Bonin Islands  Source  Whalesite

      4.12 Ogasawara Gunto (Bonin Islands) (27°09'N., 142°05'E.) consists of numerous islands and islets lying SSE of Izu Shichito, extending from 27°45'N, to 26°30'N. This group is divided into three main groups; from N to S they are Mukoshima Retto, Chichishima Retto, and Haha Retto. Nishino Shima, an isolated island, lies about 70 miles W of Chichi Shima. It is reported (2014) this island is undergoing a volcanic eruption.

      Ogasawara Gunto is volcanic and has many hills and peaks. The valleys are steep and deep and there are few flat places. The land is mostly rock, but it is covered by black soil and a number of areas are suitable for agriculture.

      A mountain range runs N and S through the islands. Its peaks are barren and are mostly bare rocks, but grass and small trees are found in some places. Tropical vegetation, such as hemp and palm, is found on the mountain sides.

Mukoshima Retto

      4.13 Mukoshima Retto (27°37'N., 142°11'E.) is located at the N end of the Ogasawara Gunto, about 156 miles SE of Sofu Gan. The principal islands of this chain include Kitano Shima, Muko Shima, Nakadachi Shima, and Yome Shima, in that order from N to S.

      Tides — Currents. — In the Mukoshima Retto area the flood tidal current sets, in general, WSW at a rate of 0.5 to 2.3 knots, and the ebb tidal current sets E at a rate of 1 to 3 knots, changing directions at HW and LW.

      In the channel between Kitano Shima and Muko Shima, the flood current sets SW at a maximum rate of 2.33 knots. In the E part of this channel the ebb current sets E at a maximum rate of 3.5 knots.

      In the channel between Muko Shima and Harino Iwa, 0.7 mile SSE, the ebb sets E and the flood current sets W; both are considerable.

      North of Yome Shima the flood current sets N, between 0.11 and 0.12 mile offshore, without reference to the ebb or flood tides when the tide is a maximum. South of the island the ebb current sets mostly E.

      Kitano Shima (27°43'N., 142°06'E.) is located at the NW end of the Mukoshima Retto. Dangerous rocks are scattered to the NE of Kitano Shima. Ichino Iwa, lying 1.5 miles NNE of Kitano Shima, is the farthest N of the rocks. The tidal currents are strong among these rocks.

      4.14 Muko Shima (27°41'N., 142°08'E.), the largest island in Mukoshima Retto, lies 2 miles SSE of Kitano Shima. O Yama, the highest point on the island, rises to 88m in the E part of the island. Minamihama, on the SW side of the island, provides good anchorage for small vessels with local knowledge. There are many rocks in the bay that are dangerous when SW winds prevail, due to high swells and waves.

      Harino Iwa, 0.7 mile SSE of Muko Shima, rises to a height of 136m in the N part and 80m in the S part.

      Nakadachi Shima (Nakodo Shima) (27°38'N., 142°11'E.), located 2.5 miles SE of Muko Shima, has two peaks, Tsurugi Yama and Byobu Yama, that rise to a height of 121m and 155m, respectively.

      Fukuro Minato is a small rock-infested bay that penetrates the island’s S side. It will protect small vessels with local knowledge from all except S winds.

      Yome Shima (27°30'N., 142°12'E.), located 7 miles SSE of Nakadachi Shima, is mostly rocky and precipitous, but there are small beaches on either side of the S extremity of the island. There is a small open bay on the NE side of the island where landing can be affected; this beach is steep and there are numerous above-water and sunken rocks.

      Yome Shima rises to a height of 67m and Ushiro Shima, off the E side, and Mae Shima off the SW side, rise to heights of 46m and 127m, respectively. There are several above-water rocks in the vicinity of Yome Shima and a rocky patch, with a depth of 14.6m, lies 0.4 mile W of Mae Shima.

      4.15 Chichishima Retto (27°06'N., 142°12'E.) is a group of islands lying 18 miles S of Yoma Shima; the three principal islands, from N to S, are Ototo Shima, Ani Shima, and Chichi Shima. These islands fall in line 10 miles long.

