in snow precip a ti on a nd th erm a l in so la ti o n , whi ch ex plains th e recentl y observed g lacier-m ass loss (Arenillas a nd o th er s, 1992 ).Furth erm o re, Nla rtinez d e Pison and Arenill as Pa rra ( 1988 ) includ ed some glaciere ts in th eir ca ta logue. As th ese glacier e ts d o not h ave crevasse, th ey do not consid er th em as g laciers, a lth o ug h th ey are remn a nts of previous ones (e.g. Punta Z a rra glacieret). Lik ewi se, a report of th e Nlini stero d e Obras Pllbli cas y Tra nsportes ( 1992 ) on th e snow in th e Spa nish cordill eras in cl ud es some glaciers in th e Spa ni sh P yrenees with dime nsions simil a r to Gl acia r J ou N egro, such as th ose of Punta Za rra, Balaitu s a nd T aillon. All of th em, loca ted in th e western part of th e glac ieri zed area, are sma ll-size g lac iers wi Lh an a rea o f 2 x 10" m 2 . R ega rdin g thi ckn ess, Glacia r J ou Negro is thi cker th an th ose in that rep o rt, the rea l valu es reachin g 14 m a t some points. Th e presen ce of isol a ted g lacier ice in th e Pi cos de Europa is pro ba bly du e to its slower res ponse to recent clim a te cha nges du e to th e specifi c charac teristi cs of its loca ti on, a bove 2200 m and with a north eas t as pec t a nd a shad y topogr a ph y, as it occ upi es an impo rta nt karsti c d epress ion. Future research co nce rning th e stage of evo luti on is pl a nn ed and this includ es th e m eas urem ents of poss ible va ri a ti ons in ice thi c kn ess and in g lacie r ex tent, as well as m odifi ca ti ons to th e wa ter-condui t sys tem.
ACKNOWLEDGEMENTFi eld assista nce a nd to pogra phi c wo rk, carri ed o ut by J.Al onso PCl'i a, is g ra tefull y ac kn ow ledged by th e a u th ors.Federacioll Asturiana de r..speleologlo,