(v)erupt, irrupt, flare up, flare, break open, burst outerupt or intensify suddenly“Unrest erupted in the country”, “Tempers flared at the meeting”, “The crowd irrupted into a burst of patriotism”
(v)crop up, pop up, pop, pop out, burst outappear suddenly or unexpectedly; happen unexpectedly“The farm popped into view as we turned the corner”, “He suddenly popped up out of nowhere”