      These islands, surrounded by several islets, are volcanic and mountainous; their coastlines consist mostly of steep cliffs, except for one section of Chichi Shima. Landing places are few and there are always high waves along the E coast.

      Tides — Currents. — To the N and S of Chichishima Retto, and between the islands, the flood current sets W and the ebb current sets E with considerable velocity, turning at HW and LW. On the E and W coast of the island chain, the currents flow N and S following the contours of the islands. In the Anishima Seto. the ebb current sets E at a rate of 4.5 knots and the flood sets W at 2.25 knots; rips occur at ebb tide.

      Between Chichi Shima and Nishi Shima, the flood current sets SW or NW at a rate of 0.8 knot and the ebb current sets ENE at a rate up to 1 knot. Between Nishi Shima and Hyotan Shima the flood current sets NW and the ebb current sets SE; the rate of each is 1.5 knots.

      Ototo Shima (27°10'N., 142°11'E.), the farthest N of Chichishima Retto, rises to a height of 229m in the S part. The coast is comprised of steep cliffs, but there are small beaches on the W side. A landing place is situated close S of Kitano Hana, the NW extremity of Ototo Shima.

      Mago Shima, 134m high, is precipitous and covered with grass; it lies 0.35 mile NE of Ototo Shima.

      Kito Iso, a flat rock 2m high, lies 0.2 mile N of Mago Shima.

      4.16 Ani Shima (27°07'N., 142°13'E.), a mountainous rocky island 254m high, lies close S of Ototo Shima. The two islands are separated by Ototoshima Seto, a shallow channel that is unsafe even for small craft.

      Ani Shima has few trees and its landscape is desolate; its shores are steep cliffs. The NE coast has many indentations, but it is deep, beset with waves, and lacks a safe area for anchorage.

      Takinoura Wan is located on the SW coast; it lies between Sujiiwa Misaki and Hakidashi Hana, 1 mile SE. It is protected from all except SW winds, which bring in swells and waves. Vessels can anchor in Takinoura Wan, in depths of 10 to 42m, sand. A sunken rock, 10m deep, lies 0.22 mile NW of Hakidashi Hana.

      Chichi Shima (27°04'N., 142°12'E.) lies S of Ani Shima and is separated from that island by Anishima Seto. Chichi Shima is the largest and farthest S of Chichishima Retto group, and is the principal island of Ogasawara Gunto. The island is 4 miles long in a N to S direction and has a width of 3 miles. The highest peak, 327m high, is located near the center of the island. The W part of the island is lower, but more uneven than the E part. The E and S coast are smooth with steep cliffs, but there are some sandy beaches toward the head of the coves.

      Tatsumi Wan indents the SE coast and Maruen Wan and two other bays indent the S coast. However, all of them are open and there is no place for a vessel to land or moor. The SW coast of the island is also indented with several small shallow bays that have many drying rocks.

      4.17 Futami Ko (27°05'N., 142°12'E.), situated on the NW coast of Chichi Shima, is entered between One Saki and Yayo Saki, 0.85 mile S. The bay extends about 1.3 miles NE of a line between the entrance points. Futami Ko is protected from the S by a breakwater extending W from the shore across Futami Iwa, 11m high, to the edge of the drying reef 0.24 mile NE of Omuga Breakwater; a light stands at its head.

      This is a Quarantine Port, a Port of Entry, and a Local Port.

      This harbor provides the best anchorage in Ogasawara Gunto. The W and S part of the bay is encumbered with submarine cables, anchorage is confined to the N and E parts of the bay, in depths of 37 to 44m. The quarantine anchorage is centered about 0.5 mile ENE of Yayo Saki.

      Caution. — Kuchino Se, with a depth of 3.4m, is located near the center of the entrance to Futami Ko. There are other obstructions and dangers in the bay which may best be seen on the chart.

      Nishino Shima (27°15'N., 140°53'E.), the farthest W of the Ogasawara Gunto group, lies 70 miles WNW of Chichi Shima. It is a flat island, 24m high, covered with grass. There is usually a heavy surf on all sides of the island. When seen from the

      NW at 10 miles, it appears as two islets. Nishino Shima is reported to be radar conspicuous at 14 miles.

