▁presence ▁of ▁large ▁ju ven ile ▁blocks ▁identify ▁it ▁as ▁a ▁py ro cl astic ▁flow . ▁One ▁block ▁in ▁the ▁flow ▁and ▁the ▁la va ▁d ome ▁from ▁which ▁the ▁flow ▁origin ated ▁have ▁been ▁dated ▁at ▁ 0 . 6 ▁my a . ▁L ava ▁flows , ▁mostly ▁from ▁the ▁sum mit ▁areas , ▁are ▁dark ▁to ▁grey ▁in ▁colour ▁and ▁extend ▁as ▁far ▁as ▁ ▁from ▁their ▁v ents . ▁It ▁is ▁likely ▁that ▁two ▁small ▁la va ▁dom es ▁( C er ro ▁C um bre ▁Neg ra ▁and ▁Sum mit ▁ 5 8 6 7 ) ▁on ▁the ▁north west ▁fl ank ▁occup y ▁fl ank ▁v ents . ▁To ▁the ▁north ▁lies ▁the ▁ 3 . 3 ▁my a ▁old ▁and es ite ▁Cer ro ▁T res ▁Mon os ▁r idge ; ▁to ▁the ▁west ▁lies ▁the ▁east - west ▁Cer ro ▁Pol an ▁and ▁La ▁L una ▁r idge . ▁ ▁The ▁vol can ic ▁cluster ▁of ▁which ▁A uc an qu il cha ▁is ▁a ▁part ▁contains ▁about ▁ 1 9 – 2 0 ▁vol cano es ▁and ▁has ▁generated ▁about ▁ ▁of ▁and es ite ▁and ▁d ac ite ▁over ▁eleven ▁million ▁years . ▁Cover ing ▁a ▁surface ▁area ▁of ▁, ▁the ▁cluster ▁is ▁surrounded ▁on ▁its ▁northern , ▁western ▁and ▁eastern ▁sides ▁by ▁salt ▁fl ats ▁and ▁all uv ial ▁depos its . ▁On ▁its ▁southern ▁side ▁lies ▁the ▁Cer ro ▁Ch ela ▁vol cano . ▁The ▁cluster ▁lies ▁on ▁a ▁ ▁thick