Small volcanoes play an important role in clarifying the structures of tectonic plates

Researchers from Tohoku University and the Chiba Institute of Technology have painted a clearer picture of what’s happening beneath the small spot volcanoes deep in the ocean depths of the Pacific Plate. Their newly presented geological structure, which was created by Associate Professor Naoto Hirano of the Center for Northeast Asian Studies, Tohoku University and Principal Investigator Shiki Machida of the Chiba Institute of Technology, has been released. in the journal Communications Earth & Environment.

Earthquakes and volcanoes happen because the outer part of the Earth’s surface, the lithosphere, contains shifting tectonic plates. Scientists believe that the ductile asthenosphere beneath the lithosphere drives plate motion. However, the type of rocks existing in the asthenosphere, as well as the melting process of the asthenosphere, remained largely unknown.

The Petit-spot volcanoes were first recognized in 2006 near the Japan Trench. They are young, small volcanoes that erupt along fissures in the asthenosphere, just below tectonic plates. For this reason, rocks obtained from small spot volcanoes in the deep sea provide a window into the mostly unexplored asthenosphere and allow scientists to better understand the nature of plates and the theory of plate tectonics. More recently, researchers have unearthed small dot volcanoes in different trenches such as the Marianas, Tonga, Suda and Chile trenches.

The mantle rock, which retained the state and building blocks of the deep mantle, pulled into the rising magma of the small spots. The lava (the blackish part) is strongly vesicular due to its CO2-rich composition.

Hirano and Machida

To develop their structure, Hirano and Machida first evaluated all of the previous geochemical data on the small spot magmas, their surrounding geology, and the deep mantle rocks entrained in the small spot magmas. They then specified the elementary components of the lava of the small-spot to distinguish it from other volcanoes before validating that the magma of the small-spot does not form a homogeneous mixture with the carbonated magma.

The researchers also generalized that eruptions from small spots disturb the geological environment of the deep seabed. Hot lava upsets cold deep seabed sediments before the tectonic plate subducts. Plausibly, the presence of disordered sediments could prevent the extension of certain focal regions from becoming megathrust earthquakes.

Based on these results, the pair generated an image capturing the tectonic plate before subduction in the deep mantle. “Spotty eruptions disrupt the geology of the deep seafloor, and rising little-spot magma from the carbon-rich asthenosphere changes the component of the tectonic plate rocks,” says Hirano. “Until this study, little was known about changes in tectonic plates before they subducted.”

A schematic model of the plates in subduction under the volcanoes of the small spot. Hirano and Machida
Release details:

Title: The structures of the mantle under the volcanoes of Petit-spot

Authors: Naoto Hirano and Shiki Machida

Review: Earth & Environment Communications

DOI: 10.1038/s43247-022-00438-1

/Public release. This material from the original organization/authors may be ad hoc in nature, edited for clarity, style and length. The views and opinions expressed are those of the author or authors.View Full here.

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