Month: April 2014

Slievemore; geology and ecology

The first post on this blog briefly described the range of archaeological sites that are located on and around Slievemore Mountain on Achill Island. Having set the archaeological scene it seems like a good time to take a brief look at the geology and ecology of Slievemore.

An unusual view of Slievemore from the remote northern side of Achill Island

An unusual view of Slievemore from the remote northern side of Achill Island

Slievemore is one of a series of notable mountains that form a very important part of the landscape of the west and north west coastal region of County Mayo, a group that includes the well-known pilgrimage Mountain of Croagh Patrick near Westport, Knockmore on Clare Island, and Nephin Beg near Ballycroy. This part of County Mayo is a mixture of low lying coastal plains, inland bogs and rolling hills separated by large steep-sided and highly visible mountains. As you move around the area these distinctive summits form a familiar backdrop, recognisable landmarks that allow you to identify your relative position on the ground. Whilst the low lying plains and bogs can be a little lacking in distinguishing features, each of these prominent hills has a very particular character making them instantly recognisable whenever they come into view.


Looking towards Clare Island from Achill

Slievemore is the second highest mountain on Achill at 671m OD and dominates the western half of the island. The mountain is very much a discrete entity, with low valleys at the east and west separating it from the adjacent lower ridges, whilst on the northern side it plunges steeply down into the Atlantic Ocean. To the south there is a low-lying bog that stretches out to the coast at Keel and which contains the large fresh water lake, Keel Lake. Slievemore has reasonably gentle lower slopes stretching up to around the 250m contours. Above this height the ground become considerably steeper and is dominated by large scree slopes. At the north east, just behind the village of Dugort there is a substantial glacial corrie that provides a view that is stunningly beautiful and frankly rather intimidating. Along the northern side of the mountain there are low but steep cliffs that drop into the Atlantic and numerous deep inlets that have been cut into the mountain by strong wave action. Above the scree slopes there is a wide ridge that slopes up from the west towards the summit. The ridge is covered by exposed boulders, broken up and eroded peat formations and shallow pools of crystal clear water. As the summit is approached the ridge becomes increasingly narrow and the summit area itself is very small and flanked by very steep drops to the north and south. Views from the summit are quite magnificent, with huge areas of Mayo visible to the north, east and south and the expanse of the Atlantic Ocean visible to the west beyond Croaghaun Mountain and Achill Head. A small circular cairn and a trigonometry point mark the summit.

One of the deep inlets cut into the northern side of Slievemore

One of the deep inlets cut into the northern side of Slievemore

The geology of the mountain comprises quartzite and schist that descend towards the lower contours close to the Deserted Village. There are frequent veins of milky white quartz running through the mountain and a massive quartz boulder, known, as ‘The Star’ lies high up on the southern side where it is very visible landmark on most days of the year. Overlying the bedrock is a deep layer of grainy sandy till that contains frequent small boulders and pieces of the white milky quartz. Today the till is covered by an expanse of Atlantic Blanket Bog, the depth of which varies considerably from one location to another. This peat bed consists of the partially decayed remains of bog plants such as sphagnum moss, ling heather and purple moor grass. Waterlogging and the acidic ground conditions halt the normal process of bacterial decay and the partially decayed plant remains form deep accumulations of dark brown and black peat. Despite the steepness of the ground Slievemore provides an extensive area of grazing today for reasonably low numbers of sheep, but in the past it is likely that far larger flocks of sheep have been grazed on the mountain, alongside cattle and goats.

At several of the excavation sites examined by Achill Archaeological Field School a pre-peat soil has been revealed directly overlying the till and underlying the peat bed. This pre-peat soil, grey sandy silt, demonstrates that prior to the onset of bog growth the mountain would have been covered in lush pasture. In the centre of Slievemore Roundhouse 1 a post abandonment soil was discovered that had become waterlogged preserving thousands upon thousands of individual blades of grass, a discovery that was particularly evocative of this earlier environment.

