Why does the Red River of the North flow south from the North/South Continental Divide at about the N/S Dakota border and the Mississippi whose headwaters are in Northern Minnesota flow south?
Thanks,
eddie460

asking

Water flows downhill. There's no more to it than that.

From where one river starts, the most direct downhill path is to Lake Winnipeg. For the other River, it's to the Gulf of Mexico.

River flow is contingent, so once the flow gets lower than a certain point, it will continue on that path. As a result, subtle differences in terrain at the headwaters (on a mountain) can put a river in a completely different drainage.

FlyYakker

Asking is correct, but the larger question might be"What geological forces so formed the area in question that the rivers flow as they do?".

asking

Just for fun, I'm going to argue. Maybe I'm nitpicking, but I'm not sure that's a larger question.

The current topography of an area will determine flow, but that topography is partly determined by uplift (yes, geologic forces generally), partly by the erosion caused by the flow itself. Water can cut through almost anything, given enough time. Anyway, I don't think there are specific geologic forces per se that explain why rivers that arise close together flow in different directions.

In other words, I don't think there are big rules that determine these things (other than water flowing down hill). Think of Jeff Goldblum dripping water on the knuckles of Laura Dern in Jurassic Park and having the water seem to go randomly on one side or the other. That's contingency.

There's a mountain in California that is the headwaters for three different major rivers. Of course, each of those three drainage systems gets major inputs from other rivers coming from other sources. But the mountain just happens to be the highest one around. Because it's high, it still has a glacier (rapidly shrinking) and so a year round supply of water. And (I think) because it's so high, its creeks end up being called the "headwaters" of whatever systems they feed.

FlyYakker

OH,SURE, here I am, old and puny and people want to pick fights with me. Well you have a point asking. Geology is not my forte', and I'll grant randomness initially. I also think, however, the randomness will be made less random based on the the geological features shaped by geological forces. Those forces (and I'm including here, however inaccurately, glacial forces, which I THINK were present in the area under discussion) also may have resulted in materials that were more, or less, easily eroded where the springs come forth, say.

asking

Hmm. Could be. So you are saying that a glacier might create mountains of debris, for example,that are more likely to let water flow through than solid rock?

I'm guessing our different perspectives may be due to neither one of us knowing much geology and also coming from different geographic areas. Glaciers in California cut nice round valleys in v shaped valleys and leave neat little debris piles on either side (lateral moraines) and at the end of the glacier (terminal moraines).

Aside from the occasional earthquake fault, everything flows through those neat valleys to the Pacific Ocean, one way or another, (or else into the Great Basin desert, where it evaporates).

Things may look really different up on the Canadian Shield, about which I know almost nothing.

I guess I don't really know what you are saying....

FlyYakker

Well, I was thinking Ice Age glaciers which were REAL earth movers - broad sheets of ice 3-4 kilometers thick expanding across the land and moving earth. See for example. Ice age - Wikipedia, the free encyclopedia . Hard to believe, but a good part of the Northern tier of states was affected by them. Not necessarily mountain builders (I think that is pretty much a plate techtonics thing) but land shapers.....

10-4 on not being experts. I'm winging it on the area under question being affected by glaciation, although I'm pretty sure it was. I keep waiting for a geology expert to put in a comment.