How often does earth magnetic. field change dirrection?

That is much less often than in the last 150 million years, when the field has flipped every 600,000 years. In the last 10-20 million years it has sped up even more, to once every 200,000-250,000 years. "The evidence points to a more stable field in the very far past and fewer reversals," says Veikkolainen.

Every 600,000 years

Hope this helps

b.

developed countries have tended to improve the environment, while developing countries have tended to damage it.

the mediterranean sea