Globally significant volcanic event formed Giant’s Causeway, scientists find | Geology

For centuries the story has been passed down from generation to generation: how Irish giant Finn McCool built the Giants Causeway in Northern Ireland by throwing chunks of the Antrim coastline into the sea to fight his Scottish rival Benandonner.

What led to the formation of 40,000 distinct interlocking basalt columns along the coastline about 60 million years ago was not a legendary battle between two destructive giants, but intense volcanic activity during a “major globally impacting volcanic event”, scientists have revealed.

Geochronologists investigating how the Giant’s Causeway was formed discovered that it was formed in 5.5 million years, 8 million years shorter than previously estimated.

They also found that the processes that formed the Giant’s Pass were linked to a globally significant volcanic event recorded in rocks as far away as Greenland.

For the first time, they have managed to conclusively link the first lava flows on the Northern Ireland plateau to the same volcanic activity that formed the giant basalt columns in Fingal’s Cave on the Scottish Hebridean island of Staffa; these rocks were previously thought to have formed millions of years after the Gate.

Rock formations in the nearby Morne mountain range and the Hebridean island of Rùm, as well as igneous activity on Skye, may also be associated with this volcanic activity; It places the formation of the Giant’s Causeway in a more precise, global geological context for the first time, allowing scientists to establish a new timeline for volcanic activity in Northern Ireland.

Dr. geochronologist from the British Geological Survey (BGS). Simon Tapster said: “Basically what we did was bring together this fabric of volcanic rocks from all over the North Atlantic, but by focusing on Northern Ireland we were able to re-evaluate a major volcanic event that had a global impact.

“As we did this and re-evaluated the timelines, we showed that it actually happened in a much shorter period of time.”

The Giant’s Causeway is a Unesco world heritage site and has been named one of the UK’s greatest natural wonders. According to Irish folklore, Finn McCool created the passage so that he could cross into Scotland to confront the Benandonner who was threatening his homeland, but the Scot retreated to the island of Ireland, pursued by his rival, only to find the Scotsman a much larger and more impressive giant.

Legend has it that it was Finn’s quick-thinking wife, Oonagh, who saved the day. He disguised Finn as a giant baby so that, believing the baby’s father to be big enough to defeat him in a fight, Benandonner raced through the pass towards Scotland, destroying as much of the pass as possible in his path.

Although visitors to the dramatic landscape choose to believe the legend, scientists have shown that the Gorge was formed when thick molten rock rose through cracks in the earth’s crust. As the lava cooled and contracted, stress and strain built up within the rock, forcing it to fracture into mostly hexagonal columns, although some rocks have four, five, seven or more sides.

Tapster’s research is part of a wider initiative at BGS to improve understanding of the UK’s geology through better measurement of geological time in the rocks around us.

He said: “By looking at the timelines and the high-resolution timeline, we are able to match it with a variety of other locations, particularly the volcanics in the Inner Hebrides in Scotland, the volcanics on Mull, the Rum volcanics, the Isle of Skye, and we can look at Greenland and the Faroe Islands from a greater perspective.”