By
Paul Strasser, Suzanne Strasser and Bill Pulliam
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Investigations of the Patterns Of Minor and
Major Activity of Steamboat Geyser, 1982-1984 By Paul Strasser, Suzanne Strasser and Bill Pulliam |
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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 between a half meter and an empty crater. Cistern typically refilled after another three to four days.
On rare occasions Cistern erupted in a series of voluminous splashes to a height of two meters (figure 3). These eruptions have only been observed at the start of the draining process following the start of a Steamboat eruption.
There has been some speculation as to the possibility of Cistern predicting major eruptions of Steamboat. Rocco Paperiello [1988] attempted to correlate the amount of discharge from Cistern immediately preceding eruptions of Steamboat. The results were mixed at best, and further study is warranted before any statement expressing certainty, either in the positive or in the negative, , is given. Since Cistern's discharge spreads over a large area rather than a well-defined runoff channels, any attempts to accurately measure changes in runoff are difficult. A possible course of action might be to measure changes in either Cistern's Ph or temperature for long periods of time and correlate these measurements with the behavior of Steamboat.
Since 1982, studies have suggested connections between Steamboat and other features on a much larger scale than previously believed. One spring in the direction of Cistern that might be connected with Steamboat is a large hot spring about 30 meters south of the boardwalk, the line with the large gully created by the north vent's discharge. In 1982, this spring was a large crater filled with boiling water. In 1986, it had changed to a quiet spring filled with clear water of a deep green color. This spring has no name, although it was referred to as the "black thing" in a few correspondences [Pulliam 1984, Strasser 1984].
The only reason that there is and conjecture regarding a possible connection with Steamboat is that this spring has evidently undergone the same metamorphosis as Cistern, which until the early 1960's was a crater filled with dark gray, boiling water and has since changed into one of Yellowstone's most attractive hot springs [White, et al. 1988]. Of course, a similar metamorphosis does not guarantee a connection, but is location and changes in appearance perhaps warrant it for further study.
The other connection id the Echinus-Steamboat-Emerald Spring line of thermal features. They were all affected on numerous occasions by minor disturbances affecting only this area of the Back Basin. During these events, called "mini-zaps" by Paperiello [1984, 1988], Emerald Spring boiled more heavily and occasionally became less transparent, Steamboat's minor activity slowed considerably, and Echinus Geyser changed from a frequent, regular performer into a geyser with eruptions that would last from 5 minutes to over 100 minutes, with intervals changing in a similar manner.
This connection was first mentioned by Fred Hirschmann [1979]. He told the Strassers on several occasions that when emerald Spring was boiling more heavily Steamboat's minor play quieted. The year 1979 was also the first in which irregular Echinus with unusually long eruptions was observed. The connection between Echinus and Steamboat was not surmised during 1979; the investigation into this connection was not undertaken until Paperiello's efforts in 1984 [Paperiello 1988].
One other connection must be noted. Every feature at Norris Geyser Basin is frequently affected simultaneously by a phenomena called a widespread contemporaneous change [White. et al. 1988], but more commonly known by the more general term "disturbance." Disturbances usually take place about once a year, and were originally called the "Autumn Disturbance" because several had taken place in September r October. In more recent years the disturbances have occurred as early as May; the seasonal adjective has thus been dropped. The most detailed studies of the disturbances have been by White, et al., and Paperiello [1988]. Steamboat Geyser is immediately and profoundly affected buy a disturbance, when its minor activity abruptly diminishes in power and frequency. Generally it takes several weeks for Steamboat to recover from the effects of disturbances. It should be noted that Steamboat is the only feature whose activity level typically declines after a disturbance.
MAJOR ERUPTIONS IF STEAMBOAT GEYSER. An eruption of Steamboat is an extraordinary event . Everything about it is a superlative. Steamboat's vaunted rank among Yellowstone's geysers is fully merited. Many of the great geysers along the Firehole River - Grand, Beehive, Splendid, and Giant, among others - are estimated to have a maximum height of "200 feet," although measured eruptions rarely attain that magic, round-number height. Steamboat's eruptions routinely attain a height of 100 meters (300 feet) and have been estimated in excess of 130 meters (400 feet) [Hirschmann 1978]. Steamboat's water spreads out slightly in a minor fan-shape; when viewed from one of the observation platforms, located approximately 30 meters from the vents, the water is literally straight up (figure 4).
