Saying a Beracha on a River Formed After Creation

Just a quick interesting halachic issue I found. Everyone knows that on a large impressive river, one says the beracha "oseh maaseh bereshis". However, what I didn't know was that there is a condition on this beracha:

According to Artscroll Yerushalmi Berachos 88b1-2 footnote 11, the Pri Megadim to Magen Avraham says that one may NOT recite the beracha of "maaseh oseh bereshis" on a river unless the river has always been there since the time of Creation. I.e. if there was a large earthquake/volcano/atom bomb that caused a new river to form today, then we would not say the beracha upon seeing such a "new" river. Also, if we purposefully change or add to a river (like a canal), then we cannot say the beracha on the new part of the river.

The question arises that if one holds like the authorities (mostly kabbalists) that say that the world is very ancient (on time scales like those that scientists have determined), then it is possible that we could never say this beracha. Since according to geologists, the Earth has gone through huge changes over time, any river we see today is likely not to have existed in the distant past. (For example, during the ice ages, and especially during the gathering of the first water on Earth).

It would seem one would have to say that the Creation is not considered truly completed until Adam Harishon was formed. According to that, (and the opinions that the world simply looks old but in reality is only as old as the time of Adam Harishon), we would need to determine if any particular river was around for the last 6000 years before we could say a beracha upon seeing it. It would be interesting to see if it is halachically permissible to use the findings of geologists to make such determinations.