[PetitSasquatch]

I'm having trouble understanding how this could be so.

If sedimentation gradually pushed the sea away from Ur, how could the sea level now also be higher?

Wouldn't this imply that today one would be driving up hill from Ur to sea's coast?

Genuinely, curious to know how this whole process works.

[AlotOfReading]

Treating sea level as a global constant for practical purposes, this is what the graph looks like of recent sea level compared to modern times [1]. As you can see, sea level has largely risen since the last glacial maximum.

But thousands of years ago, the dirt that makes up southern Iraq simply wasn't there yet. Since there wasn't any dirt "displacing" the Persian gulf, it extended far inland from the present extent [2]. Over the intervening years, the Tigris and Euphrates transported all of that eroded sediment down from the highlands of Turkey and Iran, pushing the gulf out and forming a vast river delta where it used to be. That river delta has in turn dried up and shriveled in various ways over time, as the region became more arid and complicated hydrological things I'm not remotely qualified to talk about happened.

To put it another way, you can think of the gulf as a vast valley, with cities like Ur dotted along the ridgelines of the valley. What's happened is that the alluvial deposition from the rivers has simply filled in the bottom of the "valley".

This is actually how mesopotamia as a whole was formed geologically. The actual rock of the continental shelf is being squeezed between the Arabian and Eurasian plates and it buckled downwards in Iraq, forming a huge, flattish valley called a foreland basin. Erosion from the tectonic margins filled it in over time.

[1] https://upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Po...

[2] https://upload.wikimedia.org/wikipedia/commons/e/ed/N-Mesopo...

[PetitSasquatch]

Thanks, that makes much more sense now. Appreciated.