Similar word to upheaval:

about-face, alteration, cataclysm, catastrophe, clamor, commotion, convulsion, disaster, disorder, disruption, disturbance, eruption, explosion, ferment, flip-flop, new ball-game, new deal, outbreak, outburst, outcry, overthrow, revolution, shakeout, stirring, switch, temblor, tremor, tumult, turmoil, turnaround, upturn