Benbulbin, is a large rock formation in County Sligo, Ireland. It is part of the Dartry Mountains, in an area sometimes called “Yeats Country”. The mountain was shaped during the ice age, when Ireland was under glaciers. Originally it was a large plateau. Glaciers moving from the northeast to southwest shaped it into its present distinct formation.
Benbulbin, and the Dartry Mountains as a whole, are composed of limestones on top of mudstones. These rocks formed in the area approximately 320 million years ago in a shallow sea. Uppermost in the limestone layer is a thicker, harder limestone called the Dartry Limestone Formation. Below this is a thinner transitional limestone formation – the Glencar Limestone Formation. Further down, the lower slopes consist of shaly mudstone known as the Benbulben Shale Formation. Scree deposits are found near the base.