In simple terms, a crannóg is an artificial island of variable size and height, roughly circular or oval in shape, constructed by piling earth and rocks on the bed of a lake or on a suitable mudbank or islet. While in some cases the surrounding waters could be waded through it was more usual for the semisubmerged mounds to be connected by a man-made causeway or footbridge to dry land or to make use of boats and canoes for access. Though some crannóga were permanently inhabited, others were occupied intermittently, sometimes laying abandoned for decades at a time. In general, these types of lake-dwellings seem to have been an almost uniquely Gaelic feature, that is Irish and Scottish, and were in use from the Late Bronze Age to the pre-industrial era, a span of some three thousand years. However the archaeological record has revealed that the most intensive centuries of construction were between 800 BCE and 200 CE for Scotland, and 400 CE to 1100 CE for Ireland. This late period coincided with significant cultural, social, political and technological changes in the latter nation though they do not adequately explain the broader motivation for building artificial lake-habitations or their enduring popularity.
In terms of the modern name, crannóg is derived from the Irish words crann “tree” and óg “young”. It is first encountered in the late 12th century, applied to the artificial island and to the structures on it, though it is not always clear which one is being referred to. However far earlier records describe the lake monuments as an inis or oileán, both translating as “island”. Occasionally these descriptions might be prefaced by the term “fortified” but by and large the Medieval Irish did not distinguish between natural and man-made isles, seeing them as broadly similar.
The location and construction of a crannóg
Most crannóga were situated on small lakes, usually one per location, though slightly bigger bodies of open water may have contained several artificial islands of lesser or greater sizes (in some cases these habitats would have clustered together; in others they were spaced well apart). Large lakes were avoided, probably to minimise the danger posed by strong waves and currents during storms which could easily damage or destroy the exposed platforms. More often than not the crannóg-builders looked to natural inlets or bays along the shore to provide some degree of shelter, the relatively shallow waters in these locations aiding construction or providing ready access to the artificial mounds when complete. If at all possible, existing features in the lake, surface shoals or banks, were used to anchor the crannóg, reducing the material and labour costs. In contrast only a comparatively small number of platforms were sited in deep water, sacrificing conveniance for the security that physical distance provided.
In many cases the islands were built in locations of some regional significance, where different territories butted up against each other or where previous, perhaps far older monuments such as burial mounds or cairns existed in the landscape. Navigable rivers and nearby water-crossings were also of importance, as was the control of fertile – and perhaps, prize – lands near the shoreline (which were invariably dedicated to pastoral rather than arable use). In these areas the contemporary importance of the location may well have decided for or against the presence of a crannóg, though the exact thinking of the builders and inhabitants can only be guessed at.
Whatever the initial incentive, the construction of a crannóg required some considerable community effort, probably during the summer when the waters of most lakes were calmer or lower. To begin with, a ring of closely set vertical wooden piles were driven into the lakebed, hammered as deep as possible into the mud to create the desired shape and size of the planned platform. The resultant space, surrounded by the tops of the thick poles poking out of the water, was then filled with alternate layers of peat, stone and brushwood until eventually a soggy mass rose above the surface. When sufficiently stable, in some cases through the addition of plank or flagstone revetments around the wave-lapped circumference, the top was finished with a compacted mixture of soil, sand and pebbles to provide a solid base and some degree of drainage.
This work would have involved considerable effort and hardship as men (and maybe women) laboured in water and mud for several days or weeks at a time, perhaps across the space of half a year or more. While some materials could have been floated to the location, others would have required multiple raft- or boat-trips from the shore, not to mention being brought to the lakefront in the first place by foot or cart. The construction work was no doubt dangerous too as the builders risked injury, illness or drowning in the difficult conditions.
It’s likely that some new islands may have required a second or third round of layering as they settled into the muddy lakebed, unexpected problems arising even after completion. Likewise, the first rains or storms would certainly have exposed any flaws in the building work, perhaps requiring further remedial labour. On a larger timescale natural or man-made wear and tear made some form of substantial refurbishment inevitable, additional construction layers raising the platforms up and outward. This mixture of permanence and impermanence gave crannóga a protean aspect which their inhabitants were well aware of.
In terms of access, while narrow bridges of timber planking or wattle may have existed, most islands seem to have relied on stone and turf causeways for entry. Some of these were partly submerged, possibly for reasons of concealment, requiring ankle or knee high wading. In a number of locations the paths followed circuitous routes across the water rather than leading directly from the shore, possibly to make visitors more visible to the island’s inhabitants or to create a grander impression upon arrival at the crannóg proper. The latter intention would certainly have been obvious in the case of the larger lake-platforms, quite a few of which were surrounded by timber and stone kerbing at the water’s edge, with high palisades – some possibly lime-washed – above. There is some evidence that these types of prestige crannóga were the seasonal or regular abodes of leading lords and kings, or of important religious figures in the Christian era.
The mounds piled furthest from the shore were true islands and could only be reached by boat or canoe. Unlike the crannóga near the lake’s edge, which were something of a compromise, the deep-water platforms clearly put status and security first. This is often reflected in their size, architecture and use. Evidence for small jetties and ports can be found on a number of these monuments, usually facing the nearest dry land (as with the causeways and bridges). In some cases while the rest of the platform may have been left open or with minimal protection the port or “harbour” would have featured an imposing entranceway of fencing and gates. In general, many mid-lake crannóga would have featured substantial revetments along the base, topped by fencing, protecting not just against intruders but also the elements. These were also the ones most likely to require regular maintenance and were at greater risk of abandonment.
