Fill a cake pan nearly full with water and slide it sideways across the counter -- observe what happens. That's a pole shift.

Start with these videos and dig in to the other videos in those channels. the The first covers more of the global clues left behind while the second has a better handle on the physics and actual triggers. Every twelve thousand years. https://www.youtube.com/watch?v=-EAYgB07ZCE https://www.youtube.com/watch?v=WAlyvbt8Nlk There's that Ancient Apocalypse series on Netflix that covers remains of prior events too, although attributing destruction to asteroid impacts.