upheaval noun

ADJ. big, enormous, great, major, massive, violent | domestic, economic, emotional, political, social The loss of his high-paying job caused enormous domestic upheaval. | revolutionary

VERB + UPHEAVAL cause, provoke | go through, undergo The company underwent a massive upheaval after the takeover.

PREP. during/in the ~ He rose to power during the political upheavals of the 1990s.

PHRASES a period of upheaval