Do we prefer tags like this:
or like this:
I'm tempted to say the latter. This is (hopefully) a multidisciplinary site, and if I'm asking a question I may not know exactly what field it falls under... but I do know what physical feature I'm talking about.
Some physical features are relevant to multiple disciplines (e.g. glaciers might be relevant to geologists, climate scientists, oceanographers...) but I see that as a positive, encouraging serendipitous discoveries of cross-discipline questions that one might not otherwise spot.
I don't feel this very strongly, though, and I'm tempted to say "Wait a bit, see what naturally developers, then take a view and clean up" ;-)
I'm going to propose tags should follow the former spec:
I love that this site aspires to be an expert site. Don't be afraid of using grown-up expert tags, rather than kiddy-talk.
If you want a community of experts, then use that language, particularly in tags. By all means write accessibly. Technical language has the advantage of precision and a body of shared understanding about its meaning. Lay language (such as "caves") is messy, smeary, bleared and usually ambiguous.