<div dir="ltr">No, this isn't an attempt to be a smart aleck, and it is definitely not a newbie question either. Rather, it's a thing that arose from a very interesting conversation as I was researching an article I'm writing for the Sput, and a question for which I had no fully satisfying answer.<div><br></div><div>The article I'm writing is on the subject of geyser-like fountaining at volcanic crater lakes -- specifically, a "geyser" that I had the opportunity to observe a few years ago as a member of a research party working on a particular volcano that I won't name here. (This is called a narrative hook; read the article when it comes out.) To help with assembling a reference list, I had a conversation with a world-class expert on hydrothermal phenomena at active volcanoes, an expert who happens to be my son Peter, a Ph.D. student in volcanology whose thesis topic -- I oversimplify -- is the movement of ground water in response to magmatic incursions at awakening volcanoes. He was a member of that research party (nice to do father/son things like that!) and is well acquainted with the event, and posed the subject question; more specifically, he posed the question "and the thing we saw differs from what we call a 'geyser' in what way?" And I realized I had no good answer for him.</div><div><br></div><div>There are certain things we usually exclude from the definition of "geyser" even though they throw water and other stuff into the air: man-made wells and other artificial structures, cold-water springs where the water is propelled by carbon dioxide or other gases, and so on. However, things get ticklish when talking about two-phase ejection of water from a geological system as a result of interactions of ground water with a magma body with unknown mechanisms not necessarily relating to water flashing to steam beneath a constriction. That's the semantic space we're in with this article, and there are several practical reasons for exploring it.</div><div><br></div><div>Any thoughts on this from this august body of gazers assembled? All opinions appreciated.</div><div><br></div><div>-- Bill Johnson</div></div>