Ardnamurchan magma mystery solved

A volcano on the Scottish peninsula thought to have three successive magma chambers only has one single chamber say researchers.

The 58 million year old Ardnamurchan volcano is an iconic site for the study of rocks and structures in the core of a volcano, and since the early days of modern geology it was believed to have three successive magma chambers that fed hundreds of thin arcuate basalt intrusions (cone sheets) that are exposed all over the peninsula.

However, researchers from the Universities of Uppsala, Quebec, Durham and St Andrews have used a 3D model of the subsurface beneath today’s land surface to challenge this concept. According to their model, the volcano has a single but elongate magma chamber.

“It came as a bit of a surprise to us that there is still so much to learn from a place that has received so much attention by geologists,” said Dr Steffi Burchardt, a senior lecturer at Uppsala.

“Modern software allows visualising field measurements in 3D and opens up a range of new perspectives. After projecting hundreds of cone sheets in the computer model, we were unable to identify three separate centres,” Burchardt added. “The cone sheets instead appear to originate from a single, large and elongate magma chamber about 1.5km below today’s land surface.”

The magma chamber was up to 6km long and has the shape of an elongate saucer. It is similar to those found in volcanoes in Iceland, and have been detected in the North Sea bedrock.

“Ardnamurchan’s new magma chamber is hence much more realistic considering everything we have learned about Ardnamurchan and other extinct and active volcanoes” said Professor Valentin Troll, chair in petrology at Uppsala.

The team published their work in Scientific Reports.

Ardnamurchan 3D cone sheer architecture explained by a single elongate magma chamber http://www.nature.com/srep/2013/131008/srep02891/full/srep02891.html