Despite all the attention that Steamboat received in the 1960's, with reports of observers camped out for months on end to see Steamboat erupt, there is surprisingly little written information about the nature of the start of its major eruptions. Modern observers have heard reference to a "silver bullet"; one source said it was "... a steel jacketed bullet, a gleaming shaft of water shot skyward from the north vent... like a rifle shot" [Crellin 1964].
This description is diametrically opposed to the start of the Steamboat eruptions on the 1980's. Instead of a sudden blast of water to 100 meters, Steamboat was almost leisurely in its ascent. The water shot swiftly to 20 meters and then slowly grew, with small fingers of water reaching above the general mass of water. This continued until the play was at maximum force. It took fully twenty second to attain maximum height.
By the time the water reached a height of approximately 35 meters, its changed from a lustrous white to a milky hue tinged with brown. Some observers suspect that the color change was caused by the tapping of a distinct subaquifer underneath Steamboat. They believe that only a major eruption taps the deeper water and the change in its appearance is the best indicator that an eruption has truly started. It is also possible that come of this color change is caused by the eruption itself; much of Steamboat's discharge land upslope from the vents and flows down into the water jets. Some of the surface dirt and rocks carried by this downhill flow of water would be hurled into the air, thus enhancing the dirty appearance.
The play from each vent had its own character. The water from both merged for the first 30-40 meters; although the two water columns were were discernible they formed a nearly unbroken curtain of water. At this height, the south vent's water divided and erupted at a slight angle to the southeast and attained a height of 50-70 meters. The north vent's fountain reached the maximum height, erupting a steady stream to over 100 meters at a slight angle to the northwest. Maximum height was reached early in the eruption; it continued at or near maximum height for most of the water phase.
Since the water angled uphill, away from the vents, many eruption height estimates may have been slightly too short. Observers frequently made height measurements from the far side of the Tantalus Creek drainage at the spot known as "Decker Island," from where the tallest water is farther from the viewer than a perpendicular calculation of the vast distance would assume. Any height measurements taken from near Steamboat is of little value since the angle of the top of the water might literally be 90 degrees the the observer.
The volume of water discharged during a major eruption is enormous (figure 5A). No precise calculation of the discharge has been attempted but was estimated by White, et al. [1988], at about 20,000 liters per minute. The water in Steamboat's two main runoff channels was a roaring cascade that flooded the entire Tantalus Creek lowland with steaming muddy water.
The amount of debris within the water was impressive. Mud from eroded soil turned the water a Cafe Au Lait color. Rocks were hurled into the air with impressive force; these ranged in size from gravel to fist-sized (figure 5B).
The length of the water phase varied from 7 to over 16 minutes. The precise length of this water phase was not easy to determine since the change to steam was gradual, taking tow or more minutes. Most recorded water phase durations from the 1980's were based on the midpoint of the transition from the time of primarily water eruption to primarily steam eruption.
After the astonishing height of the water phase, the power of the steam phase was frequently a mind-numbing sensory overload. The most common reaction of the most experienced observer was, "I don't believe it!" The steam left the vents with such force that its motion in the first 10 meters of height was a blur to the eye.
Other geysers have well-regarded steam phases. Castle's can be heard over a half kilometer away, Splendid's rare steam phase eruptions in 1973-1974 could be heard over 1 km away [Wolf 1978], and a superlative Giantess steam phase might be heard 2 km away. These are surely impressive, but they pale in comparison to Steamboat, whose steam phases were frequently a painful assault on the auditory system. The routinely awakened campers at the Norris campground, located 6 km distant. There are reports from the 1960's that an eruption of Steamboat was once heard at Madison Junction and air distance of over 14 km [Bryan 1986], and a report from 1891 of an eruption heard (and felt) at Mammoth Hot Springs, over 29 km away [Hague 1915].
