Map of the Hawaiian Emporer bend.

Map of the Hawaiian Emporer bend.

27.04.2015

Composers provide explanation for Hawaiian Emporer bend

International team of researchers finds evidence of large-scale tectonic changes in the Pacific taking place 50 million years ago

27. April 2015/Kiel. From Hawaii to Kamchatka a chain of extinct volcanoes, lying mostly under water, stretches across the Pacific. This Hawaiian Emperor Chain is the trail left by a volcanic hotspot. But why does it change its direction halfway through? An international research team, with the participation of the GEOMAR Helmholtz Centre for Ocean Research Kiel, the Alfred Wegener Institute, the Helmholtz Centre for Polar and Marine Research and the Friedrich-Alexander University Erlangen-Nürnberg (FAU), have found an explanation in large-scale tectonic changes that took place around 50 million years ago. The study will appear in the international journal Nature Geosciences.

Actually the model is quite simple. In some parts of earth’s 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’s 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 “Emperor Chain”. “Until now there have been various theories concerning the causes for the “Hawaiian Emperor Bend”, but no really valid explanations. “We 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’s mantle, which happened around 50 million years ago, could be the cause”, explains Prof. Dr. Kaj Hoernle from the GEOMAR 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 ‘Nature Geoscience’.

Melodious names have helped the researchers a lot in this case. North of the Hawaii volcano chain there are further underwater mountains, the “Musicians’ Seamounts”. 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’ 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. “The samples which we studied are between 47 and 53 million years old”, explains lead author Dr. John O’Connor 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’s crust.

“The geochemical analyses were also surprising. The composition of the samples of the Musicians’ Seamounts more closely resemble volcanoes created on mid-oceanic ridges than those which grow on a hotspot”, explains Dr. Folkmar Hauff from GEOMAR, 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. “Our analyses of the Musicians’ 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,’ Professor Hoernle points out.

Original work:
O’Connor, J. M., K. Hoernle, R. D. Müller, 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, https://dx.doi.org/10.1038/ngeo2416

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

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