Kazan-rettō (火山列島)
The Japanese-owned Kazan-rettō (Volcano Islands) are an isolated group of small islands located in the
western Pacific, situated just north of the Tropic of Cancer, and lying 600 km northwest from the
Mariana Islands, 148 km southwest from the Ogasawara-shotō
(Bonin Islands) and around 1,200 km south from Tokyo. The grouping is small, consisting of a linear
chain of three islands that spans north to south across 137 km of ocean. The group, with an total land
area of 28 km², comprises the islands of Iō-jima, Kita-Iō-jima and Minami-Iō-jima.
The main — and only populated — island of the group is Iō-jima (Iwo-Jima), with an area of 21 km². The island is of flat relief, with the exception of the low and rocky dome of the extinct volcano of Suribachi that rises to 166 m at the southern end of the island. Situated approximatey equal distances north and south of Iō-jima are the two smaller islands that complete the group. Kita-Iō-jima, located 67 km to the north and slightly east, is the second largest of the islands at 6 km². The island presents a dramatic profile, rising from the sea as a heavily-eroded and steep-sided basaltic dome that reaches a height of 792 m. The third and smallest member of the Kazan-rettō is the small island of Minami-Iō-jima (less than 1 km² in area), located 58 km south of Iō-jima. Like Kita-Iō-jima, the island is uninhabited and rises from the sea as a very steep-sided and eroded cone of 970 m in height — the highest point in the whole island group.
Geologically, the islands are part of the Izu-Bonin-Mariana island arc system that extends for 2,800 km from near Tokyo to Guam in the Mariana Islands. The Kazan-rettō are situated roughly in the middle of the Izu-Marianas arc system. The IBM arc is a premier example of an inter-oceanic convergent margin. Here, the western Pacific plate is being subducted beneath that of the Philippine Sea Plate. For the other groups of islands that comprise the volcanic Izu-Bonin-Mariana arc see the Izu-shotō, Ogasawara-shotō (Bonin Islands) and the Mariana Islands.