The noise of a steam phase was normally comprised of two distinct frequencies. One was almost subsonic, felt as much as heard. It pounded against one's chest in palpable waves. The other frequency was higher, a pitched roar so loud that the air seemed incapable of carrying such a load of sonic energy. The sound was distorted into a tortured, rapid-fire series of crackles and pops. "It was reminiscent of a Saturn V rocket at liftoff, but instead of any man-made rocket blast, Steamboat was a pressure release valve of Spaceship Earth. "'Shouting to be heard' was literally impossible" [Strasser 1984].
The decibel level the steam phase varied considerably. Some observers [Hutchinson 1984, Pulliam 1989] believed that external factors, including wind, temperature and humidity, had a large effect on the noise volume, the loudest steam phases noted during periods of cooler, humid weather. For example, on August 23, 1978, Steamboat erupted at 08:30. The Strassers arrived a little before 11:00; when they stopped their car at Norris Junction they lowered the car window and heard a dull roar in the distance. Steamboat was approximately 1 km distant, the eruption had started nearly three hours earlier, and the roar could still be heard over the sounds of traffic.
The steam phase of June 20, 1982, eruption was exceedingly loud. Paul Strasser wrote, "All those tiny little bones in my ears were protesting that they'd really prefer to be elsewhere" [Strasser 1983]. In contrast, the steam phase on August 4, 1982, although very loud in its initial stages, was barely discernible at the parking lot walkway entrance to the Basin, a distance of a few hundred meters, only three hours after the eruption.
Typically, after 30 minutes the force of the steam phase began to wane. It then became merely very loud, being heard only two to three kilometers distant. The precise length of the steam phase was not given; over the course of 6 to 12 hours it slowly waned in force, finally ending in a gentle welling of steam.
INVESTIGATIONS INTO THE MINOR ERUPTIONS OF STEAMBOAT. On January 3, 1982, Steamboat Geyser erupted for the first time since June 16, 1979. The January eruptions was greeted only with mild interest, primarily because Steamboat's eruptions had been rare events since early 1969. The only eruptions in the intervening 13 years were two in 1978 and one in 1979. There was no reason to believe that the January eruption was anything other than one of its rare and unpredictable displays.
On February 11, 1982, Steamboat erupted again. This 39 day interval was the shortest on recored since June 1967. Interest in Steamboat Geyser grew dramatically. When another eruptions occurred on February 21 and three more took place in March, it was evident that Steamboat had entered a new period of frequent eruptions.
The road opened to the public in mid-April. During the next three months Paul and Suzanne Strasser spent considerable time at Steamboat. Since they were with the accepted "common knowledge" about the unpredictability of Steamboat's major eruptions, they spent the first day merely waiting and reading newspapers while sitting in beach chairs firmly embedded in the remnants of the winter snowpack. Except for brief glances at some of the minor eruptions, they ignored Steamboat, since they were familiar with the generally accepted belief that Steamboat was inscrutable and unknowable. Such activity quickly became boring, so during the next observing session they began data collection of Steamboat's frequent minor plays.
Considering that Steamboat had and average of 30 to 40 minor eruptions per hour, the note-taking was copious, especially since there was no idea of what purpose it would serve. Several basic approaches were tested, including intervals, durations, height, and the massiveness of the minor eruption. The principal result of this initial note-taking activity was that interest in the geyser was maintained.
During the first few viewing sessions nearly all of the minor eruptions initiated by water from the north vent, which was typically a thin jet of water sprayed obliquely at an angle offset 30 degrees from vertical towards the northwest with a duration of one to ten seconds. A few seconds following the start of the north vent, the south vent would occasionally join in, throwing an oblique jet of water to the east. The south vent's play was generally lower than the north's, although the volume of discharge appeared to be at least the equal of the north's.
All of the early observing sessions were between major eruptions, which were then occurring at intervals of 4 to 12 days. There was no evidence of differing minor behavior than that described in the previous paragraph. Upon their arrival on May 14 at Norris - five days after Steamboat's most recent eruption - other observers informed them that Steamboat had resumed having minor eruptions.
