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Discovery of Direct Evidence to Support that Magma Exists Beneath the Oceanic Plate

Research Press Release | November 06, 2014

  • Location where lava was collected (offshore of the Tohoku region). This area is located immediately before the oceanic plate subducts under the Japanese Archipelago. Stress from the plate bending is thought to cause cracks in the oceanic plate. While igneous activity has never been predicted in this area before, if magma exists just beneath the oceanic plate, it is a possibility that magma flows to the seabed through a crack.
    Location where lava was collected (offshore of the Tohoku region). This area is located immediately before the oceanic plate subducts under the Japanese Archipelago. Stress from the plate bending is thought to cause cracks in the oceanic plate. While igneous activity has never been predicted in this area before, if magma exists just beneath the oceanic plate, it is a possibility that magma flows to the seabed through a crack.
  • Data on temperature and depth (white circles) obtained from fragments of the oceanic plate (xenolith), which were entrained by magma. Since the oceanic plate which subducts underneath Japan is extremely old, it was thought to have a cold thermal structure (blue line). However, the oceanic plate beneath the petit-spot volcanoes was found to have a hot thermal structure (red line) as if newly formed.
    Data on temperature and depth (white circles) obtained from fragments of the oceanic plate (xenolith), which were entrained by magma. Since the oceanic plate which subducts underneath Japan is extremely old, it was thought to have a cold thermal structure (blue line). However, the oceanic plate beneath the petit-spot volcanoes was found to have a hot thermal structure (red line) as if newly formed.
Press Release
Key Points

・Direct proof that magma exists beneath the oceanic plate—which has been long predicted—was confirmed.

・It was also proven that it erupted for several million years.

・It is now proposed that magma exists beneath oceanic plates around the world.
Overview The outer layer of the Earth is covered by slowly moving rock layers called plates. Movement of these plates causes earthquakes, magma eruption, and development of geographical features. The plates and the mantle under them are comprised of rock, and when the plates move, intense friction is generated between both layers. If magma existed between them, it would act like a lubricant, and would more easily explain how the plates can move smoothly. With this in mind, the possibility that magma exists beneath oceanic plates has long been suspected, and now there is evidence to support the claim of this extremely elusive magma.
Inquiries

Junji Yamamoto, Associate Professor, Hokkaido University Museum

TEL: +81-11-706-4733

FAX:+81-11-706-4029

E-mail: jyama@museum.hokudai.ac.jp

Japanese

Link

 海洋プレート直下にひそむマグマの証拠を発見
Publications Melt-rich lithosphere-asthenosphere boundary inferred from petit-spot volcanoes (Geology, 2014.9.26)

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