By"concealedexplosionofmagma",wemeantheexplosiveproessofmagmaundersubterraneanconcealedconditionswhichisessen-tiallysimilartovolcaniceruptionseenatthesurface;theonlydiffer-"nceisthatthelattertakesplaceinanopenenvironmentatthesurface’`vhiletheformertinasemi-openenvironmentbelowathincovernearlhesurfac