The Tokyo VAAC reported that ash plumes from Nishinoshima rose to 2.1-2.7 km (7,000-9,000 ft) a.s.l. and drifted NE and E. During an overflight on 15 June the Japan Coast Guard noted continuous activity from the central vent, including a gray-brown to black-brown ash plume rising as high as 2 km. Ejected material landed near the cone’s base. Lava from the NE side of the central vent flowed E. Steam plumes rose along the E coast where lava entered the sea, causing discolored brownish water offshore. The marine exclusion zone was defined as a radius of about 2.6 km from the island.

Geological Summary. The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

Sources: Japan Coast Guard, Tokyo Volcanic Ash Advisory Center (VAAC)