An under sea volcanic eruption was discovered by the No. 11 Myojin-maru, fishing boat, at the point of 31° 56.7' N, 140° 00.5' F, at-cut 5 miles ENE of the Bayernaise Reefs, on the morning of Sept 17, 1952. The volcanic islet was named as the Myojin Reef after the fishing boat. Slight explosions took place incessantly and molten lava welled out on the day of discovery of the eruption, but day after day explosions became intermittent and so violent that the new islet was blown away and disappeared under the sea on Sept. 23. But the submarine volcano kept on its activity and the appearance and disappearance of volcanic reefs were repeated often. The newly-ejected pumice is dacite.
The writer intended here to sketch in broad outline the activity of the submarine volcano from the discovery of the eruption to the end of August, 1953, with special reference to fragmental products and to severe explosions. Besides, he summarized the topography and the former recorded eruptions of the submarine volcano.