Geology, Belcarra in Co. Mayo


The Belcarra area is notable for its Drumlin typography. Belcarra village itself nests cosily at the foot of a steep drumlin.

The water reservoir for the area is built atop Fairhill the highest drumlin in the area. Ancient ringforts crown many of our local drumlins.


Drumlins are long ridges of boulder clay created by the movement of the ice at the end of the last ice-age about 10,000 years ago.

In the Belcarra area all the drumlins have a North-South orientation (no compasses needed here!). Nowadays they present as long green hills about 100 ft above the surrounding countryside. The southern slopes of the drumlins are often quite steep, whilst the northern slopes are invariably gentler.

The word 'drumlin' itself derives from the Irish language. The word 'droim' in Irish means 'back' - as in 'pig's back' - and the hills were regarded as resembling pigs' backs as they lined up parallel to one another.

Flora and Fauna

After the ice-age the wet areas trapped between the drumlins produced weeds and mosses and other wetland plants in abundance and over the years as these plants decayed they produced our bogs and peatlands.

North and south of Doonamona Castle you can view a Doonamona marsh which is still vigorously growing. At Cloonconragh, west of Belcarra is a very extensive cutaway bog with a delightful variety of wetland flora and fauna.


The base rock in the area is limestone and many of the field bounderies are built of limestone. This fossil-rich stone was laid down at the bottom of a tropical sea millions of years ago.

The stratification of the rock can be observed south of the bridge at Belcarra or at Bridgemount on the Ballinafad road. The rock abounds in sea shells and corals of the period.

At the entrance to "Tobar a' Bhaile" near Roslahan, on the Manulla road, you can see arrangements of coral set in Lower Carboniferous Limestone.