The Ring of Gullion

The Ring of Gullion is a Volcanic Ring Dyke formed by the collapse of a volcanic caldera and is widely considered to be the best example of this volcanic feature in the British Isles.

The Ring of Gullion is the remnants of a volcanic caldera which must have been massive as the ring has a diameter of 11km (7 miles) and covers more than 15,000 hectares (37,000 acres).

The volcanic activity which led to the formation of the ring occurred during the Palaeogene era (66 million to 56 million years ago) and was linked to formation of the North Atlantic. This activity was responsible, in Ireland, for the creation of the Giant’s Causeway in County Antrim and the upwelling of magna across the Mountains of Mourne.

Simultaneously magna which intruded into the centre of the volcano was the origin of Sileve Gullion which at 570m/1,890ft) is the highest peak in County Armagh.

The current geology of this part of County Antrim was however made more complicated by later glacial activity which eroded the region’s weaker sediments and left the more resilient volcanic rocks standing proud as Ring of Gullion and Slieve Gullion

Cam Lough which is now a reservoir inside the ring was a glacial ribbon lake which formed in a geological fault running through the low ground between the ring and the lower northern slopes of Slieve Gullion.

Source: ‘Ireland’s Forgotten Past: A History of the Overlooked & Disremembered’ by Turtle Bunbury (ISBN: 978-0-500-02253-5)