A small eruption at Nishinoshima’s central crater was observed during an overflight conducted by the Japan Coast Guard on 4 October. Gray ash-and-gas plumes rose to 1.5 km (4,900 ft) a.s.l. Gas emissions from the central crater were at similar levels to those seen on 20 September, though gas emissions had increased at the fumaroles widely distributed along the E and N parts of the island. Dark reddish-brown-to-green discolored water was visible around most of the island.

Geological Summary. The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Multiple eruptions that began in 2013 completely covered the previous exposed surface and continued to enlarge the island. The island is the summit of a massive submarine volcano that has prominent peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the ocean surface 9 km SSE.

Source: Japan Coast Guard