After a few minutes of observation it was apparent that the minor plays were markedly different from those previously seen. Instead of the north vent initiating the minors, the south vent was first to play. The other gazers noted that Steamboat had been erupting like this for several hours and were unaware that this new behavior was different. These minor eruptions were also of greater volume than those observed during earlier sessions. The south vent's play was so great that some of its discharge trickled down its wide, deep gully. By the time the runoff reached the boardwalk at the base of the hill, it was no more than a slick of water on the rocks, but it was certainly different. Its eruptions were consistently more powerful than those previously observed. Instead of the thin oblique jets seen earlier, the new play was much more massive and longer lasting, with heights attaining 10 meters and durations of 5 to 15 seconds.
The next morning the observers noted another type of south vent minor eruption. Intermixed with frequent oblique jetting was a vertical column of water that was much more voluminous than the oblique jets. Over 90 percent of all minor plays were initiated by the south vent. The remainder were comprised primarily of brief, thin jets of water from one vent or the other.
Steamboat Geyser was kept under close scrutiny for the remainder of the May 15-16 weekend. Its eruptions continued to be initiated by the south vent. On the evening of May 16, with no warning whatsoever, there was a minor play initiated by the north vent. The next minor was similar, as well as the next few. The south vent's play had quieted considerably and Steamboat looked like it during earlier observation sessions. For the remainder of that evening the north vent initiated the minor plays. Observers left disappointed, believing that a major eruption was due soon since it had already been seven days since the most recent major.
By Thursday, May 20, Steamboat had not yet erupted and the Strassers arrived at Norris in the early morning. Within minutes it was apparent that Steamboat had again changed its mode of behavior. Instead of minor plays initiated by either the north vent or the south vent, nearly every minor eruption began in both vents simultaneously, or within less than a second of each other. The volume of discharge and height had grown considerably. Many of the north vent's plays reached 12-15 meters, while the south vent's eruptions approached 6-8 meters. The only minor plays that did not begin simultaneously were occasional very small splashes of water from one vent or the other that were nearly invisible in the cool, moist air. These had the appearance of "sloshing" of water very near to the surface as opposed to a separate, distinct minor eruption.
The vertical jetting previously observed emanating from the south vent was still present and much more forceful. The north vent also occasionally jetted water vertically in a more impressive show than the south vent's play. Since no other observers were present, there was no way to know when the new mode of behavior began
The simultaneous minor plays remained strong and vigorous throughout the morning hours. At 11:45 the strongest minor play yet seen took place3. It was no less than 20 meters high and produced a flood of water down the south vent's runoff channel. The observers wondered: if such a massive minor did not initiate and eruption, what did?
Apparently very little extra was required. Steamboat was quiet for about eight minutes. At 11:54 another play began. It resembled the earlier massive minor but did not stop. Instead it sank a little in height, then simply started climbing. Within 20 seconds it was over 40 meters; in another 20 seconds it was over 70 meters, the water turned a milky brown color, and continued climbing. An eruption was on.
The sheer joy and satisfaction of seeing a major eruption of Steamboat - a goal of geyser gazing that was assumed to be unattainable - did not halt the consideration of was seen prior to the eruption. The variations in minor behavior were striking; the change from south-initiated minors to north-initiated was so abrupt and obvious it was sufficient to give one pause. On May 14, the Strassers first dubbed the north-initiated eruptions as "north function" and the south-initiated eruptions as "south function." These names were originally created simply as an easy way of noting the general behavior of the minor play and explaining the changes to others.
The minor play that preceded the May 20th eruption, in which both vents started almost simultaneously, was dubbed "simultaneous function." Again, the purpose of this name was to simplify a general pattern of behavior in such a way that Steamboat's observed minor activity could be easily explained to someone unfamiliar with the territory.
Since the only pattern that emerged from weeks of data collection was the progression of functions, it was the focus of the investigations during the next few months.
On May 30, Steamboat was again in the mode now called simultaneous function. According to the descriptions of its behavior during the preceding week, Steamboat had again progressed from north function to south function to simultaneous function. During the next three days Steamboat remained in simultaneous function, except for a brief period on May 31, when it regressed to south function.
