<html dir="ltr"> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <style id="owaParaStyle" type="text/css">P {margin-top:0;margin-bottom:0;}</style> </head> <body ocsi="0" fpstyle="1"> <div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">Jeff, I have never heard loud noises from ANY New Zealand geyser.  Certainly Lady Knox geyser, at Waiotapu, after its reliable water column stage, gradually subsides into a persistent but gradually declining steam phase with its noise then being describable only as a fluctuating soft "sighing" sound.   As communicated to you directly in another context, Pohutu Geyser at Whakarewarewa produces similar mild sound effects.  However, between 1892 and 1894 Rahurahu Geyser (alternatively called "Terrific Geyser"), at Orakeikorako, had a definite and very loud steam phase with individual eruptions continuing for between one and two hours.  At the time this was without doubt the most powerful geyser in the country and was eclipsed only by Waimangu in its heyday from 1900 to1904.  The ejections of both Rahurahu's water column and its following steam phase formed a jet at about a 45 to 50 degree angle to the horizontal.  The then Rotorua Engineer, Camille Malfroy, prepared an official report on the geyser. Its discharge seemingly was so steady that he was able to approach within a few feet of it.   "When what I call the seond phase of the eruption started - consisting of a jet of super-heated steam and water of a bluish-purple tint, and into which I could not thrust a pointed stick - the water emerged out of the fissure, and striking against the projecting rock, it was lifted up at an angle of about 45 degrees, throwing a fine spray a distance of fully 70 yards.  The terrific force at which the steam is ejected against the  rock, and its sudden expansion as it emerges out of the fissure, make a terrific roaring noise, which can be heard at a considerable distance, and it is with great difficulty that one can be heard to speak in the vicinity of the geyser."  Many more details, including reproductions both of a close-up and of a distant photograph, are given in Ted Lloyd's Bulletin "Geology and Hot springs of Orakeikorako" (1972).  Unfortunately Rahurahu geyser vent was submerged beneath Lake Ohakuri when this was impounded for the production of hydro-electric power in 1961.  In the1950s the vent was usually completely quiescent, but on just one occasion I did chance upon it discharging.  An attempt to stimulate it into more interesting behaviour by rapidly baling water from the pool was unsuccessful.  Neighbouring Minginui, which when I first saw it in 1951 was a a quietly simmering pool, developed into a boiling spring and later a geyser in the mid-1950s, and Ted reports that on 5 May 1954 two observers saw it erupting to a height of about 90 metres and that after 20 minutes "...this was followed by a steam period resembling in noise and output a geothermal bore at Wairakei."  The paucity of noisy steam phases in New Zealand cases leads me to wonder if the contrast with Yellowstone has to do with the significantly different specific volumes of steam at boiling temperatures in the two locations. The vent elevations in New Zealand are all around 700 to 900 feet above sea level, whereas at Yellowstone they are of course around 5000 feet. Ron Keam In assembling a list of geysers that have loud steam phases, I have wondered how far the sound of the steam phase carries. Previous posts on this list, together with literature sources, indicate that Steamboat is plainly audible at the Norris Campground (1.2 miles away), and that Giantess has been plainly audible at Riverside Geyser (0.9 miles away).  Similar figures can be obtained for other geysers.  However, I cannot find data for the following geysers: Bijou Catfish Atomizer Fantail Whistle Clepsydra (back vent) Ledge Dark Cavern Africa Union I ask if anyone has data, or can remember, how far away the steam phase of any one or several of the above geysers should be plainly audible? Thank you, Jeff Cross jeff.cross@utah.edu _______________________________________________ Geysers mailing list Geysers@lists.wallawalla.edu https://lists.wallawalla.edu/mailman/listinfo/geysers </div> </body> </html>