One thousand years old passages – the dating of the Erdställe
There are regional differences. In Moravia, for example, Erdställe apparently were built only after the turn of the 12th to the 13th century.
No written sources are known that could tell about the purpose and date of the Erdställe. Therefore, we are dependent on archaeological and scientific dating. Here, the fundamental problem is to determine the time of construction, as objects found in the completed passages can only indicate the date of the period of utilisation, which could have been quite extensive.
View of the ancillary construction shaft Höcherlmühle during excavation. (Photo: Harald Schaller)The Erdstall Höcherlmühle (Teunz parish, Lkr. Schwandorf, Germany) was built between the middle of the 10th and the middle of the 11th century, according to the radiocarbon date of some charcoal found in the ancillary construction shaft. As these shafts only were dug and used during the digging of the corridors and chambers themselves and backfilled as soon as construction was complete, it can be surmised that the date in fact represents the period in which the Erdstall was built.
In the Erdstall in Rot am See (Lkr. Schwäbisch Hall, Baden-Württemberg, Germany), a passage had been retroactively turned into a narrow slip by fitting in blocks of stone set in clay mortar. The radiocarbon date of a sample taken from the clay grouting produced the result that this work very likely was carried out between AD 1034 and 1268.
A wooden board found in the undisturbed Erdstall of Niederpretz (Lkr. Passau, Germany) was dated with a high degree of probability to the period between AD 1045 and 1213.
Analyses of wooden fittings allow even more precise datings. Up to now, however, only few dendrochronological investigations are available. Three pieces of wood from the Erdstall Oberhofer in Gramastetten (Upper Austria) suggest that it was constructed between 1185 and 1239.
Objects found in the tunnel systems offer another way to a chronological classification. Often, however, these finds do not date from the period when the Erdstall was constructed, but from a later time, when it was used or backfilled.
Judging from pottery, most Erdställe were backfilled between the 15th and 18th centuries. Subterranean systems with similar characteristics – narrow, labyrinthine passages, chambers, and niches – exist from other eras as well. In Moravia, Bronze Age finds were recovered from the archaeologically documented structure in Modřice (district Brno Country, Czech Republic).
The radiocarbon method allows archaeologists to determine the age of finds of organic materials – such as plant remains or bone. It is based on the decay of a certain carbon isotope (14C), which forms in the upper layers of the atmosphere and is absorbed by all living organisms on earth via the food chain.
Cross section of a tree trunk. Each ring represents one year of its growth. By comparing the patterns formed by the annual rings of several trees, their age can be determined. Historical wood can be dated this way, too (dendrochronology). (Photo: StromBer, CC BY 3.0)