Lots of examples where they are not correctly tagged when we talk about geology.

Should I edit the posts to correctly classify the info?

The trouble I see is my editions would need to be reviewed and some ancient questions will appear at active list if I review them.

I wonder too if I should add tags that are deduced from the answer and not from the question. (Imagine "What is this? I tag is as geology "It is a rock, then tagged as petrology too).

I've reviewed the tagging of the questions I've answered a few time and I do find annoying that all those questions get bumped to the top of the active questions list.

In Meta I saw other people complaining about the same thing, but it seem like the people behind SE thinks that is a desirable behaviour. And to be fare is not a big deal.

I would suggest that you go ahead with all the retagging you find is necessary, ideally doing it in very large or very small batches. If you do a lot of questions in one go you will monopolize the list of active questions just a few times. On the other hand, if you do it just a couple question at a time. It would be a nice way to boost the activity of the site and it won't bury other questions too deep in the list.

I will follow Camilo Rada's advice and only review 3 questions each day not to monopolize the list of active questions and not to flood the review queue.