Birka’s harbour in an international comparison
After two and half weeks of excavation, this year’s campaign comes closer to its end. Only a couple of days are left for the international team, to proceed which the research. But one of the main goals, to find more timbers that can most likely be related to a former harbour construction has in some cases already been achieved (check out blogpost 23/8 to get hold of some more detailed information of some of these years’ timber findings and the ones from earlier years). This gives us now the opportunity to think about how Birka’s harbour might have looked like, by taking constructions, known from excavations that have been taken place at several places in northern Europe, into account. At the same time these comparisons enable us to set the results into the broader context of the development of harbours during the Viking age as well as those from early and high medieval times.
Among the excavated timbers, especially one log sticks out. At this log, one of its ends has been worked to a peg.
In this case the peg forms a fishtail so the log can be called a “laxstjärtstimmer”. Logs with different types of pegs have been found at several sites, but their interpretation differs. One of the most common interpretations is that they served as poles in a yoke construction. A yoke needs at least of two poles, which form, together with a third timber, a stable construction. One way to connect the poles was to carve their upper ends to a peg and putting the third timber with holes at the ends above them. Such constructions have been used for bridges in inland waters, as well as for harbour related facilities like docks and jetties. These kinds of bridges are known from Viking age Scandinavia, but also from the southern Baltic, where Slavonic tribes settled.
Another interpretation that might fit the fishtail peg, is, that this end has been used to drive the other end of the log into the sea ground. To manage that a rope has been attached to the peg and with the help of a large three pole, the log could be lifted upwards in order to ram it deeper into the ground. When the log was into position, the peg has been cut off. If this interpretation, which was made up for the bridge of Ravning enge in Denmark, would fit, it would mean that this log has never been part of any construction, because the peg is still at its place.
A third interpretation that could be likely is that the log has served as a pole, to tie ships to it. Such poles are called “Dykdalb”, and could stand by itself or be part of a more stable construction. This interpretation would also explain the fishtail peg that prevents ropes from slipping of. A rope found close to the log may support this interpretation.
For instance “Dykdalb”, without pegs, but with ropes still attached to it are known from the Viking age settlement of Hedeby and the late 11th/early 12th century harbour area of Schleswig.
To sum up the mentioned examples, it seems likely that the “laxstjärtstimret” found in the Birka harbour was part of a harbour facility. Probably a yoke based construction, like a dock or standing alone and serving as a “Dykdalb”.
Several other logs that showed up during the excavations, doesn’t have such clear construction features. Mainly because their ends have been rotten, burned or the logs have been part of a different type of construction. Together with the stone assemblies the logs might have belonged to a jetty. One may think of a wooden, probably log cabin like construction filled with stones. Such kinds of jetties are well known from different places from Viking age and medieval Norway. They enabled ships to moor alongside in order to be easier loaded or unloaded.
So now we can see that the current excavation has been (and is still) able to gain more information about the facilities in the Viking age harbour of Birka, while several parallels from different places in northern Europe enlighten the dense networks that existed during the Viking age.
Blogg by Felix Rösch
Photos: Maija Huttunen/Pintafilmi Oy