You said, "everything you've been agreeing to suggests a slow Grand Canyon origin and a fast Martian canyon." I said I reject that idea.
... despite the fact that the Grand Canyon meanders and the Martian canyon doesn't. See, that's the problem.
Whatever caused the short wide bit would have had a tremendous impact on everything else under it.
And above it? The whole region has the same look to it. You just picked out the straightest bit, whose edges, I can't help but observe, are still pretty uneven.
It is my understanding that a large water source will start out strong and slowly taper off.
So
now you're saying that it was in fact the
same water source that caused both your "high velocity" short wide bit and the meandering Grand Canyon?
By the way, your little stretch is narrower "upstream," where the flow would have been stronger, than it is downstream (but still in the "high velocity" zone). Is that what usually happens? I'm not sure what to expect. This seems to me to be an awfully wide and low "rim" for a large volume of water to suddenly punch through.
Also, your figure cuts off an interesting bit of terrain. Go back and look at the region northwest of the top of your blue line. It rather strongly suggests that the high velocity water that you need to carve your short wide canyon made a nearly 90-degree angle turn just before it blasted through that "straightaway."
This piece of common sense explains both features we are referring to.
No, actually,
you need to do the explaining. That is, you need to take this piece of "common sense" and use it to explain the specific features of the region under discussion. Or regions, in this case. E.g., where's the Grand Canyon-like meander downstream of the Martian canyon that your common sense predicts?
The meandering features were formed by slower moving water. The wide and straight parts were formed by a large influx of fast moving water. In progressing from the large volume to the no volume we see today the flow of water also went from fast to slow.
Okay, I think we've reached some sort of limit here. It's not at all clear how your simplistic explanations could begin to account for the specifics of this situation, e.g. the length, breadth, depth, and complexity of the various regions (i.e., the short wide bit, the regions upstream from it, the Grand Canyon itself), their proximity, their angular arrangements, etc., nor does any of this justify your insistence that the same scenario (a short burst of lots of fast moving water) could produce such completely different results as the Martian canyon and the Grand Canyon region. But it's like pulling hen's teeth to get you to move beyond the "common sense says it should all work and it's silly to think otherwise" phase. How you think that this is a more rigorous approach than the actual gathering and explicit interpretation of data used by geologists in these cases is beyond me.
I do have a non-scientific puzzle, however. Though you haven't said so explicitly, this specific, local event with the vast amounts of fast-moving water is part of The Global Flood, right? If so, which end of the Flood are we looking at here: the
arrival of the Flood waters or their
departure?
