I'll respond to provide a potential trump to the technical discussion which will surely follow this question. The brief answer is when the minor events "go real high at the same time in a sustained fashion." My addition to the conversation is that this is an extremely ill-defined phenomenon. People who have seen many "locks" still miscall locks. That's just because the geyser reserves the right to do what ever it wants. The word "lock" implies that it now must erupt: clearly false. No matter what anyone says, it can look great and do nothing, or look terrible and erupt 2 minutes later. The former is much more common than the latter. To greatly summarize a large body of empirical experience, when people have been excited about F&M, you want to be there by about 10 min. after Gold starts. If I'm there, you can join me watching it not erupt. ________________________________ From: Bob Mabery <bmabery at gmail.com> To: geysers at lists.wallawalla.edu Sent: Thursday, August 18, 2011 3:37 PM Subject: [Geysers] F&M - What's a "Lock"? I read with interest the detailed descriptions of the varied cycles of Fan and Mortar. Is there someplace that I can read a definition of the elements of the cycle, perhaps with photos? For example what is a "lock?" BobInGA W4YBB "Your Buddy Bob" _______________________________________________ Geysers mailing list Geysers at lists.wallawalla.edu -------------- next part -------------- An HTML attachment was scrubbed... URL: </geyser-list/attachments/20110818/d8305b3f/attachment.html>