This is going to come down to semantics, even more so than the question of series. The term was originally applied to Giant by George Marler, because during "hot periods" the temperature of the water in Giant's cone increased by a few degrees. The increase in water level and activity by the platform vents was incidental. The term got moved to Fan and Mortar by analogy to Giant--not to the temperature change, but to the geyser activity that accompanied it. Now it seems that any variation in activity associated with an increased likelihood of an eruption is at least informally termed a hot period. Well, some geysers erupt with absolutely no observable variation in activity prior to the eruption. Artmesia maybe (I'm not going to argue variations in its continuous bubbling), and Jet, to name a couple. On the other hand: Grotto's system has cyclic rising and falling water, along with boiling in Grotto Fountain prior to eruptions. Riverside has massive overflows with surging, followed by drops and lulls, while building up to an eruption. Great Fountain's water rises and falls, sometimes even with false overflows, until the overflow leading to an eruption. Beehive and Lion have been observed to have periods of frequent splashing alternating with periods of quiet (I've heard these referred to as hot periods), while building up to an eruption (an initial, in the case of Lion). Giantess has times when it has a lot of rim boils, and times when its completely placid. Hot periods? Depression and Oblong periodically overflow until an overflow leads into the eruption. Link has minor eruptions every couple of hours except right after a major. Rarely, it has a major instead. Since the term has become completely divorced from its original meaning, I suppose it _could_ mean any of these and more. The fact is, though, that there's a continuum of pre-eruptive activity, varying from no discerible change right up until the eruption, to minor variations in flow or water level, to distinct surges and ebbs, to periodic splashing or minor eruptions, all the way to the complex, system-wide, periodic minor activity we see in Giant and Fan and Mortar, sometimes for months or years between eruptions in the latter case. Where you choose to draw the lines between "minor fluctuations," "hot periods," and "minor eruptions" seems completely arbitrary to me. David Schwarz <div class="gmail_quote"> On Sat, Jul 4, 2009 at 10:56 AM, Davis, Brian L. <<a href="mailto:brdavis@iusb.edu">brdavis@iusb.edu</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Along the lies of "which geysers have series" (and what the definition of a series is as opposed to "bursts", etc.), which geysers have "hot periods", and how well defined are these? I can think of the Giant system and Fan & Mortar, but how many others could be characterized this way? One thing I'm trying to come to grips with is the energy balance in such system, and how much must be dissipated during a "hot period" compared to a full eruption. Or, when does a "hot period" get called a "minor"? -- Brian Davis _______________________________________________ Geysers mailing list <a href="mailto:Geysers@lists.wallawalla.edu">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>