Caused by a 1 that cannot move a space when causing it but counts as a piece move. The one must be touching the volcano diagonally to cause the eruption. The Eruption destroys any adjacent piece (hor or vert) and freezes pieces within 2 spaces for 2 turns(hor vert and diag) by covering them with ash--applies to both black and white pieces. Frozen pieces cannot be revealed by recons until they thaw, but capture rules are the same as usual. Previously revealed pieces covered in ash are disguised again until revealed by recon...oh wait, that won't make a difference with piece moves tracked in the move list.