[KittenClaws]

The map is interesting showing the subsistence is along the general valley

One wonders if the valley is not the result of long term subsistence

Then there is the south end where the contour lines nearly merge. that means a sharp gradient but I can’t interpret what means. Something important seems to be in process in that region
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Take a look at the San Andres fault line in that area. I'd post a pic, but I'm at work.

[ProtectOurFreedom]

Not fault related.
San Andreas is quite a ways west from that part of the county. It’s the alluvium.