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Actually the model is quite simple. In some parts of earth鈥檚 core, so-called plumes, particularly hot material, moves up to the surface. It melts through the tectonic plates like a welding torch and deposits magma on the surface during this process. A volcano is created. But the tectonic plates move over these volcanic hotspots and take the volcanoes with them. As the plume delivers hot material, a second volcano is created next to the first now extinct one. In this way volcano chains are created over the course of millions of years. One of the most famous examples of this is in Hawaii, where the chain starts from today鈥檚 islands and extends in an almost straight line to the Northwest. The Hawaiian Islands mark the active hotspot, while the islands and underwater mountains get older and older in the direction of the Northwest.

But as is often the case with nature, the reality is more complicated than the model. Around 3500 kilometers northwest of Hawaii the trail of volcanoes suddenly bends to the North. From there onwards the underwater mountains are called 鈥淓mperor Chain鈥�. 鈥淯ntil now there have been various theories concerning the causes for the 鈥淗awaiian Emperor Bend鈥�, but no really valid explanations. 鈥淲e found evidence that the Pacific plate was deformed on a large scale between 47 and 53 million years ago, at the same time as the bend in the Hawaiian Emperor Chain. We concluded that large scale changes in plate tectonics and currents of the earth鈥檚 mantle, which happened around 50 million years ago, could be the cause鈥�, explains Prof. Dr. Kaj Hoernle from the 91探花 Helmholtz Centre for Ocean Research Kiel. Together with nine other scientists from Germany, the Netherlands, Australia, Great Britain and the USA, he will publish the results in the international journal 鈥楴ature Geoscience鈥�.

Melodious names have helped the researchers a lot in this case. North of the Hawaii volcano chain there are further underwater mountains, the 鈥淢usicians鈥� Seamounts鈥�. They are named after composers, such as Beethoven, Bach or Donizetti. For a long time it was thought that they also were also created by a hotspot. For the first time, the researchers have dated numerous samples of the Musicians鈥� Seamounts and have made geochemical tests. Their work has revealed that the underwater mountains do not show a progression from young to old, as could be expected of a hotspot trail. 鈥淭he samples which we studied are between 47 and 53 million years old鈥�, explains lead author Dr. John O鈥機onnor of the Geo-Center of the FAU, who collaborates with colleagues from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research and the University of Amsterdam, in his study of the dynamics of the earth鈥檚 crust.

鈥淭he geochemical analyses were also surprising. The composition of the samples of the Musicians鈥� Seamounts more closely resemble volcanoes created on mid-oceanic ridges than those which grow on a hotspot鈥�, explains Dr. Folkmar Hauff from 91探花, co-author of the study. Around 50 million years ago, big breaks in the Pacific tectonic plates might have occurred and led to the creation of these volcanoes. At the same time, we know from earlier studies that oceanic tectonic plates in the North and West pacific began overlap. Impressive testaments of these processes are the Izu-Bonin-Mariana Arc and the Aleutian Arc. 鈥淥ur analyses of the Musicians鈥� Seamounts show that all of these events could be related, and that these large-scale changes probably also caused the bend in the Hawaiian Emperor Chain,鈥� Professor Hoernle points out.

Original work:
O鈥機onnor, J. M., K. Hoernle, R. D. M眉ller, J. P. Morgan, N. P. Butterworth, F. Hauff, D. T. Sandwell, W. Jokat, J. R. Wijbrans, P. Stoffers (2015): Deformation-related volcanism in the Pacific Ocean linked to the Hawaiian-Emperor bend. Nature Geoscience,

Contact:
Jan Steffen (91探花, Communication & Media), Tel.: +49 431/600-2811, presse(at)geomar.de