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Report on Fukutoku-Oka-no-Ba (Japan) — June 2016


Bulletin of the Global Volcanism Network, vol. 41, no. 6 (June 2016)
Managing Editor: Edward Venzke. Edited by A. Elizabeth Crafford.

Fukutoku-Oka-no-Ba (Japan) Continued intermittent plumes of discolored water through April 2014

Please cite this report as:

Global Volcanism Program, 2016. Report on Fukutoku-Oka-no-Ba (Japan) (Crafford, A.E., and Venzke, E., eds.). Bulletin of the Global Volcanism Network, 41:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN201606-284130



24.285°N, 141.481°E; summit elev. -29 m

All times are local (unless otherwise noted)

An explosion above the water surface from the submarine Fukutoku-Oka-no-Ba volcano was observed by the Japanese Coast Guard on 3 February 2010, and eruption alerts continued into early April of that year (BGVN 35:02). Although intermittent plumes of water discoloration after that indicated some level of ongoing activity through April 2014, the last observation of pumice on the sea surface was on 14 April 2010.

This trachyandesitic volcano is located 5 km NE of the Japanese island of Minami-Ioto, about 1,275 km S of Tokyo in the Izu-Bonin arc (figures 11 and 12). The National Catalogue of the Active Volcanoes of Japan, monthly reports by the Japan Meteorological Agency (JMA), and information tables and photographs prepared by the Japan Coast Guard (JCG) and Japan Maritime Self Defense Force (JMSDF) were the data sources for this report. A summary of the observations recorded during site visits made by Japanese authorities between April 2010 and October 2015 is given here, and additional details are provided in the table at the end of the report (table 3).

Figure (see Caption) Figure 11. Submarine topographic map of the Fukutoku-Oka-no-Ba area. Image date not provided but it appears to pre-date the February 2010 explosion. The island above sea level at bottom is Minami-Ioto. Fukutoku-Oka-no-Ba is 5 km N and slightly E. The NW-SE elongate submarine volcano is Kita-Fukutokutai; the Kaijin Knoll is the northernmost edifice. Courtesy of Japan Coast Guard (from National Catalogue of the Active Volcanoes in Japan).
Figure (see Caption) Figure 12. Submarine topographic map of Fukutoku-Oka-no-Ba after the February 2010 eruption (specific date not provided). Courtesy of Japan Coast Guard (from National Catalogue of the Active Volcanoes in Japan).

Observations from February 2010 through April 2011. On 3 February 2010, a 100-m-high ash and steam eruption emerged from the sea. Floating pumice was later observed on 14 April 2010 (referred to as "floating objects" in the translation of JMA and JCG tables). Discolored water continued to be observed around the volcano for the rest of 2010. Activity from multiple vents created blue-white, milky-white, and greenish-brown plumes of discolored seawater a few hundred meters wide that drifted as far as 2,700 m. In January 2011, blue-white and creamy-colored water plumes from multiple vents drifted NE in a fan shape approximately 500 m across (figure 13). Discolored water plumes were also observed on 8 February and 12 April 2011.

Figure (see Caption) Figure 13. Blue-white and greenish brown discolored seawater at Fukutoku-Oka-no-Ba on 19 January 2011. The source appears to be from multiple vents. The fan shape extends about 500 m NE of the vent source. Minami-Ioto is at the upper left. Courtesy of JMSDF (Japan Maritime Self Defense Force).

Observations from January 2012 through August 2012. Inspections of the volcano in May, July, August, and November 2011 revealed no discolored water plumes or floating objects at the site. A 150-m-diameter plume was visible again on 27 January 2012. Observations on 9 March and 19 April 2012 confirmed the continued presence of discolored water. On 11 May 2012, a 50 x 150 m milky-green-colored area was photographed by the JCG (figure 14). Additional observations of discolored water plumes were made on 13 June, 15 June, and 9 August 2012; no visits were made during September-November 2012.

Figure (see Caption) Figure 14. Milky-green discoloration of seawater at Fukutoku-Oka-no-Ba on 11 May 2012. The dimensions of the greenish plume are about 50 x 150 m. Courtesy of TRCGH (Third Regional Coast Guard Headquarters, JCG).

Observations between December 2012 and April 2014. Green water was originating from multiple locations within a 1,000-m-diameter plume on 11 December 2012. Milky-white, bluish-white, and yellow-brown discoloration of seawater from multiple sources was again observed on 22 January 2013 (figure 15).

Figure (see Caption) Figure 15. Milky-white and bluish-white discoloration of seawater from multiple vents on 22 January 2013 at Fukutoku-Oka-no-Ba. Courtesy of TRCGH (JCG); color adjusted.

Plumes were observed twice in March (8 and 26), April (10 and 21), and on 12 May of 2013 but not during visits in June and July. They were seen again on 21 August and 27 September. No visits were made in October and November, but a 1,850-m-long plume drifting E was observed on 16 December 2013 by JMSDF. The last confirmed observations of discolored water plumes were on 29 January and 28 April 2014 by the JMSDF and JCG. They continued to visit the site nearly every month until October 2015, with no further observations of discolored water plumes. No further reports were made after October.