In many ways, it is regrettable that it did not erupt that day. Being a holiday, there was a large crowd of Park Service employees, Naturalists, and geyser enthusiasts assembled. The temperature was balmy and dry, the sky clear. Regrettably, Steamboat chose to hold off its eruption until less desirable conditions were available.
The next day dawned cold and damp. The large happy crowd of a day earlier was gone. The Strassers were the only observers at Steamboat that morning. Steamboat was still in simultaneous function, but after nearly three days of seeing the same sort of behavior, as interesting in its own right as it might be, they were in no mood for a protract3ed sit - especially when it began to snow. With wet, sticky flakes blowing and a noticeable lack of available cold-weather clothing, they abandoned their post for no better reason than to impede the apparent onset of hypothermia.
Steamboat erupted during the snowstorm. The observers returned, drier and warmer but chagrined, an hour after the start of the eruption. Although disappointed they missed the water phase of the eruption, they noted that the eruption occurred during the same mode of minor activity as had the previous eruption.
Throughout June the pattern continued. The minor eruptions progressed in the manner noted earlier. The eruptions of June 8th and 22nd took place during simultaneous function. By the end of June, it appeared that the progression of Steamboat's minor play was an apparently excellent barometer of its eruption potential. Not only did Steamboat progress through the north, south, and simultaneous functions, but other behavioral patterns were noted. Steamboat was observed to briefly regress either from simultaneous function to south function or from south function to north function, but never from simultaneous to north. In addition, once Steamboat entered simultaneous function it could erupt at any time; the observed range was from 8 hours to over 4 days. Most importantly, it did not erupt while in south or north function.
As June ended, another eruption was anticipated. On June 30, Steamboat was in strong south function when the Back Basin was struck by a small disturbance that affected features along a line from Echinus to Steamboat and on to Emerald Spring. The effect on Steamboat was a regression to a weak north function.
By July 5, Steamboat had fully recovered and was in simultaneous function. On July 6 at approximately 13:00, a stronger and more widespread disturbance struck Norris, affecting features as far removed as Echinus, Hydrophane Springs, and Graceful Geyser [Strasser 1984].
The disturbance's effect on Steamboat was dramatic, but typical. Its minor play declined to enervated small splashes from the north vent. For the next week the only minor plays were small splashes from the north vent intermixed with feeble steam puffs from both vents.
Steamboat took longer to recover from the disturbance than it had from any eruption of 1982. By July 24, Steamboat had entered a weak south function, but after a few minutes of observation a slight difference was noted in its behavioral pattern. Prior to the disturbance, fully 90 to 95 percent of all minor plays were initiated by the south vent when it was in the south function. On July 24, only about 75 percent were south vent initiated plays. This was a subtle but distinct difference.
On August 1, Steamboat entered simultaneous function; like the south function the previous week this first simultaneous function was less distinct than the pre-disturbance simultaneous function. Only about 75 to 85 percent of minor eruptions started simultaneously in both vents.
On August 3 at 11:33, Steamboat displayed a spectacular phenomenon not seen before (figure 6). Both vents started as a typical simultaneous minor eruption but grew in power and force. After playing for ten seconds both vents abruptly stopped; less than two seconds later they burst to life again. Both vents immediately rocketed to an estimated height of over 25 meters. They then grew slowly in height to nearly 30 meters, but suddenly quit entirely. It was unlike any minor seen to that point; it looked very similar to the start of the May 20th eruption, so much so that there was at first shouts of delight from the assembled throng, then groans of disappointment. Following this unusual minor event, Steamboat remained in the less distinct simultaneous function.
At first the authors called this unusual display and "Oh my god" burst. Later that evening while describing the unusually powerful event to other observers, Paul Strasser called it a "superburst" for want of a better name. The authors regret that this unoriginal term has become the accepted name for the phenomena, since the same term has been in common usage for years to describe unusually powerful eruptions of Great Fountain Geyser [Bryan 1986].
On th3e morning of August 4, Steamboat was still in simultaneous function. However, there was little opportunity to observe the nature of the minor play of that date because Steamboat erupted at 09:03, less than 20 minutes after the Strassers' arrival.
