in this discovery channel episode, they said that when the poles change, the earths crust will move over the mantle and cause a Catostrophic event ending all life on this planet. But in High school, i learned that the mid altantic ridge, as it seperates on the ocean floor, it saves the polarity into the rock. And over the sea floor, you can see that the polarity has changed several times. What i'm wanting to know, is if the earth's poles has changed so many times in the past, why would it be catostropic this time?? I know there has been a seriers of mass extinctions in the past, but is this really what will happen??