For centuries, the tale has been passed from generation to generation: how the Irish giant Finn McCool built the Giant’s Causeway to fight his Scottish rival, Benandonner, by hurling chunks of the Antrim coastline into the sea. Now, scientists have revealed it was intense volcanic activity during a “major globally impacting volcanic event” – and not a legendary battle – that led to the formation of the coastline’s 40,000 distinctive interlocking basalt columns about 60 million years ago.
The Giant’s Causeway is a Unesco world heritage site on the coast of County Antrim in Northern Ireland, known for its hexagonal basalt columns that appear to form a natural staircase from the cliff foot and disappear under the sea. Geochronologists from the British Geological Survey (BGS) and the Geological Survey of Northern Ireland (GSNI) have determined that the volcanic activity responsible for the Causeway occurred over a period of 5.5 million years – eight million years less than previously estimated. The new research also definitively connects the first lava flows on the Northern Irish plateau to the same volcanic activity that formed the giant basalt columns in Fingal’s Cave on the Scottish Hebridean island of Staffa, rocks that were previously thought to have formed millions of years after the Causeway.
“New research reveals the Giant's Causeway formed in just 5.5 million years, linking it to a global volcanic event.”
For decades, the timeline of the Giant’s Causeway’s creation was poorly understood. The previous estimate of formation over about 13 million years was based on less precise dating methods. The new study used high-resolution geochronology to piece together volcanic rocks across the North Atlantic, focusing on Northern Ireland. This has not only revised the timescale but also linked the Causeway to a globally significant volcanic event recorded in rocks as far away as Greenland. The same volcanic activity is also connected to rock formations on the nearby Mourne mountain range, on the Hebridean isle of Rùm, and to magmatic activity on Skye, placing the Causeway within a broader, precise global geological context for the first time.
For UK readers, the Giant’s Causeway is one of the greatest natural wonders of the UK and a major tourist attraction. This research deepens understanding of how iconic landscapes are formed, and it highlights the dynamic geological history shared between Northern Ireland and Scotland. The discovery that volcanic activity happened more rapidly than thought may also influence future studies of similar volcanic formations elsewhere in Britain, such as those in the Inner Hebrides. Additionally, the ability to link events across the North Atlantic provides a clearer picture of large-scale volcanic episodes that may have affected global climate millions of years ago.
Q: How were the basalt columns of the Giant’s Causeway formed? The columns formed when intense volcanic activity forced molten rock up through cracks in the earth. Thick lava flows then cooled, contracted and cracked, creating about 40,000 interlocking basalt columns.
Q: How old is the Giant’s Causeway? Scientists now believe the volcanic activity that formed the Causeway occurred about 60 million years ago, over a period of 5.5 million years – eight million years less than previously thought.
Q: Is the Giant’s Causeway connected to similar formations in Scotland? Yes. The research definitively links the Causeway to the basalt columns of Fingal’s Cave on Staffa, as well as to volcanic rocks on Mull, Rùm, and Skye, showing they were all part of the same major volcanic event.
What happens next? The research is part of a wider initiative at the British Geological Survey to reconstruct volcanic timelines across the North Atlantic. Further studies may examine the environmental impacts of this volcanic event, including its potential role in ancient climate change. The revised timeline also opens questions about other volcanic formations in the UK and Ireland that may now require reassessment.