The beginning of this eruption was similar to the May 20th eruption. Again, the water rose slowly and majestically rather than like the "silver bullet" description from the 1960's. The maximum height was so much greater than that attained by the more familiar geysers along the Firehole that any estimate would be simply a guess, although it was felt that the August 4th eruption was the higher of the two. In contrast, the steam phase of the May 20th eruption was distinctly louder than the August 4th steam phase, which was barely painful.
The Strassers completed their study of Steamboat for 1982 at this time. They informed every interested gazer of their hypothesis and discoveries. Several gazers, notably Bill Pulliam, continued and expanded on the original work.
SUMMARY AND COMMENTS ON THE INITIAL FINDINGS OF THE RELATIONSHIP BETWEEN MINOR ACTIVITY AND MAJOR ERUPTIONS. As discussed earlier, the initial investigations directly led to a function hypothesis. We noted that the validity of these discoveries may only be of special interest during periods of frequent Steamboat eruptions. A great deal of confusion has stemmed from this fact.
Many observers, upon hearing the basics of the function hypothesis, will observe Steamboat for a while and note that nearly all minor eruptions start simultaneously and thus determine that it is in simultaneous function. Technically this may not be correct, because "simultaneous function" implies that it was preceded by a progressed through a north and south function. A single observation cannot determine prior behavior, thus any prediction of an impending major eruption if fraught with peril. In some years, such as 1985 and 1986, Steamboat was observed to be, for short or protracted periods of time, erupting in a fashion similar to south or simultaneous function. However, there was no clear prior progression of functions, nor were major eruptions occurring with any frequency. Thus, any prediction of the likelihood
of an imminent major eruption was little more than conjecture.
In summary, the following trend of minor activity was noted after the major eruptions during April-June 1982.
2) North Function. The first observed minor play consisted of thin oblique jets of water from the north vent. Over time the play grew more powerful, both in duration and volume. As the strength grew the south vent began to erupt as well. However, nearly every minor eruption was initiated by the north vent.
3) South Function. Without warning the south vent began to initiate the minor plays. During south function both vents were more forceful than their north function minors. It was also during south function that vertical jetting was first seen in either vent's minor play.
4) Simultaneous Function. The change from south function to simultaneous function was also abrupt. During simultaneous function both vents began their plays at nearly the exact same time - within one second. The activity was also more powerful during simultaneous function, with vertical jetting from both vents occurring regularly. Also, the north vent occasionally sprayed a massive, fan-shaped jet of water during simultaneous function.
The following guidelines were not observed to fail during the period of frequent eruptions in 1982.
2) Steamboat Geyser could regress from Simultaneous function to south function, or south function to north function. It was not observed to regress from simultaneous to north, except as an effect of a disturbance.
3) Once Steamboat entered simultaneous function it could erupt at any time. Observed simultaneous function durations (measured from the beginning of simultaneous function to major eruption, including and regressions to south function that might have occurred unobserved) were from 8 hours to over 4 days.
As noted earlier, the behavior of Steamboat following the July 6th disturbance differed from what was observed in earlier months. Steamboat took a much longer time - nearly two weeks - to begin the minor eruptions. Also, the distinctiveness of the separate functions was diluted. It was enough of a change for the authors to wonder if the functions still had validity in determining the likelihood of an impending eruption. In addition, the unusual phenomena dubbed a "superburst," first seen on August 3, was not observed before the disturbance.
BEHAVIOR OF STEAMBOAT AFTER AUGUST 4, 1982: EXPANSION OF FUNCTION HYPOTHESIS. Bill Pulliam arrived at Steamboat during the waning portion of the water phase of the August 4th eruption and was duly impressed at the first sight of Steamboat at full power. The sight was sufficient impetus for him to devote a considerable amount of time to the study of this geyser.
Following the August 4th eruption and the departure of the Strassers, interest in Steamboat was maintained by a large contingent of observers. Some dedicated observers waited on site for ten days. Their reward was a spectacular eruption under ideal conditions at 11:36 on September 6. The height was estimated visually at 90 meters, and photographs confirm at least 85 meters. The interval of 33 days 3 hours was similar in many respects to the prior, disturbance induced interval of 43 days. A notable similarity was the less distinctive appearance of the functions in the days preceding this eruption.