The role of the crannóga
The purpose of each individual crannóg varied greatly in time and place. Some undoubtedly functioned as off-shore pens for small livestock, probably pigs, goats and sheep, the location providing some safety from predators, be they human or animal. In such cases a simple wattle fence or timber palisade, a metre or more high, around the edge of the raised platform would have kept the animals inside (though some places might have forgone even that much). Interior fencing would have created open pens while some shelter could have been provided through small barns or lean-to huts. However, this was likely temporary rather than permanent, intended for overnight stays or during periods of inclement weather, disease or passing danger from raiders or wolves. Longer use for animals would have been problematic, predicated on the size of the island, ease of access and other local factors. Conditions on a crannóg, despite attempts at drainage and the creation of a floor of sand and pebbles, possibly strewn with reeds or straw, were invariably damp, and animal waste would have added considerably to the poor footing underneath. Maintaining the well-being of confined livestock would have required regular trips by causeway or boat for feeding and watering, or to remove excess effluent. Of course, this routine would have been made easier if the herders were housed with their charges.
Close confinement between different sexes or species might also have caused problems. During mating season some animals needed separate pens for males and females unless confined there for breeding purposes, while domestic pigs were almost as hostile as their wild boar cousins. Cattle would have been especially difficult to bring to and from a crannóg unless a weight-bearing causeway was present or the island was in shallow, fordable waters (in which case some sort of long slipway would have been required from the raised platform down to the lakebed). Though we cannot be certain, practical evidence makes it unlikely that the islands, regardless of size, housed cows or bulls for any great period of time, at least before the war-ridden 15th century.
Other crannóga undoubtedly functioned as mainly human habitats, for extended families of farmers or their aristocratic overlords. A few of the larger lake dwellings supported substantial free-standing structures, from timber walls to well-made houses, indicating long-term use. However this does not guarantee that these locations were occupied at all times throughout the year, or even from year to year. Some may have been associated with seasonal accommodation, suitable during the summer months when the crannóga may have been less prone to damp (while the winter would have seen them left to the cold and the gales). Or they may have served as one of several widely spaced palaces used by important regional kings during frequent progressions around their subject territories.
In some cases the sustained use of a crannóg can be deduced not from its structural remains but from the waste that the inhabitants created during their own lives. This is especially true of so-called middens, prehistoric rubbish tips, which lake-dwellers inadvertently created by simply dumping their refuse into the water on one side of their island homes. These mounds yield a wealth of analytical materials, and simply put, the greater the amount of refuse the greater the length of human occupation. In a similar vein, dedicated cesspits, Medieval toilets, are also found on crannóga, some dug down from the raised platform into the watery subsoil beneath. A purpose-made space for human waste implies a prolonged need and some cesspits show clear signs of maintenance or refurbishment. Both of these features raise questions about health and sanitation in the damp and possibly mouldy conditions of lake-dwellings.
There is no doubt then that only the wealthy or powerful were likely to have invested in the maintenance of large and well-equipped crannóga, a time-consuming effort that could only be justified by some perceived advantage gained over life on dry land. In the case of those crannóga displaying simpler habitations it can be assumed that they belonged to the ordinary people or were for occasional use and so required nothing of any lasting value. Not unrelated to this was the fact that some lake dwellings seem to have served as secure centres of industry, mainly agrarian or technological in nature, with evidence of quern-stones (for the grinding of grain) and metal-working. Whatever the case, the early buildings on the islets conformed to the same styles used in non-maritime settlements, invariably the well-known Irish or Celtic roundhouse and its derivatives. It was only later, around 800 CE, that oblong houses began to creep in, as with ordinary homesteads, influenced by the mainstream European architecture of the Scandinavian-Irish towns and Christian monasteries.
Related to the latter, a small number of crannóga, especially those predating Christianity, may have been constructed for ritual or ceremonial functions or may have been adapted for those uses. These include assemblies associated with royal coronations, communal festivals or even treaty negotiations. It’s likely that the popularity and continued use of certain lake dwellings may have been linked to local folk-memories and traditions largely lost to us. By the Medieval period a number of saints – and their immediate followers – were living in seclusion on several natural or artificial islands. Meanwhile a few wealthy monasteries were undoubtedly using the lake dwellings in much the same manner as secular communities: as permanent or temporary abodes, places of refuge or storage, pens for livestock, gathering and meeting points, shelters for hunters and fishermen, or places of worship and ceremony.
The legacy of the crannóg in the Irish landscape
The last hurrah of the crannóga took place from the 15th to 17th centuries as the islands and their offshoots provided the native Irish with moated residences, fortresses, treasuries, depots for weapons, prisons and hospitals. The more isolated, the greater the advantage, as the country groaned under the weight of English invaders and colonists. In some cases, artificial islands abandoned centuries beforehand were restored and expanded, the age of musket and cannonball requiring the addition of defensive walls of turf and stone in some places. The last recorded evidence of the crannóga in active use comes from the 18th and 19th centuries, when poor vagrants or armed opponents of British rule hid on their bleak, usually overgrown surfaces. Though some 1,500 artificial islands have been identified by historians and archaeologists, mainly in the midlands, northwest, west, and north of the country, many more remain to be discovered. Very few indeed have been subject to a thorough or modern investigation by professional researchers. As much as we know about the long history of the crannóg in Ireland, and Scotland, there is much more to learn.
Filed under: Archaeology, Architecture, History, Irish Mythology - Seanchas, The Irish Language - An Ghaeilge Tagged: Artificial Island, Celtic Ireland, Crannóg, Crannóga, Inis, Lake Dwelling, Medieval Ireland, Middle Ages, Oileán