▁one ▁hill , ▁Cer ro ▁Camp ana , ▁dated ▁to ▁ 3 . 3 ▁my a . ▁The ▁platform ▁pres umably ▁forms ▁one ▁third ▁of ▁the ▁total ▁volume ▁of ▁the ▁A uc an qu il cha ▁cluster ▁and ▁may ▁have ▁origin ated ▁from ▁a ▁part ▁of ▁the ▁r idge ▁of ▁the ▁La ▁L una - Pol an ▁tr end , ▁now ▁buried ▁beneath ▁A uc an qu il cha . ▁Ch ai hui ri ▁( 2 . 3 9 ▁my a ) ▁is ▁a ▁la va ▁d ome ▁with ▁mor aines ▁and ▁two ▁short ▁la va ▁flows ; ▁it ▁is ▁the ▁young est ▁Pol an ▁group ▁vol cano . ▁The ▁total ▁volume ▁of ▁this ▁group ▁is ▁, ▁indicating ▁a ▁flux ▁rate ▁of ▁. ▁ ▁After ▁the ▁four ▁main ▁phases , ▁some ▁sc oria ▁con es ▁of ▁bas alt ic ▁composition , ▁including ▁Por u ñ ita ▁and ▁L una ▁de ▁T ierra , ▁formed ▁between ▁A uc an qu il cha ▁and ▁O ll ag ü e . ▁ ▁A uc an qu il cha ▁proper ▁▁ ▁The ▁main ▁A uc an qu il cha ▁vol cano ▁formed ▁in ▁four ▁stages . ▁Between ▁ 1 . 0 4 – 0 . 9 2 ▁my a ▁the ▁bulk ▁of ▁the ▁vol cano ▁formed ▁in ▁the ▁Az uf rera ▁stage . ▁One ▁la va ▁flow ▁toward ▁the ▁south west ▁is ▁unus ually ▁long ▁at ▁. ▁A ▁vent ▁at ▁ ▁alt itude ▁fed ▁most ▁of ▁this ▁ed ifice ; ▁a ▁second ▁vent ▁on ▁the ▁northern ▁fl