For centuries, the story went that the Irish giant Finn McCool built the Giant's Causeway by hurling chunks of the Antrim coastline into the sea to fight his Scottish rival, Benandonner. Now scientists have revealed the truth: intense volcanic activity during a “major globally impacting volcanic event” created the 40,000 interlocking basalt columns about 60 million years ago — and in a far shorter time than previously thought.
Geochronologists from the British Geological Survey (BGS) and the Geological Survey of Northern Ireland (GSNI) have discovered that the volcanic processes that formed the Causeway took place over just 5.5 million years — a staggering eight million years less than earlier estimates. The research, published after years of fieldwork, also connects the Causeway to the same volcanic activity that formed Fingal’s Cave on the Scottish Hebridean island of Staffa, rock formations on the Mourne mountain range and the isle of Rùm, and magmatic activity on Skye. Previously, scientists believed the Staffa basalts had formed millions of years after the Causeway.
“Scientists reveal Giant's Causeway formed in 5.5 million years, not 13.5 million as thought.”
Dr Simon Tapster, a geochronologist at the BGS, said: “Fundamentally, what we’ve done is by piecing together this tapestry of volcanic rocks all across the North Atlantic, but focusing on Northern Ireland, we have been able to reassess a major globally impacting volcanic event. In doing that, and in reassessing the timescales, we have shown that actually it occurred in a much shorter duration.”
The findings place the formation of the Unesco world heritage site within a precise global geological context for the first time, allowing scientists to link the lava flows of Northern Ireland’s Antrim Plateau to volcanic rocks as far away as Greenland. Tapster added: “By looking at the timescales and the high resolution timeline, we’re able to match it up with various other locations, particularly in the Inner Hebrides in Scotland, the volcanics of Mull, Rum, the Isle of Skye, and taking a bigger view, looking at Greenland and the Faroe Islands.”
The new timeline dramatically revises understanding of when specific volcanic events happened in Northern Ireland, confirming that the Causeway’s distinctive columns — formed when thick lava flows cooled, contracted and cracked — are the product of a much more intense, short-lived burst of volcanic activity than previously believed.