The submarine volcano "Fukutoku-okanoba" near Minami-iwojima erupted around 8:00 p.m. on January 18, 1986 and formed a new island by January 20. At the same time, other phenomena such as flotsam formed from pyroclastic materials, discolored ocean zones and volcanic smoke were confirmed .

Because it was possible to obtain LANDSAT/TM data from January 20, the first day the new island was formed, it was possible to monitor the condition of the new island, discolored ocean zones, the positions of flotsam and the status of volcanic smoke with regular bulletins. This data served as part of the information for a monitoring system following the eruption and for taking evacuation measures for ocean traffic.

The analytical method is shown as a flow chart in the appendix, but the unique characteristics of the method are described below.

1) We measured the position of the crater by using GCP selected from two nearby islands (Iwojima and Minami-iwojima).

2) We used the maximum likelihood method, using bands 1, 2, 3, 4, 5 and 6. Our aim was to describe the cloud classification using band 5, and classifications tempered with heat information from band 6.

3) We classified band 6 in the smoke region, and determined the relationship between smoke temperature and smoke altitude.

4) When the volcanic smoke reached altitudes where we could not distinguish the smoke from surrounding clouds by the smoke's temperature, we sampled the smoke using band 7 data slices.

1) We inferred the position of the new island's crater to be located off of Minami-iwojima's Cape Matsue (24°17'27"N, 141°S29'00"E), and the land area of the new island to be approximately 0.4km².

2) We sampled a variety of items, including the new island, discolored ocean zones, flotsam, volcanic smoke and ocean surface temperature, by the maximum likelihood method using bands 1, 2, 3, 4, 5 and 6.

3) We surmised from the temperature of the volcanic smoke that the volcanic smoke altitude reached over 2,000m.

We monitored the condition of the new island, discolored ocean zones, the positions of flotsam and the status of volcanic smoke through regular bulletins. This data served as part of the information for a post-eruption monitoring system and for taking evacuation measures for ocean traffic.

In addition, for the ocean surface temperature in the vicinity of the crater and the volcanic smoke temperature near positions directly above the crater, we verified the validity of the TM data from the close agreement between the values determined from LANDSAT/TM band 6 (19.9°C, 37.8°C) and the values determined from aircraft-mounted radiation thermometers (19.4°C, 39.4°C).