ka id ō , ▁Japan , ▁next ▁to ▁Mount ▁U su . ▁ ▁The ▁mountain ▁was ▁created ▁between ▁ 2 8 ▁December ▁ 1 9 4 3 ▁and ▁September ▁ 1 9 4 5 . ▁ ▁Initial ly , ▁a ▁series ▁of ▁strong ▁earth qu akes ▁shook ▁the ▁area , ▁and ▁whe at ▁fields ▁were ▁rapidly ▁u pl ift ed . ▁ ▁L ava ▁broke ▁through ▁the ▁surface ▁and ▁the ▁current ▁peak ▁was ▁created . ▁The ▁peak ▁is ▁now ▁ ▁tall , ▁and ▁still ▁act ively ▁sm oking . ▁ ▁The ▁name ▁Sh ō wa - sh in zan ▁means ▁" Sh ō wa ▁new ▁mountain ", ▁as ▁it ▁formed ▁during ▁the ▁reign ▁of ▁Emperor ▁H iro h ito , ▁known ▁as ▁the ▁Sh ō wa ▁period . ▁ ▁When ▁Sh ō wa - sh in zan ▁first ▁appeared , ▁the ▁Japanese ▁authorities ▁were ▁wor ried ▁that ▁it ▁might ▁be ▁interpreted ▁as ▁an ▁un l ucky ▁w art ime ▁o men , ▁and ▁its ▁existence ▁was ▁kept ▁secret . ▁ ▁Much ▁of ▁the ▁information ▁about ▁peak ' s ▁formation ▁during ▁these ▁years ▁comes ▁from ▁local ▁post master ▁Mas ao ▁M im ats u , ▁who ▁kept ▁detailed ▁measurements ▁of ▁its ▁progress . ▁ ▁Vol can ic ▁activity ▁tim eline ▁Gener ally , ▁the ▁vol can ic ▁activity ▁of ▁Sh ō wa - sh in zan ▁can ▁be ▁divided ▁into ▁three ▁main ▁phases ▁as ▁recorded ▁by ▁Mas ao ▁M im ats u . ▁ ▁Ph ase ▁ 1 , ▁Pre - E ruption ▁Ph