If I'm understanding what you're referring to as "obvious changes" correctly, I believe that very little actually changed between those photos (and even between 1883 and the present day), and the apparent difference is actually an illusion created by the view and lighting of the 1883 photo. Here's a photo from barely a year later (1884 or 1885) that shows the cone from a more familiar angle: <a href="http://www.flickr.com/photos/beinecke_library/2680801218/in/set-72157606240858888/">http://www.flickr.com/photos/beinecke_library/2680801218/in/set-72157606240858888/</a> The "left" (north) rim of the cone abruptly drops off by 3/4 of its height as it curves around to the "front" (left and front with respect to our current view of the geyser from the boardwalk). The 1883 photo is taken from a location a little more around to the left side of the geyser than the 1884 photo linked above. The low part of the "left" rim happens to align with the base of the familiar "bite" on the right rim, and makes it appear that the left and right rims are connected. I doubt very much that they actually were. The main change between the 1883 photo and the current state of the feature is a bit of erosion. The whole cone appears more weathered, probably due to its long period of inactivity, during which the sinter likely dehydrated and was subject to freeze-thaw cycles. Also, a section came off of the top of the left rim of the cone in one of the recent eruptive series--I want to say in the early 2000s, but it might have been with the 1997 activity. That one I'd attribute to years of erosion followed by enough eruptions to push out the loosened slab of rock. It's nicely visible in this photograph: <a href="http://www.billhusler.com/Photos/Trips/19990814%20Yellowstone%20trip/Yellowstone/Geology/Y%20Giant%20Geyser.JPG">http://www.billhusler.com/Photos/Trips/19990814%20Yellowstone%20trip/Yellowstone/Geology/Y%20Giant%20Geyser.JPG</a> David Schwarz <div class="gmail_quote">On Sun, Sep 13, 2009 at 8:26 PM, David Monteith <<a href="mailto:dmonteit@comcast.net" target="_blank">dmonteit@comcast.net</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> From: Janet Chapple <<a href="mailto:jochapple@earthlink.net" target="_blank">jochapple@earthlink.net</a>> To: Geyser Observation Reports <<a href="mailto:geysers@lists.wallawalla.edu" target="_blank">geysers@lists.wallawalla.edu</a>> Subject: Fwd: Giant's Cone pictures Date: Sun, 13 Sep 2009 09:37:00 -0700 Hello gazers, I have often wondered about the evolution of the shape of Giant’s cone, and recently I’ve found two old photos to compare. The older one is from Sheridan, Lt. Col. M. V., "Journey through the YNP and Northwestern WY," 1883, and the other is a Haynes photo from Clyde Max Bauer’s 1937 book, "The Story of Yellowstone Geysers." What I’d like to know from gazers is whether someone could share with us a recent photo of the cone to compare with these, and if anyone knows whether the obvious changes have been made by the force of Giant’s eruptions or by vandals or perhaps by both. I apologize for the poor quality of the copy I made of the Bauer photo. Janet Chapple _______________________________________________ Geysers mailing list <a href="mailto:Geysers@lists.wallawalla.edu" target="_blank">Geysers@lists.wallawalla.edu</a> <a href="https://lists.wallawalla.edu/mailman/listinfo/geysers" target="_blank">https://lists.wallawalla.edu/mailman/listinfo/geysers</a> </blockquote></div>