The steady accumulation of peat on the mountain has provided ideal conditions for the preservation of the remains of stone buildings, which are enveloped by protective layers of peat following their abandonment. The Middle Bronze Age roundhouses that were excavated on Slievemore between 2006 and 2009 are among the best-preserved and most intact structures of that period known from Ireland. The Early Medieval Kiln complex excavated between 2010 and 2011 was an equally impressive discovery and to date no clear parallels for such a substantial set of industrial buildings from this early period have been identified to date. No doubt future work on Slievemore by Achill Archaeological Field School will continue to reveal more examples of these hidden architectural gems.

Whilst the archaeology of Slievemore has been the focus of the majority of the work of Achill Archaeological Field School there are a number of other locations where the field school has undertaken important research. The next post on this blog will take a look at one of the areas of the island that is a perennial favourite with the students; Keem Bay, Croaghaun Mountain and Achill Head.

Achill Archaeological Field School runs a variety of archaeological courses that are suitable for archaeology and anthropology students, professional archaeologists and inquisitive members of the public. Visit our website at for details of all of our courses and information about the many exciting projects we have undertaken. Residential and non-residential options are available throughout the summer. We also specialise in Guided archaeological tours of Achill and the Corraun Peninsula.



View of Slievemore and Croaghaun from the Minaun Cliffs at Keel





Welcome to our Blog!

The entrance of Roundhouse 2

Students excavating the entrance of a Middle Bronze Age Roundhouse in 2010.


Hello and welcome to our new Blog!

We’re going to use this new blog to tell people about some of the different archaeological sites that can be found on Achill Island and in the surrounding areas of County Mayo. We’ll also be using it to share some of the results of the excavations we are undertaking on Achill, including the ‘Cromlech Tumulus’ on Slievemore and the mysterious ‘Pony Graveyard’ recently discovered on the beach at Dooagh. So watch this space!

The staff at Achill Archaeological Field School are heavily involved in the Irish Archaeological Community and we’ll certainly be using this blog to share information about the work of our friends and colleagues, and other interesting things that we might come across from time to time.

I think a very good place to start, seeing as it is so central to so much of the work of Achill Archaeological Field School, is the mighty mountain of Slievemore. This behemoth dominates the western half of the island, with its dramatic profile and lofty summit. Referring to archaeological landscapes as palimpsests may be a tad clichéd but in this case it really is perfectly appropriate.

The earliest archaeological remains on Slievemore are a series of Megalithic tombs dating from the Neolithic period and probably constructed around 3500BC! Today two Court Tombs and a Portal Tomb are clearly visible and several other megalithic sites are present, even if it’s not exactly clear what types of site they represent… yet!

During the Bronze Age Slievemore was a farmed landscape and there are numerous large houses, two of which have been partially excavated and found to date to between 1400 and 1200BC. The houses are constructed within an expansive field system which has been surveyed in detail and subject to small scale excavation.

As with most of Ireland the Iron Age remains elusive, but we are slowly beginning to put together a complex picture of Medieval Slievemore. Traces of settlement sites, ecclesiastical sites and industrial sites have all been identified but much more work needs to be done on this period before we can properly understand the scope of activity taking place on Slievemore during the period.

Superimposed on these early landscapes is a very dense and well developed post Medieval farming landscape. The famous Deserted Village runs along one of the lower contours of the mountain and is accompanied by a complex arrangement of roads, pathways, garden plots and fields. Military activity at the start of the Nineteenth Century is evident in the remains of a Napoleonic Era Signal Tower on the adjacent ridge. Between the signal tower and the end of the Deserted village there is a quartz quarry that was once connected by a tramway to the quay at Gubalennaun Beg on the coast beyond Pollagh.

But I think before we get to carried away with all of this we ought to have a look at the physical aspects of Slievemore that underpin the various archaeological landscapes. The geology and environment of Slievemore seem like a very good topic for our second post!


List of archaeology courses for 2014

Slievemore Mountain

Slievemore, with the small artificial island or Crannóg at Loughannascaddy in the foreground.