An ancient Irish volcano is challenging scientific understanding of how eruptions occur.
The secrets that lie beneath Carlingford Mountain in Co Louth could improve monitoring of its active cousins and help pinpoint when they are likely to erupt.
An international team led by scientists from Trinity College Dublin has found the common view of a volcano as being located above a vat of bubbling molten rock or magma simply waiting to explode does not always hold true.
They discovered the rock beneath Carlingford Mountain was connected to a complex “plumbing system” through which magma came and went.
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At times it pooled under the volcano as boiling liquid but other times it lingered in a semi-molten state heavy with crystallised rock, with a texture the Trinity team described as being like a “slushy” flavoured ice drink.
Mike Stock from Trinity’s School of Natural Sciences, principal investigator on the research, explained why Carlingford Mountain was so valuable to the study.
“Volcanoes are a major natural hazard but geologists struggle to understand them because we can’t take rock samples from several kilometres beneath Earth’s surface in active settings,” he said.
“Ancient extinct volcanoes in Ireland can provide really important new insights. Thanks to glaciers eroding away their overlying rocks, we’re able to directly see inside their magmatic plumbing systems.”
Colleague Jack Beckwith, a PhD student and lead author on the paper, said understanding the interchange of liquid and crystalline magma helped explain the behaviour of volcanoes.
“At Carlingford we see that magmas can actually switch between these two states over short periods in geological terms, creating opportunities for more fluid magmas to ascend and fuel eruptions.”
Carlingford Mountain on the Cooley Peninsula in Co Louth is located among hills that are fossilised remnants of magma systems that fed ancient volcanoes.
Those systems, fossilised 60 million years ago, were once linked to the same systems currently feeding active volcanoes in Iceland.
“Subsequent tectonic plate movement opened the Atlantic Ocean, pulling Ireland away from the hotspot, and causing the volcanoes to cool, solidify and eventually become extinct,” the Trinity team explained.
“Glacial erosion removed the overlying volcanic edifice, exposing the magma plumbing systems and providing a unique window deep inside the Earth.”
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Their work, supported by Research Ireland and Geological Survey Ireland, is published in the current edition of the Journal of Petrology.
Petrology studies the composition of rocks and the conditions under which they form so the team, comprising scientists from seven universities in Ireland, Britain, Northern Ireland and the United States had to take multiple samples from the Carlingford site for analysis.
Their work confirms theories on the subject but which have been difficult to prove because researchers cannot work beneath an active volcano.
