(Learn more about volcanoes in an interactive feature.)
"This type of [activity produces] tiny volcanoes, possibly now active, on the old, cold subducting Pacific plate," said Hirano from his office at the Scripps Institution of Oceanography in La Jolla, California.
"This petit spot volcano theory suggests that this type of eruption can occur wherever the oceanic plate is flexed."
Geophysicist Marcia McNutt, president and CEO of the Monterey Bay Aquarium Research Institute in Moss Landing, California, wrote a commentary on the new research.
"These small volcanoesbecause of their location and the fact that there are these clear cracks that have formed due to the bending of the [tectonic] platealmost assuredly did not form by a plume," she said.
"The coincidence that it would require to have a plume just happen to be right below those cracks in the plateit's too big of a coincidence to be credible."
McNutt suggests that Hirano and colleagues have a far more likely explanation.
"Scientists used to assume that any time there was volcanic activity that was not at a plate boundary, there had to be a plume that created it," she said.
"Maybe [the petit spot theory] could be an explanation for a lot more than this chain of volcanoes," she added.
"Maybe many features on the ocean floor, which we have tried with sometimes limited success to make fit the plume theory, could actually be [caused] by this same mechanism."
Versions of a tectonic-plate "crack" theory have been around since the mid-19th century, but the new research may provide the first real-world example. Study author Hirano hopes to uncover more volcanoes that support the theory.
"We need more surveys of the ocean floor in order to answer [questions] about frequency of petit spot volcanoes," he said. "We know of only two sites."
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