![A collage of three images. The images show a man standing on the research ship, a close-up of the dredge being pulled into the sea and a close-up of the dredge.<address>© Alessio Sanfilippo</address>](http://www.uni-muenster.de/news/data/img/2024/08/14234-7cTd5Zc8-webL.jpg)
Driving force of the Iceland plume reconsidered
Researchers around the world investigate the dynamic processes in Earth’s deep interior, hundreds to thousands of kilometers below the surface. These processes drive plate movements and volcanism but still keep many secrets. As part of an international team, researchers from the University of Münster were the first to investigate rocks rising from the deep Earth– the so-called Iceland plume – and measure its chemical composition. The studied rocks are exposed at the Mid-Atlantic Ridge – which is part of the globe-encircling mid-ocean ridge system – more than thousand kilometers south of Iceland. The researchers discovered that the buoyancy force of the upwelling mantle current under Iceland is not, as previously assumed, caused only its high temperature, but also by its chemical composition. The findings have been published in “Nature Geoscience”.
These analyses show that the investigated peridotites have melted more than one billion years ago, which made them lighter, and thus more buoyant than the ambient mantle. Hence the composition, and not only the temperature, is a major factor for the low density of the Iceland plume, and triggers its upwelling from Earth’s deep interior. When they reach the shallow mantle (less than ca. 100 km depth), the rocks of the Iceland plume partially melt again and produce enormous volumes of magma, which triggers volcanic eruptions, on Iceland and along the Mid-Atlantic Ridge south of Iceland. These massive amounts of lava have built up a topographical swell in the entire North Atlantic, with Iceland on its top emerging above sea level. In contrast, the rest of the Mid-Atlantic Ridge lies several thousand metres below sea level. “Our findings also suggest that compositional variations may be responsible for periodic changes in the upwelling velocity of the rising plume. These led to variations in magma production and have produced the characteristic morphology of the ocean floor over a length of several hundred kilometers south of Iceland. Changes in seafloor topography may have also influenced the deep-water flow in the North Atlantic,” says Andreas Stracke. The researchers expect that their new findings will change the current view of the buoyancy forces of deep mantle plumes – which trigger the largest volcanic eruptions on Earth – and the interior forces that sustain Earth as a dynamic planet in general.
The researchers’ work received financial support from the German Research Foundation (DFG), from the Italian Programma di Rilevante Interesse Nazionale and from the Russian Foundation for Basic Research.
Original publication
Sanfilippo A., Stracke A., Genske F., Scarani S., Cuffaro M., Basch V., Borghini G., Brunelli D., Ferrando C., Peyve A. A., Ligi M. (2024). Upwelling of melt-depleted mantle under Iceland. Nature Geoscience. DOI: 10.1038/s41561-024-01532-z