8 5 , ▁and ▁A . D . ▁ 7 3 0 . ▁Since ▁longer ▁dated ▁tree - ring ▁sequence , ▁fin er ▁sample ▁resolution , ▁and ▁higher ▁ ▁analyt ical ▁precision ▁all ▁facil itate ▁more ▁and ▁t ighter ▁tie - points ▁for ▁better ▁WM ▁d ating . ▁The ▁new ▁date ▁is ▁believed ▁to ▁represent ▁yet ▁the ▁best ▁high - ac cur acy ▁and ▁high - prec ision ▁ ▁WM ▁chron ology ▁for ▁the ▁Mill en ni um ▁er u ption . ▁X u ' s ▁wood ▁samples ▁were ▁cut ▁from ▁a ▁tree ▁growing ▁in ▁the ▁area ▁about ▁ 2 4   km ▁from ▁the ▁vent ▁of ▁Ch ang ba ish an ▁vol cano , ▁it ▁is ▁not ▁clear ▁if ▁vol can ic ▁CO 2 ▁emission ▁before ▁the ▁er u ption ▁could ▁affect ▁the ▁samples ▁and ▁produce ▁ages ▁that ▁are ▁slightly ▁too ▁old . ▁The ▁best ▁WM ▁dates ▁for ▁the ▁Mill en ni um ▁er u ption ▁use ▁the ▁out liers - rem oved ▁subset ▁of ▁the ▁original ▁ ▁measurements ▁and ▁also ▁account ▁for ▁the ▁effect ▁of ▁possible ▁regional ▁ ▁offset , ▁and ▁yield ed ▁two ▁nearly ▁identical ▁WM ▁ages ▁of ▁ ▁and ▁, ▁where ▁overall ▁and ▁combined ▁agreement ▁indices ▁of ▁the ▁models ▁reach ▁their ▁highest ▁values . ▁Therefore , ▁the ▁average ▁of ▁these ▁two ▁WM ▁ages ▁ ▁represents ▁the ▁best ▁mode led ▁WM ▁age ▁for ▁the ▁Mill en ni um ▁er u ption . ▁ ▁Historical ▁records ▁ ▁The ▁book ▁G ory e osa ▁( History ▁of ▁G ory e o )