The phrase "great upheaval" refers to a major and sudden disruption or disturbance. It indicates a significant and often chaotic event that causes significant changes or upheaval in a situation or society. Full definition
The 1800s were also a time of great upheaval in the United States, and Aptowicz ably places Mütter's life, not just in the context of some of the important changes in the practice of medicine (early versions of anesthesia made their appearance during Mütter's career), but also against a larger historical backdrop of slavery and the Civil War. (bookbrowse.com)
Feebee, my first cat and the love of my life for almost sixteen years, who got me through a period of great upheaval in my life in the mid-90's when my marriage of thirteen years ended and my mother died, all within a four month period, developed bladder stones (most likely, as a result of trying to absorb some of my stress). (consciouscat.net)
In my view, this has caused great upheaval and uncertainty among Indigenous people and communities, and even among the bureaucracy tasked with implementing the changes. (humanrights.gov.au)