eruption heights have been directly measured at over 115 meters [White, Hutchinson, and Keith 1988] and estimated by means of photography in excess of 130 meters [Hirschmann 1978]. The only other geyser in the world history to erupt higher was Waimangu Geyser of New Zealand, which erupted in excess of 300 meters in height. Waimangu has not erupted since 1914; thus Steamboat has ranked as the world's premier geyser for nearly a century.
Steamboat is perhaps the loudest geyser in the world as well. Those individuals who are fortunate to see a major eruption from the immediate vicinity can attest to the extraordinary volume of noise, especially during the phase change from water to steam. It is often so loud that one must literally shout to be heard. Many observers have stated that the volume is painful.
Steamboat is located in the Back Basin of Norris Geyser Basin. Its twin vents are at an elevation of 2303 meters, perched halfway up a hill overlooking the drainage of Tantalus Creek (figure 1). Of the geysers at Norris, only Steam Valve Spring and Harding Geyser, both minor and infrequent performers, are at a higher elevation [White, et al. 1988]. Steamboat's vents emerge from a hillside of Lava Creek Tuff overlain by a thin sheet of siliceous sinter deposited by the activity of the geyser itself. This sinter is tinted in various shades of yellow, red and magenta. The terrain surrounding Steamboat is barren and devastated. All soil and vegetation has been removed by the enormous floods of water and debris ejected by the major eruptions.
Steamboat's two vents are presently known as the north vent and the south vent. Earlier reports referred to them as the west vent and east vent [Weed 1883], but this same observer described them as "north vent" and "south vent" only two years later [Weed 1885]. Other observers [White, et al. 1988] referred to them as by the somewhat more accurate northwest-southeast appellation. To make matters even more confusing, a former Norris Naturalist with tongue in cheek once referred to these vents as the "northwest upper" and "southeast lower," in an effort at both complete accuracy and joking pendantism [Hirschmann 1978]. The north-south names were used by all other observers in the 1970's and 1980's; they will be used here.
Upon close visual inspection, the south vent is found to consist of two separate orifices (figure 2). The northern of these is the true south vent; the other does not take part in the frequent minor activity and acts primarily as a drain for some of the south vent's minor play discharge. Bill Pulliam reported that during the June 28, 1984, major eruptions he observed stream, under pressure, emanate from this opening [Pulliam 1985].
Mention must be made of another supposed "third vent" of Steamboat. During the May 20, 1982, major eruption, Paul and Suzanne Strasser observed what appeared to be a third column of water between the rising water columns of the north and south vents and immediately adjacent to the north vent's main water column. This third column of water was a perfect obelisk in shape, similar in appearance to Grotto Fountain Geyser, but considerably larger [Strasser 1983, 1984]. Other observers have seen a similar phenomena. Bill Lewis, a naturalist stationed at Norris in the 1960's stated that he had seen the " third vent" and has a photograph of a major eruption that shows three distinct water columns [Lewis 1982]. However, there is no evidence of a third vent either on or near the surface within either of the main vents. It is possible that a natural obstruction within the north vent can cause its water column to split into two, resulting in both the highest water column and the smaller obelisk of the "third vent". This is the unprecedented in Yellowstone. A rock projection within the crater of Fantail Geyser causes the water from its single vent, an orifice that ejects water violently and horizontally at depth, to be hurled in widely different directions and actually emerge from two pools separated by a spine of sinter [Wolf 1989].
For most of its history, Steamboat's only known subterranean connection was with Cistern Spring, located at the base of the hill about 95 meters from Steamboat's south vent and an altitude of 2292 meters. The connection manifested itself after a major eruption of Steamboat when Cistern's water level slowly dropped over a one-day span, the total drop in water level ranging