[WIP] Looking for feedback on geological feasibility

[swiss]

This is a base map that I plan to redo in Photoshop. Am I doing anything geologically impossible regarding the mountains, lakes, rivers, and deserts here? Anything else stand out as wrong or missing?

[Ghostman]

That narrow strait where two rivers end almost head to head looks, not impossible but super unlikely to form naturally. Also regarding desert placement, if the assumption here is that they are due to rain shadow from the mountains, then why doesn't that apply to the range west of the middle desert?

[swiss]

This is the kind of feedback I was looking for! Yeah, you caught me on the rivers meeting at the strait. That was the one thing I put in there mostly because I thought it would be cool, rather than something I thought would form naturally. I talked myself into it saying the land on both of those peninsulas are raised up high from the ocean with cliffs and this river carved out a spot between them.

As for the missing desert, are you talking about this area in red? If so I figured that area could get rain from the ocean directly Southwest of the red circle. No?

[Ghostman]

Rain shadow mostly depends on the prevailing winds, which would be blowing about the same direction along the same latitude.

[waldronate]

It's tough to say much about plausibility without an understanding of the scale of this map. Is it ten miles across? A hundred? A thousand? Each of those scales has somewhat different results for plausibility. This statement is especially true for the desert area, which doesn't really have a natural reason to be where it is for most scales unless there are specific wind conditions and particularly talk mountains upwind.

One thing that catches my eye is that you like to run rivers down the lengths of peninsulas. Water always takes the shortest path downhill. If you want to have a river flow along a coastline (see the Nile river in Africa) then you will need to provide a valley for the river with hills between the river and the coastline.

[swiss]

It's tough to say much about plausibility without an understanding of the scale of this map. Is it ten miles across? A hundred? A thousand?

1500 miles across, 750 miles down

One thing that catches my eye is that you like to run rivers down the lengths of peninsulas. Water always takes the shortest path downhill. If you want to have a river flow along a coastline (see the Nile river in Africa) then you will need to provide a valley for the river with hills between the river and the coastline.

Agreed. I tried to do that with the mountains, and the water flows in the middle of the mountain ranges on the coastlines. I think you're saying I probably need to add some more mountains/hills so the water can't run off the side?

[waldronate]

Having something to suggest that the rivers flow there for a particular reason might be nice. It might also be overkill depending on your intended audience. A rough line offset from the river to show that the river is running down a canyon would probably be the most that you'd need, if you need anything at all. Knowing that the map is intended to be most of the size of the continental US and knowing (from the specified size) that the mountains are just rough placeholders both suggest to me that the map might be workable as-is. I do recommend including a scale on the map is possible.

[JonathanCR]

Rain shadow mostly depends on the prevailing winds, which would be blowing about the same direction along the same latitude.

It depends on the climate though. If it's tropical, more or less, there will be monsoons, which don't follow the prevailing winds but blow from the sea into the interior of continents (and back again depending on the time of year) and then get disrupted by mountain ranges. So issues of this sort will be affected not merely by the scale of this map but by the latitudes it's set in.