Scientists have discovered that there is not always liquid magma beneath volcanoes
An international team of geologists has concluded that volcanoes do not always have large reservoirs of liquid magma beneath them, as had been believed for decades. A study of an ancient volcano in Ireland has shown that magmatic systems can constantly transition from a liquid state to a near-solid state and back again. According to the scientists, it is precisely these changes that may play a key role in the build-up to eruptions.
The subject of the study was Mount Carlingford in Ireland — the remains of a volcano that was active around 60 million years ago.
It was once formed above the same hot spot in the Earth’s mantle that today feeds Iceland’s volcanoes. Later, the movement of tectonic plates moved Ireland away from this zone, the volcano became extinct, and glaciers gradually eroded its summit.
As a result, researchers have been given a rare opportunity to literally peer inside an ancient magmatic system.
Details
By studying the structure of the rocks and the composition of the minerals, the scientists reconstructed the history of magma development beneath the volcano.
It turned out that the familiar picture of a huge underground chamber filled with molten rock is far too simplistic.
At various times, there were indeed areas of liquid magma beneath the volcano; however, for most of the time, the magmatic system consisted of a dense mass of crystals with only a small amount of melt. In terms of its structure, it resembled a thick iced drink rather than completely liquid lava.
Over time, this system could become more fluid again, after which the likelihood of an eruption would increase.
Why this is important
Researchers believe that similar processes occur beneath modern active volcanoes.
Since it is impossible to take rock samples from depths of several kilometres beneath an active volcano, ancient volcanoes provide a unique ‘window’ into the Earth’s interior.
The new model will help us better understand how magmatic systems evolve and why an eruption begins at a particular point in time.
According to the authors of the study, Carlinford in Ireland can be considered a natural analogue of Iceland’s modern volcanoes.
Because glaciers have stripped away the upper part of the ancient volcano, scientists have been able to study its internal structure — something that today lies hidden deep beneath active volcanoes.
Source
Study: J. Beckwith et al. Transient Liquid- and Solid-dominated Inflation of an Upper Crustal Magma Chamber: Insights from the Carlingford Complex (Ireland).
Journal: Journal of Petrology (2026).