A team of Japanese scientists has discovered a 3-million-year-old petit-spot submarine volcano in one of the oldest parts of the Pacific Plate.
The newfound petit-spot volcano near Minamitorishima Island, Japan. Image credit: Tohoku University.
Petit-spot volcanism is an eruption of very alkaline magma forming small volcanoes on the oceanic plate.
The first petit-spot volcanoes were discovered in 2006 near the Japan Trench, an oceanic trench part of the Pacific Ring of Fire off northeast Japan.
“Petit-spot volcanoes are young, small volcanoes that come about along fissures from the base of tectonic plates,” said Dr. Naoto Hirano from the Center for Northeast Asian Studies at Tohoku University and colleagues.
“As the tectonic plates sink deeper into the Earth’s upper mantle, fissures occur where the plate begins to bend causing small volcanoes to erupt.”
“The magma emitted stems directly from the asthenosphere — the uppermost part of Earth’s mantle which drives the movement of tectonic plates.”
“Studying petit-spot volcanoes provides a window into the largely unknown asthenosphere giving scientists a greater understanding of plate tectonics, the kind of rocks existing there, and the melting process undergone below the tectonic plates.”
The newly-discovered petit-spot volcano is located near Minamitorishima (Marcus) Island, Japan’s easternmost point.
It erupted approximately 3 million years ago due to the subduction of the Pacific Plate deeper into the mantle of the Marina Trench.
“We initially suspected the presence of a small volcano after observing bathymetric data collected by the Japan Coast Guard,” the researchers said.
“We then analyzed rock samples collected by the Shinkai 6500, a manned submersible that can dive to depths of 6,500 m (21,325 feet), which observed the presence of volcano.”
“The discovery of this new volcano provides and exciting opportunity for us to explore this area further, and hopefully reveal further petit-spot volcano,” Dr. Hirano added.
“This will tell us more about the true nature of the asthenosphere.”
The discovery is reported in a paper in the journal Deep-Sea Research Part I: Oceanographic Research Papers.
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Naoto Hirano et al. 2019. Petit-spot volcanoes on the oldest portion of the Pacific plate. Deep Sea Research Part I: Oceanographic Research Papers 154: 103142; doi: 10.1016/j.dsr.2019.103142
