Ben Bulben

Binn Ghulbain

County Sligo is home to the iconic Ben Bulben, a striking mountain in the heart of Yeats’ County. Standing at over 500 meters tall, it can be seen from almost all corners of the county on a clear, sunny day, which can be a rarity in Ireland.

Although I never came across myths on the origin of this landscape, the mountain itself has great literary and mythological significance which is worth mentioning. It was a favorite subject of William Butler Yeats and an important location in the Diarmuid and Gráinne saga.

The view of Ben Bulben, looking north-east, from atop Knocknarea on a clear July day.

The Legend

The Pursuit of Diarmuid and Gráinne is a 17th century celtic folktale that tells the story of Grainne, the daughter of an Irish war lord who was betrothed to the giant Fionn MacCool, the leader of the warrior band the Fianna, and her elopement with Diarmuid, a young Fianna warrior.

The saga begins at an enormous wedding feast, a celebration of Grainne and Fionn’s engagement. During the feast, Grainne lays eyes on Diarmuid, the young, handsome Fianna warrior, and falls in love at first sight. The love she feels is so powerful that she decides to run away from her wedding to Fionn to elope with Diarmuid. With this plan, she dispenses a magical potion and puts the rest of the guests to sleep. She asks Diarmuid to elope with her but his loyalty is to Fionn and the Fianna. But Grainne is determined; she puts a fateful spell on Diarmuid that causes him to fall in love with her, forever.

The lover’s runaway with Fionn in hot pursuit, taking advantage of all the different nooks and crannies Ireland’s landscape has to offer (it’s impossible to travel across Ireland without coming across a spot or two where Grainne and Diarmuid are fabled to have laid or hid). They manage to evade Fionn for years and over time his rage subsides. A half-hearted reconciliation takes place and Fionn allows the couple to live in peace.

But one day, while wandering through Sligo’s wilderness near Ben Bulben, Grainne and Diarmuid come across Fionn who invites Diarmuid to a wild boar hunt. It was prophesized that Diarmuid would someday be killed by a wild boar, but despite the ill-fated prediction, he accepts the invitation. Diarmuid and the boar engage in an epic battle at Ben Bulben and Diarmuid emerges the victor, killing the boar after sustaining a fatal wound.

The only person that could cure the dying Diarmuid is Fionn. A drink of water, cupped from the hands of the giant, would have magically restored the warrior back to health. Despite the pleas of Grainne and members of the Fianna, Fionn refused to help Diarmuid out of jealously and resentment. The pleas continued but by the time Fionn changed his mind, it was already too late. Grainne had lost her young Fianna warrior. Diarmuid lay dead on Ben Bulben.

A cave in the side of the Dartry Mountains, fabled to be the last bed of Diarmuid and Grainne.

Further along the Dartry Mountains, if you take the wonderfully scenic Horseshoe Drive, you will come across a spectacular site of Irish mythology – a large cave where it is said that Diarmuid and Grainne spent their last night.

The Geology

Ben Bulben is comprised of only three different lithological formations: the Benbulben Shale Formation, the Glencar Limestone Formation, and the Dartry Limestone Formation. They were all formed between 359-318 million years ago, during the Mississippian Epoch, a member of the Carboniferous period, a unit on the geologic time scale. As you shall see, the dramatic cliffs and slopes, the likes of which have inspired William Butler Yeats and others, are the result of a simple geologic phenomenon.

The Benbulben Shale Formation is the oldest of the four units and lies at the base of the mountain. As you might imagine, this formation contains predominately shale beds. These black shale beds are thinly bedded and fossiliferous, containing brachiopods, corals, bryozoa, and caniniids –signs of a productive, ancient marine environment. The formation is about 90 meters thick which correlates to the large, sloping base of the mountain.

The Benbulben Shale Formation gradually transitions into the Glencar Limestone Formation. Unlike the previous, this formation is made up of both limestone and shale.  The limestone beds are only 10-20 centimeters thick and contain evidence of ancient organisms burrowing through the sediments (bioturbation.)

The last unit that can be found on Ben Bulben is the Dartry Formation. It is the youngest unit and lies on top of the Benbulben Shale Formation and Glencar Limestone Formation. It is made up of two types of rock: a blue/gray limestone with chert nodules and fossils, and a mudbank limestone.

During the early Carbonifierous, about 359 million years ago, County Sligo was positioned at about 10˚ latitude. At this time, the climate was much warmer than today and sea level was on the rise, submerging Ireland under a shallow, warm tropical sea. This time experienced a period of transgression. Transgression is a geologic term that describes a rise in sea level relative to the land. When the sea is rising relative to the land, the shoreline moves landward creating deeper seas at a given point. In the case of Ben Bulben, the Benbulben Shale Formation the depositional processes of a river delta near the shoreline. As the seas continued to rise, and Sligo was submerged under warm, shallow, tropical seas, the Glencar Limestone formation was formed. The presence of marine fossils tells us that the waters were shallow and calm enough for biological activity. The blue/gray limestones of the Darty Fortmation at the top of the mountain lack fossils, a depositional setting interpreted as a deep marine environment.

During the Last Glacial Maximum, 26,000 million years ago – 19,000 million years ago, Ireland was covered in glaciers. As the glaciers flowed, they carved out the distinctive landscape we see today. The reason Ben Bulben looks the way it does, with steep cliffs capping gently sloping land underneath, is because of the different formations and rock types. Limestone is much more resistant to weathering and erosion than shale. During glaciation it resisted the erosional forces of the flowing ice and formed steep cliffs and a hard, flat “cap”. The shale layers underneath are soft and easily weathered. Over time ice, wind, and rain shaped the shale layers into Ben Bulben’s gentle slopes.

The Poem

Under Ben Bulben – William Butler Yeats, 1939


Under bare Ben Bulben’s head

In Drumcliff churchyard Yeats is laid.

An ancestor was rector there

Long years ago, a church stands near,

By the road an ancient cross.

No marble, no conventional phrase;

On limestone quarried near the spot

By his command these words are cut:

Cast a cold eye
On life, on death.
Horseman, pass by!

W.B. Yeats’ grave in Drumcliff churchyard.


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