      Discolored water was reported (1987) 16 miles SSW and 43 miles ESE of Nishino Shima.

Hahashima Retto

      4.18 Hahashima Retto (26°38'N., 142°08'E.) is a group of islands lying about 20 miles S of Chichi Shima that cover an area of 11 miles long in a N to S direction. This group consists of the principal island Haha Shima, which lies at the N end of the group, and five smaller islands. The islands’ coasts are steep and cliffy. In general, the water is deep near the shore, but ridges are found within 0.5 to 1 mile offshore, in the N and middle parts of the islands. These islands lie at the S extremity of a 0.1 mile bank that encompasses all the islands of Ogasawara Gunto, with the exception of Nashino Shima.

      Tides — Currents. — The tidal currents in Hahashima Retto set W with rising tide and set E with the falling tide. On the E and W sides, the currents set S and N with the rising and falling tides, respectively, and generally follow the shape of the land. The current NW of Innui Saki is considerable and wave patterns occur; NW of Sawara Ne, the ebb current sets N at 1.75 knots. Near Okinohae and Jinohae, the tidal currents are especially strong; the ebb current sets NNE at a rate of 1.4 to 3.5 knots and the flood current sets SW to W at a rate of 1 to 2 knots. These currents change at HW and LW. There are tide rips in this area.

      One mile off Higashi Saki, off the E coast, the flood current sets SE and the ebb current sets SW, both at a rate of 1 knot.

      At the center of Aneshima Seto the flood current sets WSW at a maximum rate of 3.5 knots and the ebb current sets SE. Between Ane Shima and Imoto Shima the current always flows S or W at a maximum rate of 1 knot.

      4.19 Haha Shima (26°39'N., 142°09'E.) is the largest and N island in Hahashima Retto; it is 7 miles long in a N to S direction and has a maximum width of 2.25 miles. Chibusa Yama, 462m high near the center of the island, is the highest peak of the mountain range which extends N and S.

      Inui Saki, the N extremity of the island, is a cliffy point 190m high. Jinohae, 2.1m high, and Okinohae, 1.8m high, lie 0.58 mile and 0.65 mile NNW, respectively, of Inui Saki; Oni Iwa, 91m high, lies 0.18 mile NNW of the same point.

      Kita Minato is entered between Inui Saki and Kita Misaki, a point 1 mile SE. A vessel of 2,734 gt has anchored in the bay, with Kita Misaki bearing 068°, 0.3 mile distant, in a depth of 29m, sand. However, tidal currents are strong and during W winds, swells and waves are heavy and it is occasionally unsuitable for anchorage; at times strong winds blow off the mountains. A sunken rock, 12.8m deep, is located about 0.3 mile NW of Kita Misaki.

      Gagyu Kaku, a steep cliffy point 136m high, located 1.25 miles ESE of Kita Misaki, is the N entrance point of Higashi Minato. Sekimon Saki, the S entrance point of the bay, is a rocky cliff 130m high; it lies 0.75 mile SSE of Gagyu Kaku.

      Higashi Minato is protected against winds, except from the E, by the high cliffs of the shore. A good anchorage, in 22m, sand, is situated with Higashi Yama bearing 354° and Gagyu Kaku bearing 054°. Anchorage can be taken farther out, in 29m, with Higashi Yama bearing 347°.

      Okuzure Wan is an open bay entered between Sekimon Saki and Higashi Saki, a rocky point that rises to a height of 128m close inland, located 2 miles SE.

      This bay is protected from SW to NW winds, but swells will enter from the E.

      Anchorage. — A temporary anchorage is situated 0.4 mile off the SW section of the bay, in a depth of 27m, sand.

      Higashisaki Wan is an open bay penetrating 0.5 mile to the W on the S side of Higashi Saki; the general depths in the bay are from 20 to 40m. The coast from Higashi Saki to Minami Saki, 3.25 miles SSW, consists of steep cliffs with no landing areas.

