TODO: There is no consensus on what we should do here. Needs discussion
RP: make something up, put it on the wiki.
natural=fumarole is more than adequate
HB: wiki page created.
Glen wrote: +1 for natural=fumarole. We can tag it as that and wait for the
proposals to work its way through eventually.
HB: I wouldn't really hold my breath for the Icelandic contingent and the
Yellowstonians to join in, but the proposal is in place now & so tagging approved.