al ▁B - T m ▁ash fall ▁att ains ▁more ▁than ▁ 5 0   km 3 . ▁A ▁low ▁total ▁bulk ▁volume ▁estimate ▁is ▁ 7 0   km 3 . ▁Horn ▁and ▁Sch min cke ▁( 2 0 0 0 ) ▁used ▁an ▁exponential ▁method ▁for ▁minimum ▁area / thick ness ▁and ▁maximum ▁area / thick ness ▁to ▁obtain ▁the ▁volume ▁of ▁the ▁Pl in ian ▁ash fall ▁as ▁ 8 2 ▁ ± ▁ 1 7   km 3 , ▁and ▁used ▁the ▁area - thick ness ▁method ▁for ▁ign im br ite ▁to ▁obtain ▁ 1 4 . 9 ▁ ± ▁ 2 . 6   km 3 . ▁The ▁total ▁bulk ▁volume ▁estimate ▁was ▁ 9 6 ▁ ± ▁ 1 9   km 3 . ▁Li u ▁et ▁al ., ( 1 9 9 8 ) ▁also ▁used ▁same ▁method ▁with ▁Horn ▁and ▁Sch imin cke ▁to ▁calculate ▁the ▁volume ▁of ▁Pl in ian ▁ash fall , ▁and ▁obtained ▁the ▁similar ▁value ▁of ▁ 8 3   km 3 . ▁However , ▁Li u ▁used ▁a ▁different ▁area - thick ness ▁value ▁for ▁ign im br ite . ▁Li u ▁assumed ▁a ▁distribution ▁of ▁ign im br ite ▁within ▁ 4 0   km ▁of ▁the ▁cal der a , ▁and ▁an ▁average ▁ign im br ite ▁thick ness ▁of ▁ 7 . 4 7 m , ▁yield ing ▁a ▁volume ▁of ▁ign im br ite ▁of ▁ 3 7 . 5   km 3 . ▁The