[OokieWonderslug (OP)]

I have seen several videos claiming that there were two subduction zones that make up the Carolina piedmont. What I cannot for the life of me find is just where they are. Does anyone know? Or is that merely a theory people have of how the piedmont formed and not supported by direct evidence?

[evan_au]

subduction zones that make up the Carolina piedmont. What I cannot for the life of me find is just where they are

Perhaps you are looking for a dip in the Earth's surface?

Maybe you should be looking for mountains (like the Carolina piedmont plateau)?
- If there is a region of crust which is dropping (like the Mississippi basin is today), lots of sediment builds up in it.
- This sediment is crushed, heated and turned into rock - often with magma injected
- Later, when the crust stops dropping, this sediment is often pushed upward to build mountains and/or a plateau

I see from geological maps that there are several regions of plateau around there - maybe there were two different subduction events in different eras?

[OokieWonderslug (OP)]

As I understand it there was a line of volcanic islands off the eastern coast of the US. A subduction zone had the islands approach the coast and collide with it. Then later another subduction zone approached with Africa behind it.  Africa collided with the continent and made the Appalachians. Later Africa pulled away and caused basins to form in the East of NC which quickly filled with sediment. When Africa pulled away a large section of the mountains stretched and collapsed forming the Blue Ridge and the Piedmont of NC. Since then erosion has washed away the land to the point where only the core of the once island volcano at Morrow Mtn NC is left. About 10 miles from there on Bus Rt 52 there is an outcrop of apparent basalt that has the shape of a cone In the way you'd expect from drawings of magma chambers that never made it to the surface.  What I can't seem to locate is the sutures where those two zones were.