The subduction process is related to the production of volcanoes in Japan as the downgoing oceanic slab undergoes dehydration at depths of roughly 90 to 100 km (55 to 60 mi) beneath the overriding plate.

[5] Water in the structure of hydrated minerals interact with the upper mantle, lowering its melting point.

As the mantle begins to melt, its density decreases and rises through the upper crust, forming a volcanic vent.

[6] The island consists of two basaltic-to-andesitic stratovolcanoes, the highest measuring 737 meters (2,418 ft) above sea level.

Around the Matsumae Peninsula, heavy ash fall from the eruption blocked out the sun and plunged villages into darkness.

One hundred and forty people were killed while 53 vessels and 83 houses were lost to the waves in Tsugaru on the island of Honshu.

[10][11] On the Korean Peninsula, the tsunami slammed into the east coast, flooding nine villages and destroying many fishing vessels.

[21] Initially proposed in 1972 by Hiroo Kanamori, these events release seismic energy in long periods.

However, there has been no attempt to conduct submarine surveys in the Sea of Japan to confirm the claim of seismic activity along the plate boundary.

[21] A landslide and debris avalanche involving a subaerial and submerged portion of the volcanic island has been the more accepted source mechanism of the large tsunami.

[15] This would make it the second largest historical volcanic sector failure in history, alongside the 1888 eruption of Ritter Island.

[24] A more recent study in 2019, however, stated that the slide volume was 2.2 km3 (0.53 cu mi), a significant difference from the 2001 research.