It was during the geyser "sit" that Pulliam began his observations..... [The article proceeds to describe Pulliam's observations and how they differed somewhat from the Strassers. It also presents a mathematical analysis of the observations.]
PROSPECTS FOR FORECASTING MAJOR ERUPTIONS. The term "prediction" when used in conjunction with geyser activity generally refers to a specified period of time, typically no more than hours in length, during which there is a high probability that a specified geyser will erupt. As of now, nothing has yet been discovered about Steamboat to allow predictions of this accuracy and precision. However, the function progression concept and the methods fort recording and quantifying the minor play presented here may yield less specific forecasts of the possibility of a major eruption. These forecasts hinge absolutely of the assumption that the geyser's behavior while under observation will be fundamentally similar to that observed in the early 1980's. This is a critical fact that must never be forgotten in and attempt to use this work for predictive purposes. A moment's consideration of the dramatic changes in patterns, indicators and relationships often found in the data for other geysers reveals how tenuous this assumption may be.
Given this caveat, the following preliminary guidelines for forecasting major eruptions of Steamboat are suggested:
Indications that a major eruption is unlikely. There are many patters that suggest that the likelihood of a major eruption within the next 24 hours is very low. These include:
2) The occurrence of a Back Basin or basin-wide disturbance. Their effect on Steamboat was observed as far back as the 1970's [Hirschmann 1978], and this pattern has held true. Particularly "bad" indicators seem to be strong boiling or turbidity in Emerald Pool, and irregular activity in Echinus Geyser. These signs of a disturbance in the vicinity of Steamboat appear to be reliable indicators that Steamboat will not erupt soon.
3) Erratic and rapidly shifting styles of minor play, no matter how powerful. This is garbage function. No majors have been observed which were immediately preceded by this sort of activity.
Major eruptions have taken place during times when garbage function play dominated, but there are no data of descriptions of the type of play which occurred just before these majors. Even if it is assumed that majors can launch from garbage function without warning, eruption intervals at these times are typically several months. Thus, it is probably a good estimate that when this type of play prevails that chance of a major eruption in the next 24 hours is no more than one percent, and probably much less.
4) Well defined north or south function play. Given the apparent need for the minor play to progress to simultaneous function before a major can take place, the chance of a major in the next 24 hours during these times is probably less than 5 percent. However, during active periods with short eruption intervals these functions should be monitored regularly (at least every 24 hours) to detect a possible change to simultaneous function. This is especially true when south function play predominates.
Indications that a major eruption may be likely. There are far fewer of these. They are absolutely predicated on a time series of observations. They cannot be identified from a single observation of data point.
b) The absence of any evidence of a disturbance.
c) A observed of strongly inferred progression through north and south function (as defined above), with or without an intervening regression from south to north to south. "Strongly inferred" means that one of the functions may not have been observed, but was likely to have occurred in proper sequence while no observers were present. For example, on day 1 no play id observed, on day 4 south function was observed, and on day 6 simultaneous functions in observed. It is likely that north function occurred around day 2 or 3, but was not observed.
d) The presence of a well defined simultaneous function.
Based on observations in 1982, when all four of these criteria were met the probability of a major eruption in the next 24 hours approached 50 percent, and an eruption in the next 100 hours approached 90 percent.
2) The specific progression of factor scores observed in 1982 and 1984. the criteria for this condition are:
b) No persistent evidence of a disturbance, though one may have occurred since the last eruption.
c) The following progression of factor scores [defined in math analysis section of the article, not reproduced here]: a persistent period of scores near zero, followed by: a sharp rise of F2 to > 2.0 with a concomitant drop of F1 to < 0.0, followed by: a sharp rise of F1 to > 2.0 with F2 remaining above 2.0.
When data has been collected that demonstrates this progression of events, the likelihood of a major eruption in the next few days may approach 50 percent or higher.
One of the greatest difficulties with either of these methods is the time involved in gathering the data to ascertain the likelihood of an impending eruption. Most gazers have only a few weeks each year to enjoy geyser gazing; it is difficult to expect many of them to be willing to dedicate themselves to data collection during times when, according to these methods, the chances of an eruption are negligible. Nevertheless, is is the progression over extended periods of time of changes in activity that makes these models useful.
