A team of researchers has for the first time reproduced the chemical processes at the origin of the impressive geometric columns made from volcanic rocks, found in Northern Ireland and precisely known as the Giant’s Causeway.
The Giant’s Causeway is distinguished by thousands of hexagonal columns falling towards the sea. It is known that they are formed under the effect of hot magma that cools and contracts in the rock. But what is the temperature threshold? So far, the answer was not very clear. A team from the University of Liverpool in the UK now thinks they have the answer: between 840 and 890 degrees Celsius, which is just below the point where the magma crystallizes in basalt at around 980 degrees Celsius.
“The temperature at which the magma cools to form these columnar joints is an issue that has fascinated the world of geology for a very long time,” says one of the researchers, volcanologist Yan Lavallée. To reach this conclusion, scientists used basaltic columns extracted from the Eyjafjallajökull volcano in Iceland. Gripped in forceps, the samples were heated to over 1000 degrees Celsius before being cooled in the lava.
Geologists now have a good idea of the warmth of the Giant’s Causeway rock when it began to divide into these strange forms 50 to 60 million years ago. Similar sites can also be found in Iceland, the United States and even Mars. Different cooling rates and other factors can also produce columns of different sizes and shapes.
“These experiments were technically very difficult, but they clearly demonstrate the power and significance of thermal contraction on cooling rock evolution and fracture development,” says team member Anthony Lamur.
In addition to answering a long-standing question about the formation of these rocky wonders, the research could now help experts better understand how heat travels on the surface of the Earth and how the extraction of geothermal energy could be more effective.