Table 3. Summary of observations made at Fukutoku-Oka-no-Ba between March 2010 and April 2014 by Japanese authorities. The Japan Coast Guard continued to visit the site almost every month through October 2015 with no further reports of water discoloration, and it was not mentioned after that date in monthly JMA reports. Sources: JMA*= National Catalogue of the Active Volcanoes in Japan, JMA= Monthly Summary Report, Japan Meteorological Agency, JMSDF= Japan Maritime Self Defense Force, TRCGH= Third Regional Coast Guard Headquarters, JCG=Japan Coast Guard.

Visit Date Discolored Water Dimensions Description Source
Mar 2010 Yes -- -- JMA*
14 Apr 2010 Yes 360 x 2700 m, SW Blue-white, milky-white and pale green, multiple vents, floating objects observed JMA*/JMSDF
26 Apr 2010 Yes -- Fan-like, multiple vents, blue and milky white, no floating objects observed JMA*/TRCGH
16 May 2010 Yes 100 m radius Milky, multiple vents, no floating objects observed JMA*/TRCGH
04 Jun 2010 No -- -- TRCGH
17 Jun 2010 Yes 100 x 200 m, EW Blue-white, and green, multiple vents JMA*/JMSDF
Jul 2010 Yes -- -- JMA*
17 Sep 2010 No -- -- JMSDF
18 Sep 2010 No -- -- JCG
29 Sep 2010 Yes 100 x 500 m NE Light blue, thin milky JMA*/JCG
Oct 2010 Yes -- -- JMA/JCG
Nov 2010 Yes -- -- JMA/JCG/JMSDF
18 Dec 2010 Yes 280 x 1,800 m Blue-white and green, multiple active vents, drifting S JMA/JMSDF
19 Jan 2011 Yes 500 m NE Multiple vents, Blue-white, milky white, greenish brown, fan shape JMA*/JCG
24 Jan 2011 Yes -- -- JMSDF
28 Jan 2011 Yes -- Creamy-white JMSDF
08 Feb 2011 Yes 50 x 2000 m NE Multiple vents, blue-white, green JMA*/JCG
12 Apr 2011 Yes 100 m radius Milky-white JMA*/JMSDF
May 2011 No -- -- JMA*
Jul 2011 No -- -- JMA*
06 Aug 2011 No -- -- TRCGH
16-17 Nov 2011 No -- -- JMA*/JCG
27 Jan 2012 Yes 150 m diameter Milky-white, yellow-green JMA*/TRCGH
28 Jan 2012 Yes 100 m diameter Milky-white, yellow-green, thin blue TRCGH
30 Jan 2012 Yes 60 x 300 m N Light green, milky TRCGH
09 Mar 2012 Yes 50 x 200 m Dark milky white, pale blue JMA*/JCG
19 Apr 2012 Yes 30 m diameter Milky JMA*/TRCGH
11 May 2012 Yes 50 x 150 m; 1500 m SW Milky; thin blue JMA*/TRCGH
16 May 2012 Yes -- Slight thin white TRCGH
13 Jun 2012 Yes -- Slight pale blue-white TRCGH
15 Jun 2012 Yes 50 m Pale blue-white JMA*/JMSDF
09 Aug 2012 Yes 200 x 300 m Multiple vents, blue-white JMA/JMSDF
23 Aug 2012 No -- Poor visibility JCG
11 Dec 2012 Yes 1000 m diameter Multiple vents, thin green JMSDF
22 Jan 2013 Yes 100 x 300 m Multiple vents, milky-white, blue-white and light green-brown TRCGH/JMSDF
08 Mar 2013 Yes 1000 m [500 m] diameter Milky white and blue JMSDF [JMA]
26 Mar 2013 Yes 500 x 1500 m Milky white, pale blue and pale green JCG
10 Apr 2013 Yes 630 m radius Multiple vents, green JMA/JMSDF
21 Apr 2013 Yes 50 m radius Milky-white JMA/JCG
12 May 2013 Yes 50 x 400 m S Milky-white JMA/JCG
25 Jun 2013 No -- -- JMA/JMSDF
29 Jun 2013 No -- -- JMA/JCG
17 Jul 2013 No -- -- JMA/JCG
21 Aug 2013 Yes -- Faint discoloration JMA/JMSDF
24 Aug 2013 No -- -- JMA/JCG
27 Sep 2013 Yes 450 m radius Green water and white bubbles JMA/JMSDF
16 Dec 2013 Yes 1850 m E Multiple vents, green JMA/JMSDF
28 Dec 2013 No -- -- JMA/JCG
13 Jan 2014 No -- -- JMA/JCG
29 Jan 2014 Yes -- -- JMA/JMSDF
02 Feb 2014 No -- -- JMA/JCG
28 Apr 2014 Yes -- -- JMA/JCG

Reference. Japan Meteorological Agency, 2013, National Catalogue of the Active Volcanoes in Japan (Fourth Edition, English Version), Tokyo, Japan (http://www.data.jma.go.jp/svd/vois/data/tokyo/STOCK/souran_eng/menu.htm).

Geological Summary. Fukutoku-Oka-no-ba is a submarine volcano located 5 km 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.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); Japan Coast Guard (JCG) Volcano Database, Hydrographic and Oceanographic Department, 3-1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8932, Japan (URL: http://www1.kaiho.mlit.go.jp/GIJUTSUKOKUSAI/kaiikiDB/kaiyo24-2.htm).