<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=US-ASCII"> <META content="MSHTML 6.00.2900.2769" name=GENERATOR></HEAD> <BODY id=role_body style="FONT-SIZE: 10pt; COLOR: #000000; FONT-FAMILY: Arial" bottomMargin=7 leftMargin=7 topMargin=7 rightMargin=7><FONT id=role_document face=Arial color=#000000 size=2> <DIV> <DIV>In a message dated 11/30/2005 5:15:13 PM Pacific Standard Time, riozafiro@comcast.net writes:</DIV> <BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>Scott, or anyone...just how rare is a "no significant disturbance year"?<BR>Thanks,<BR>Pat S.<BR></FONT></BLOCKQUOTE></DIV> <DIV></DIV> <DIV>This isn't all that easy to answer, but the following is known:</DIV> <DIV> </DIV> <DIV>1. The first record of a (probable) disturbance was in 1878.</DIV> <DIV>2. Disturbances have been recorded in not fewer than 77 years since 1878 (so in 78 years, total). Apparently, though, it was not until the disturbance of 1926 that details were recorded (by Phillips). Records that cite any Norris activity were extremely sparse during the first 50+ years of Yellowstone history.</DIV> <DIV>3. USGS/NPS (most specifically in USGS Professional Paper 1456) notes the disturbances as "almost with annual frequency."</DIV> <DIV>4. There have been some years in which disturbances repeated several times in a single season.</DIV> <DIV>5. Some disturbances have affected ALL of Norris (Porcelain, Back, 100 Springs, and even Elk Park) -- including that of 1974 which PP1456 (read, Hutchinson [sorry, but true] ) stated "details not recorded." See Transactions VII.</DIV> <DIV> </DIV> <DIV>Well, anyway -- it seems that a year without a disturbance is indeed unusual.</DIV> <DIV> </DIV> <DIV>I should note, too, I suppose, that the official term for this (I guess it's official, since it is used in PP1456) is "Widespread Contemporaneous Changes." Yuk.</DIV> <DIV> </DIV> <DIV>Scott Bryan</DIV></FONT></BODY></HTML>