<p>There has been lots of works trying to reconstruct the evolution of the Gulf shoreline through time. They do not agree on the exact same dates (see this review by <a href="https://www.researchgate.net/publication/340066759_Sea_Level_Changes_in_the_Mesopotamian_Plain_and_Limits_of_the_Arabian_Gulf_A_Critical_Review" rel="nofollow noreferrer">Sissakian et al. 2020</a>), but they generally agree that there was first a transgression (sea level rise) episode following the last ice age, then a regression (sea level drop). Reasons invoked to explain the regression are (not mutually exclusive):</p>
<ul>
<li><strong>Change in climate</strong>. The sea level peaked around the post-glacial climatic optimum. After that, the climate got cooler, which means more ice at the poles and less water in the seas.</li>
<li><strong>Sediment filling</strong> of the Mesopotamian delta. The Euphrates and the Tigris carry a lot a sediments, which progressively accumulate in the lowlands, making the Gulf shoreline advance (seaward).</li>
<li><strong>Neotectonics</strong>. There are evidence for anticline growth under the area, which could have contributed to its rise above sea level. This activity also changed river paths, which could have promoted point 2.</li>
</ul>

CC BY-SA 4.0
2021-03-31T15:59:35.007Z
"shoreline retreat" I'm confused - did you mean "advance" ?
Keith McClary
CC BY-SA 4.0
2021-03-31T16:20:20.213Z
@KeithMcClary retreats from where it was from the ocean or beach's (or any set point on land's) perspective, advance from where it was from the land's perfective as a whole?
JeopardyTempest
CC BY-SA 4.0
2021-03-31T19:07:06.533Z
It seems to be defined terminology: [Shoreline retreat: Multi-annual average landward displacement of the high-water line.](http://www.coastalwiki.org/wiki/Shoreline_retreat)
Keith McClary
CC BY-SA 4.0
2021-03-31T19:55:11.207Z
Anyway, are you saying that sedimentation makes the shoreline move seaward?
Keith McClary
CC BY-SA 4.0
2021-04-01T07:10:09.030Z
@KeithMcClary Yes, I've edited the answer accordingly, thanks!
Jean-Marie Prival
CC BY-SA 4.0
2021-03-31T11:28:47.347Z
2021-04-01T07:09:14.593Z
2021-04-01T07:09:14.593Z
Jean-Marie Prival
<p>The Persian Gulf, today, looks like this.</p>
<p><a href="https://i.sstatic.net/IZQf6.png" rel="noreferrer"><img src="https://i.sstatic.net/IZQf6.png" alt="enter image description here" /></a></p>
<p>But about 4,000 years ago, it looked like this.</p>
<p><a href="https://i.sstatic.net/pb4rZ.png" rel="noreferrer"><img src="https://i.sstatic.net/pb4rZ.png" alt="enter image description here" /></a></p>
<p>This extended to the point where Ur, currently an inland city, was a coastal city. During this era, no other coastlines that I am aware of have had such a dramatic change. The research I've done has not yielded many results. I do believe that a while ago, I read something saying a flood of the Tigris and Euphrates rivers deposited sediment lower down. I was unable to find this again.</p>
<p>So my question is, what were the cause(s) of the change of coastline?</p>

<coastal>
Why did the Persian Gulf shrink during the influence of Ancient Mesopotamia?
Tateran
# Why did the Persian Gulf shrink during the influence of Ancient Mesopotamia?

(Asked by: username_0 on 2021-03-29)

The Persian Gulf, today, looks like this.

[![enter image description here](https://i.sstatic.net/IZQf6.png)](https://i.sstatic.net/IZQf6.png)

But about 4,000 years ago, it looked like this.

[![enter image description here](https://i.sstatic.net/pb4rZ.png)](https://i.sstatic.net/pb4rZ.png)

This extended to the point where Ur, currently an inland city, was a coastal city. During this era, no other coastlines that I am aware of have had such a dramatic change. The research I've done has not yielded many results. I do believe that a while ago, I read something saying a flood of the Tigris and Euphrates rivers deposited sediment lower down. I was unable to find this again.

So my question is, what were the cause(s) of the change of coastline?

**Tags:** coastal


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## 1 answers

### Answer by username_1 on 2021-03-31. Score: 5 | Accepted answer

There has been lots of works trying to reconstruct the evolution of the Gulf shoreline through time. They do not agree on the exact same dates (see this review by [Sissakian et al. 2020](https://www.researchgate.net/publication/340066759_Sea_Level_Changes_in_the_Mesopotamian_Plain_and_Limits_of_the_Arabian_Gulf_A_Critical_Review)), but they generally agree that there was first a transgression (sea level rise) episode following the last ice age, then a regression (sea level drop). Reasons invoked to explain the regression are (not mutually exclusive):

* **Change in climate**. The sea level peaked around the post-glacial climatic optimum. After that, the climate got cooler, which means more ice at the poles and less water in the seas.
* **Sediment filling** of the Mesopotamian delta. The Euphrates and the Tigris carry a lot a sediments, which progressively accumulate in the lowlands, making the Gulf shoreline advance (seaward).
* **Neotectonics**. There are evidence for anticline growth under the area, which could have contributed to its rise above sea level. This activity also changed river paths, which could have promoted point 2.

> **Comments:**
> **username_2**: "shoreline retreat" I'm confused - did you mean "advance" ?  
> **username_3**: @username_2 retreats from where it was from the ocean or beach's (or any set point on land's) perspective, advance from where it was from the land's perfective as a whole?  
> **username_2**: It seems to be defined terminology: [Shoreline retreat: Multi-annual average landward displacement of the high-water line.](http://www.coastalwiki.org/wiki/Shoreline_retreat)  
> **username_2**: Anyway, are you saying that sedimentation makes the shoreline move seaward?  
> **username_1**: @username_2 Yes, I've edited the answer accordingly, thanks!  

---

