Rgvedic RbIsa

[Jan E.M. Houben]

One of the numerous problematic terms in the RV is RbIsa (.rbiisa), which
occurs only four times: 1.116.8, 1.117.3, 5.78.4, 10.39.9. The context is
always similar: Atri enclosed in it, and there is help by the Asvins.
arvISa in JB 1.151 seems to have a similar meaning.
After the RV, RbIsa occurs in Zrauta-sUtras, e.g. kZS, and ApZS 5.25.6,
where commentators explain it as "fire hiding in coals". This is also
sAyaNa's explanation of the Rgvedic occurrences. In PW, however, we find
for the Rgvedic occurrence: "Erspalte, Schlund (aus welchem heisse Daempfe
aufsteigen)" and thismeaning is echoed in many later works, e.g. MW, and
in Kuiper 1955 ("volcanic cleft") where he quite justifiably lists the word
as one of non-Indo-European descent (cf. dental s after i).
My question concerns not so much the possible etymological connections of
RbIsa with words of non-Indo-European Indian languages, but rather the set
of possible referents of the term, more specifically whether at all there
are (or were in the last few millennia) any "vulcanic clefts" or "chasms in
the earth, from which hot vapours arise" in the Rgvedic geographical area
(North-West India, Pakistan, Afghanistan). So far the nearest vulcanically
active areas I could find on the map are at more than 1000 km distance from the
Rgvedic area, viz. south of the Caspian Sea and Indonesia.
I did see caves in India, but no "naturally heated" ones (nor did I hear of
their existence). Is the "vulcanic cleft" just the imagination of scholarly
recluses who were not (/insufficiently) acquainted with the area?

Jan E.M. Houben
Department of Languages and Cultures of South- and
Central Asia ("Kern Institute")
P.O. Box 9515
2300 RA   Leiden