Hunting the drowned “Red Snake” – The Sasanian Persian Empire’s Great Walls
One more field site for the year - at least I think so! A couple of years ago Prof. Eberhard Sauer (Edinburgh University) got in touch as he has had a 10yr project investigating the “Red Snake” of Persia. This is better known as the Gorgan Wall that once ran near the border of Iran and Turkmenistan from the Caspian Sea in the west and the Elburz Mountains in the east.
At a known length of over 195km it was pretty significant as
an ancient line of defense. However, not
so today as the westernmost part not visible even to archaeologist in the present landscape. The problem with the wall is that it was constructed of mud
bricks and so the ravages of time and the deconstruction (robbing) of bricks
for use means that it is often difficult to see today. However there is a silver lining, or at least
a geophysical signature silver lining, that results from the use of
bricks. That is that the firing process of
making bricks can give a strong magnetic signature to the bricks. To make them requires a few key ingredients,
namely a good clay with some larger silt or sand grains and water. Lucking the clay is in abundance all along
the wall’s path but water in this semi-arid area can be a problem. So a solution was found by diverting local
rivers to run feeder canals to a ditch that ran along the length of the wall
thus providing not only the vital water but at the same time a quarry for the
clay and when the wall was completed an extra defense line!
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| C5-6th Kiln |
195km of wall requires quite a few bricks – it has been
estimated that over 200 million in total were used! Making these bricks was achieved using
temporary field kilns set up all along the path of the wall at approximately
50m intervals. The wall was garrisoned
by an arm of over 20,000 soldiers barracked in at least 30 forts. The project team have spent the last few years excavating some of these kilns together with
some of the forts and sections of the wall itself. They have also investigated a sister wall,
the Tammisheh Wall that ran from the southeast corner of the Caspian south to
the Elburz Mountains. Through C14 and
OSL (Optically Simulated Luminesance) dating their work puts a construction
date on both walls to the Sasanian Persian Empire between the 5th
and 6th Century AD.
So what am I doing here?
The western extent of both walls is unknown. Historical writing describes how the walls
enter the Caspian Sea and certainly the Tammisheh Wall can be traced almost to
the modern shoreline but where it goes after that is unknown. Some descriptions even suggest that both
walls were joined up. So we are back again to our old problem of changing sea
levels and with it the usual battering that this can give to the landscape and
our human endeavours.
So I am here to help out with the searching for the walls,
both on the sea floor and beneath it if they have been covered by more recent
sediments. We were looking for
upstanding bricks or a scattering of bricks on the seafloor with the hope they
would not have disintegrated. Beneath
the seafloor the hope was again to find lines of bricks or mounds. Perhaps we would also see the cross –section
of the trench that ran along the wall.
With the magnetic signature associated with the kilns on land this might
stand out too but for this first preliminary survey I chose to use the Tritech Seaking
Parametric Sub-bottom Sonar that we have found so effective in the shallow
waters of Orkney together with an ultrahigh resolution Tritech Starfish 990kHz
Sidescan Sonar. A great advantage of both these systems is that they can be
taken as hand luggage on flights!
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| small boat work with Tritech Sub-bottom sonar and Starfish Sidescan |
We started with the Tammisheh Wall as the projection into
the Caspian is better known. The parametric sonar proved worthwhile once again
despite the occasional gas blanking by picking out a strong reflection from the
brick scatter on the sea floor. The
signature of this continued as it became buried further offshore with up to 2m
of sediment. After approximately 3km it
abruptly disappeared or terminated. The
scatter on the sea floor was also mapped with the sidescan sonars from which the
surface brick scatter was readily identified together with a number of linear
features.
Given the time available for this trip and the relatively
less knowledge on where the Gorgan Wall might be crossing the shore line we had
a much larger potential target area to cover.
With a few days of poor weather (yes the Caspian does get rough with
over a 1m wave and swell heights) we covered a large area but without finding
any definitive wall signatures. So more
and better targeted data acquisition is needed for the marine side here. What I now propose is to return and try with
a magnetometer and an electromagnetic ground conductivity meter to survey from
the last known western point of the wall across the land and shallow lagoons to
the shore. If we can trace this then we
stand a much better chance of mapping it offshore, if that is where it goes. Video summary of the trip:
I had a fantastic crew out with me on the water (I cannot
thank Hamid, Bardia and Hassan enough) and also back in the base as the joint project leaders, Dr Jebrael Nokandeh of the National Museum
of Iran and Eberhard have assembled a talented team of archaeologists for the project.
So, another privileged trip to work with some great people,
such friendly banter, engaging conversation, fantastic archaeological
potential, some great food and wonderful scenery – the bird life on the Caspian
is stunning! I can’t wait to return next
summer equipped with magnetometers and electromagnetic gear to continue the
hunt.
Iran-British Gorgan Wall Project Team
Dr Jebrael Nokandeh (National Museum of Iran);
Mr Hamid Omrani Rekavandi (Iranian Cultural Heritage, Handcraft and Tourism
Organisation of Golestan Province); Bardia Shabani, Hassan Taji, Mohammad
Ershadi, Maryam Hosseinzadeh, Mohadeseh Mansouri, Meghdad Mirmousavi, Mohammad
Bagher Bayati Mehdi Jahed, Alireza Salari, Esmaeil Safari Tamak, Majid Mahmudi,
