<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:st1="urn:schemas-microsoft-com:office:smarttags" xmlns="http://www.w3.org/TR/REC-html40"> <head> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii"> <meta name=Generator content="Microsoft Word 11 (filtered medium)"> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"/> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"/> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PersonName"/>  <style>  </style>  </head> <body bgcolor=white lang=EN-US link=blue vlink=purple> <div class=Section1> FYI, I’ve measured a ton of Grand eruption heights.  I don’t know who told you that they’re 150 to 180 feet, but unless there is some big change recently, most eruptions aren’t that high.  Yeah, the books say they are, and the sign says that they are, so… voila – they must be that tall.  They aren’t. <o:p></o:p> <o:p> </o:p> The average max height of those I’ve measured about 15 years ago is about 145 feet.  I’ve never measured one 180 feet high, although I’ve seen a few “holy COW!” eruptions over the years that could easily have been 200 feet, and I have a poster on my wall of an eruption that I saw in 1978 that was easily in the 190+ range… but I didn’t measure it officially.<o:p></o:p> <o:p> </o:p> <o:p> </o:p> But on average?  145 or so.  In fact, this year’s eruptions seem rather low for the most part.<o:p></o:p> <o:p> </o:p> Easiest way to measure/guesstimate:  Go to the place where the boardwalk splits around Belgian Pool.  It’s very close to 200 feet from the Grand vent there.  Imagine a 45 degree angle.  That’s 200 feet.  How many times do you see it that high??? Hardly ever.  <o:p></o:p> <o:p> </o:p> I believe the boardwalk, at its closest to Grand, is about120 feet away (I’m not quite sure about this…).  That means a 45 degree eruption from there is – tah-dah – 120 feet high.  Suddenly, all those “150 to 180 foot tall” eruption claims seem a bit smaller.  I take that back --- they seem a LOT smaller.  <o:p></o:p> <o:p> </o:p> The way I and most other gazers who actually measure heights of the major geysers, is to go to a recognized, measured benchmark and use a clinometer, usually by Suunto, to get a reasonably accurate height.  After a while, like measuring a couple hundred eruptions, I got pretty good at eyeballing them.  <o:p></o:p> <o:p> </o:p> The funny thing is, though… no matter what number someone arbitrarily sticks on an eruption (I once heard a naturalist, who is no longer at OF, say that Grand commonly erupts to 360 feet), the geyser erupts as tall as it does, no more and no less.  Frankly, your instincts of slightly underestimating its height are smart.  Some people desperately want to hear that the beautiful eruption they just saw was some “standard” that they expect, like 180 feet or whatever.  <o:p></o:p> <o:p> </o:p> BTW, two of the tallest Grand eruptions I’ve ever seen have occurred in the last couple of years.  Also some of the puniest.<o:p></o:p> <o:p> </o:p> Paul Strasser<o:p></o:p> <o:p> </o:p> <div> <div class=MsoNormal align=center style='text-align:center'> <hr size=2 width="100%" align=center tabindex=-1> </div> From: geysers-bounces@wwc.edu [mailto:geysers-bounces@wwc.edu] On Behalf Of John Taliaferro Sent: Monday, June 18, 2007 10:21 AM To: <st1:PersonName w:st="on">geyser observation reports</st1:PersonName> Subject: [Geysers] Eruption Height<o:p></o:p> </div> <o:p> </o:p> <div> Thanks to those gazers who put up with my lame questions during my initiation into earnest gazing on 14-15 June. Everybody has firsts, and mine were marvelous: Grand (twice), Daisy, Castle, <st1:City w:st="on"><st1:place w:st="on">Riverside</st1:place></st1:City>, and Lion, to name the high points. Among the many things my untrained eye had trouble evaluating was the height of any given eruption. For instance, I guestimated Grand's bursts at roughly 100 feet. I was informed that they were at least 150, perhaps 180 feet high. Question: Is there a recognized technique for measuring eruption height without relying on actual instrumentation? How do you guys do it -- or is it best not to try? Thanks. John Taliaferro <o:p></o:p> </div> </div> </body> </html>