      Oki Minato (Oki Ko), situated on the SW coast of Haha Shima, lies between Minami Saki and Samega Saki, 2 miles NNW. The bay is open to the W, but is protected against winds and waves from the SW.

      Oki Minato is divided into two harbors. The inner harbor is situated between Samega Saki and Oki Misaki, 0.5 mile SE. Okimura Asane extends 0.45 mile WSW from Oki Misaki and blocks the entrance to the inner harbor. The inner harbor is shoal but a channel that leads to Okimura was being dredged to a depth of 4.5m. A directional light on Oki Misaki marks the fairway to avoid Okimura Asane.

      Large vessels may anchor temporarily in Oki Minato with Maru Shima bearing 171° and Kita Ne, close off the N end of Muko Shima bearing 254°, in a depth of 18.3m, sand. The anchorage is calm in NE winds; however, in SE to NW winds, swells enter and cause a vessel to drag.

      From Samega Saki to Inui Saki, 5 miles NNW there are several indentations in the coast, but none provide protection. Megane Iwa, 1 mile NW of Samega Saki, and Sawara Ne, 1 mile SW of Inui Saki, are two of the many rocks and islets that are charted off the W coast of Haha Shima.

      Hira Shima is located 1.5 miles SSW of the S extremity of Haha Shima. There are several islets and straits charted between these two islands; these straits are narrow, with many rocks and reefs and are only navigable by small craft.

      4.20 Muko Shima (26°36'N., 142°08'E.) is located 1 mile NW of Hira Shima; it is a wooded island mostly bordered by steep cliffs, and on its E and W sides there are occasional beaches of sand and rock.

      Ane Shima is located 1 mile S of Hira Shima. A chain of mountains run from the N to the S along the E and W coasts. The periphery of the island consists of steep cliffs and there is no place to land. Dobu Iso, which uncovers 0.3m, lies 0.85 mile ESE of the S extremity of the island.

      Aneshima Seto, between the islands Ane Shima and Hira Shima, is about 0.28 mile wide between the 20m curves. Passage through this channel is difficult for small vessels because of strong tidal currents.

      Imoto Shima (26°33'N., 142°12'E.) about 2.25 miles E of Ane Shima, is densely covered with trees. The coast consists of rocks and steep cliffs, but landings can be made on the W coast.

      Mei Shima about 0.5 mile ENE of Imoto Shima is ringed by steep cliffs, but small boats can reach the beach on the W side.

      Sukezo Asane, two detached rocks, lie 0.25 mile off the S coast; the sea frequently breaks over them.

      Caution. — The approach to the islands of this group and the

passages between the islands are encumbered with reefs, rocks and islets, whose positions may be seen on the charts.

Kazan Retto

      4.21 Kazan Retto (24°52'N., 141°20'E.), also known as the Volcano Islands and Io Retto, extend along a line about 70 miles long from N to S. Kita-Io Shima, the farthest N of the group, lies 85 miles SSW of Haha Shima. There are three islands comprising the group; from N to S they are Kita-Io Shima, Io To (Io Shima), and Minami-Io Shima.

      These islands are of volcanic origin, and gas continues to escape from them, especially on Io To, and from the sea that surrounds them. It has been reported (1992) that sulpherous smoke has been erupting from the sea about 55 miles SSE of Minami Io Shima in the vicinity of Minami Hiyosi Seamount.

      Kita-Io Shima (25°26'N., 141°17'E.) contains a chain of mountain peaks running N to S through its middle. Sakakiga Mine, the highest peak, 804m high, is located in the S part of the island. The coast is precipitous cliffs except for sections on the E and W coasts. The 20m curve lies about 0.2 mile offshore and the 200m curve lies from 0.75 mile to 1.25 miles offshore.

      Maguro Asane, with a depth of 14.6m and Funka Asane, with a depth of 13.7m, lie 0.6 mile WSW and 2.5 miles WNW, respectively, from the island’s N extremity.

