instantaneous...
Have you ever seen the damage done by the rainfalls flooding the washes in the desert? A 10 mile wash can alter its path and cut a new one in one single heavy storm.
If a few previous small rain storms have pushed some brush and soil into a bend, partially blocking the original route, when a seriously heavy rainstorn comes down the wash it will cut a new path and maybe a mile later rejoin the original route.
An instantaneous and violent tilt of the axis of the earth would probably cut multiple Grand Canyons. Moving such a massive amount of water over the soft bed of the ocean would rip the silt from the ocean bed doing more damage (creating Grand Canyons) than recent tsunami waves in Japan.
Now if it occurred slowly, say over a decade then the ocean bed would remain in place.
Is that logical to you or doesn’t it fit into a preconceived idea that you have?