<HTML>http://www.seis.utah.edu/helicorder/heli/yellowstone/Uuss.YNR_SHZ_WY.2006091400.gif If you go to the link above, it should connect you to the Webicorder Display for Norris Geyser Basis for the 14 September 2006 chart.  My question to the experts of this group is:  What has caused the disturbance that is seen at 20:00 MST on this chart?  Is there a correlation to a geyser in eruption that would last 30 minutes and cause the seismograph to record such an eruption?     Just wondering.... Gary Henderson - Meridian, Idaho</HTML>