Globally significant volcanic event formed Giant’s Causeway, scientists find
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- Scientists at the British Geological Survey and Geological Survey of Northern Ireland found the Causeway's 40,000 interlocking basalt columns formed during a major globally impacting volcanic event, with geochronologists dating the entire sequence of regional volcanic activity to just 5.5 million years — 8 million years less than previously estimated.
- Dr Simon Tapster, a BGS geochronologist, said the research links the Causeway's formation to volcanic activity recorded in rocks as far away as Greenland, with the North Atlantic sea opening between Greenland and the crust of northern UK as a direct result of this event.
- Researchers for the first time definitively connected 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 previously thought to have formed millions of years after the Causeway.
- Rock formations on the Mourne mountain range, the Hebridean isle of Rùm, and magmatic activity on Skye can also be linked to the same volcanic activity, placing the Causeway within a precise global geological context for the first time.
- The columns formed when thick molten rock rose through cracks in the Earth's crust and, as the lava cooled and contracted, stress and tension forced it to fracture into mostly hexagonal shapes — though some have four, five, seven, or more sides.
Why it matters: The new 5.5-million-year window — 8 million years shorter than previous estimates — repositions the timeline of a globally significant volcanic event, directly linking Northern Ireland's geology to Scotland's Inner Hebrides, Greenland, and the Faroe Islands. For geologists, the opening of the North Atlantic and the volcanic pulse that shaped the UK coastline are now correlated with unprecedented precision, refining models of how continents rift apart.
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