A major eruption started at the Japanese submarine Fukutoku-Oka-no-Ba volcano at around 21:20 UTC on August 12, 2021, and continued into August 13.
According to the Tokyo VAAC, volcanic ash was rising up to 16.4 km (54 000 feet) above sea level at 23:50 UTC and heading SSW toward the Philippines.1
Their latest VA Advisory, issued at 06:00 UTC, confirmed ash was still rising from the volcano at 05:20 UTC.
Eruption at Fukutoku-Oka-no-Ba submarine volcano. Image credit: JMA/Himawari-8, NII/NICT, TW. Acquired at 05:20 UTC on August 13, 2021
Eruption at Fukutoku-Oka-no-Ba submarine volcano. Image credit: NASA/NOAA SuomiNPP/VIIRS, TW. Acquired on August 13, 2021
The last eruptive episode at this volcano started on February 3, 2010, and lasted to ~April 8, 2010 (VEI 1).
Numerous eruptions were recorded in 20th century, two of them VEI 3 and three VEI 2.
The Japan Coast Guard has stated that "the eruption was so large that it could not be observed in close proximity," and is calling for caution on vessels navigating and flying aircraft in the vicinity.3
An observation conducted by the Japan Coast Guard in June confirmed that volcanic activity had become more active, such as discoloration of the surrounding sea surface.
火山雷って言うらしい pic.twitter.com/LOfLYIKToS— あんだーそん (@misoka_fumituki) August 13, 2021
「福徳岡ノ場」14日21時～22時の様子 今日も火山雷見えました pic.twitter.com/oiprGmUAu8— あんだーそん (@misoka_fumituki) August 14, 2021
Fukutoku-Oka-no-ba is a submarine volcano located 5 km (3.1 miles) NE of the pyramidal island of Minami-Ioto. Water discoloration is frequently observed from the volcano, and several ephemeral islands have formed in the 20th century.
The first of these formed Shin-Ioto ("New Sulfur Island") in 1904, and the most recent island was formed in 1986.
The volcano is part of an elongated edifice with two major topographic highs trending NNW-SSE, and is a trachyandesitic volcano geochemically similar to Ioto.2
1 Tokyo VAAC - VA ADVISORY DTG: 20210813/0600Z - FUKUTOKU-OKA-NO-BA 284130
2 Fukutoku-Oka-no-Ba - Geological summary - GVP
3 Eruption at Fukutoku-Okanoba, a submarine volcano near Iwo Jima, for the first time in 11 years - NHK
Featured image: Eruption at Fukutoku-Oka-no-Ba submarine volcano. Image credit: JMA/Himawari-8, NII/NICT, TW. Acquired at 05:20 UTC on August 13, 2021