It is most likely that the only situation which will spur sophisticated gazers to dedicate the time to the study of Steamboat is the resumptions of short interval eruptions. When (or if) this occurs, the boardwalks and platforms near Steamboat will no doubt be packed with interested observers, including the authors.
A POSSIBLE CAUSE OF THE FUNCTION CHANGES OF STEAMBOAT GEYSER .... [Educated speculation as to the cause of the function changes.] ....
ACKNOWLEDGMENTS. Thanks go to the many observers during the years 1982-1984 who kept vigil at Steamboat and who provided us with data during times we were not present. These include Grover Schrayer, Dave Scheel, Rick Hutchinson, Jen Hutchinson, Fred Hirschmann, Cheryl Bleothe, Tomas Vachuda, Milada Vachudova, and Dave Leeking. Rocco Paperiello's extensive contributions to the understanding of the Echinus-Steamboat-Emerald fracture is noted and appreciated. Lee Whittlesey's monumental study, "Wonderland Nomenclature: A History of Place Names in Yellowstone National Park" (available through GOSA), was considerable help.
REFERENCES
Bryan, T.S., The Geysers of Yellowstone, Colorado Associated University Press, 1986.
Crellin, J., Letter to B. Lewis dated September 10, 1964, published in The Naturalist, The Naturalist History Society, 1979.
Day, J., personal communications, 1989, 1990
Hague, A., Norris Geyser Basin and Gibbon River Thermal Areas, unpublished manuscript, n.d. about 1915.
Hirschmann, F., informal communications, 1978-1982. The maximum height of Steamboat's water column has been the subject of discussion. In 1979, Hirschmann showed S. and P. Strasser a photograph taken of the August 23, 1978, eruption by a Naturalist (name not known). The type of lens used to take the photograph was known, as was the site of the photograph. By means of simple mathematics the highest droplets in the photograph were estimated at 450 feet (+/-40 feet).
Hutchinson, R.A., personal communication, 1984.
Lewis, B., personal communications, 1982.
Paperiello, R., personal communications, 1984-1985. The term "mini-zap" used to describe minor disturbances along the Cistern-Steamboat-Emerald Spring line was coined in 1984 by several gazers. Several other terms have been used to describe disturbances, including "grand mal" to describe major disturbances, and the inelegant "gibble" and "fargozzle" to describe the minor and major effects on Steamboat. More recently, "mini-zap" and "grand mal" have grown into accepted terms.
Paperiello, R., Report on the Norris Geyser Basin for 1984, unpublished manuscript (available through GOSA), 1988.
Paperiello, R., personal communications, 1989.
Pulliam, B., The Hundred Meter Sput, unpublished manuscript, on file at the YNP Research library, 1984.
Pulliam, B., personal communications, 1985.
Pulliam, B., new analysis of 1982/1984 minor activity of Steamboat Geyser, unpublished letter, 1989.
Strasser, P., Observations of Steamboat Geyser, Yellowstone National Park, unpublished manuscript on file in the YNP Research Library, 1983.
Strasser, P., notes on the behavior of Steamboat Geyser, unpublished letter, 1984.
Strasser, P., Strasser, S., Vachudova, M., visual inspection of Steamboat complex, 1985.
Strasser, P., personal communications, 1985-1989.
Vachuda, T., personal communication, 1983.
Weed, W., field notes, National Archives, RG 57, Box 56, vol. 1, *3899-A, p. 36, 1883.
Weed, W., field notes, National Archives, RG 57, box 47, Vol. 10, #3841, pp.110-111, 1885.
White, D.E., Hutchinson, R.A., and Keith, T.E.C., The Geology and Remarkable Thermal Activity of Norris Geyser Basin, Yellowstone National Park, Wyoming, U.S. Geological Survey Professional Paper 1456, 1988.
Wolf, M., personal communication, 1978.
Wolf, M., Report on Fantail and Ouzel Geyser, GOSA Transactions, vol 1., Yale University Press, 1989.
Photographs by P. Strasser.
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