Seismic shift

The seismic shift in Mexico began in 1810 with the movement toward independence from Spain.

For the republican movement, the acceptance of seats in a "partitionist" Assembly signaled a seismic shift in historical attitudes since the division of Ireland in 1921.

[T]he U.S. could be on the verge of a seismic shift, where it is possible to envision a time when it will no longer be the dominant economic superpower.

Baby boomers began turning 65 in January, heralding a seismic shift in demographics worldwide.