      Kaitoku Kaizan (Kaitoku Seamount), a submarine volcano, lies approximately 48 miles NNW of Kita-Io Shima. In 1984, a bank with a depth of 10m, was reported in position 26°11.5'N, 141°00.9'E, about 6 miles NW of Kaitoku Kaizan.

      Winds — Weather. — During the spring and summer, the SW winds are dominant; NE winds prevail during autumn, and W winds prevail in January and February. There is considerable rain from April to June, and frequent fogs. Strong winds often blow from August to October, and the sea is fairly calm in June and July.

      Tides — Currents. — The flood current flows NW and strikes the SE end of the island. Part of the flood flows N along the E coast while the other part flows W at 1 knot S of the island. At the N extremity of the island, the flood current that flows along the E coast joins a current from the W and makes an E current, whose velocity reaches 1.8 knots. Between Funka Asane and the island, flood currents set NNW at a maximum velocity of 1.5 knots; ebb currents set SSE at a maximum velocity of 1 knot. Off the N coast of Kita-Io Shima, the ebb current flows E at a rate of 1.75 knots. Elsewhere on the ebb tide the directions are reversed and the velocity increased by 50 per cent.

      Anchorage. — Kita-Io Shima has no good anchorage, but an unprotected berth can be obtained 0.4 mile SE of the village Ishino, on the E side of the island.

      The inter-island steamer usually anchors, in 24m, with warehouses on the shore bearing 276° and the SE extremity of the island bearing 200°. The rocky holding ground is poor.

      4.22 Io To (Io Jima)(Io Shima) (24°47'N., 141°19'E.) is located at the mid-point of Kazan Retto, about 36 miles S of Kita-Io Shima. The island, which is about 4.5 miles long in a NE to SW direction, consists of two volcanoes, Moto Yama in the NE and Suribachi Yama at the SW end with a narrow strip of land, Chidoriga Hara, between them.

      Moto Yama, 112m high, is a domed hill with a flat peak located near the airstrip. Steam and sulfur gas, visible from offshore, escape from the fissures, or vents, in the hill.

      An aeronautical light is located near the airstrip.

      Chidoriga Hara is a volcanic dune, with sandy beaches at its E and W ends.

      Suribachi Yama (Mount Suribachi), 161m high, a dormant volcano in the form of a truncated cone, rises at the SW end of the island.

      Io Shima is reported to be radar conspicuous at 17 miles.

      Tides — Currents. — North of Kitano Hana, the N extremity of the island, the ebb current sets E at 1.5 knots; SW of Tobiishi Hana, the S extremity of the island, the flood tide sets NW at 1.75 knots; W of Kama Iwa the flood current sets SW at 1.3 knots; and NW of Kangoku Iwa the flood current sets W at 2.5 knots.

      Anchorages. — Anchorage can be obtained about 2.8 miles NE of Tobiishi Hana, close S of a line connecting Suribachi Yama and Higashi Iwa, off the village of Minami. The depth at the anchorage is 12m, sand, good holding ground.

      Caution. — Higashi Iwa are a group of uncovered rocks, 6m high, located about 2 miles E of the E extremity of Iwo Shima. Kama Iwa lies 0.55 mile off the W coast and Kangoku Iwa, 8.2m high, lies 0.75 miles N of Kama Iwa. There are two rocks located on the shoal area 0.35 mile W of Kangoku Iwa that uncover at LW.

      There are numerous wrecks on the W coast of Io Shima, N of Tobiishi Hana and close off the beach, as indicated on the chart.

      Due to volcanic action, the contour of the shoreline and the depths in the approach to Io Shima are constantly changing. Great care should be exercised when approaching or anchoring in these waters.

      4.23 Minami-Io Shima (24°14'N., 141°28'E.) is a volcanic island located 33 miles SSE of Io Shima. The island is about 1 mile long in a N to S direction and has a height of 918m; this peak is often covered by fog and clouds. The island is bordered by cliffs and rocky beaches. The 20m curve lies from 0.1 mile off the W coast to 0.6 mile off the E coast.

      In 1974, an islet was reported to lie 1.75 miles NE of the NE extremity of the island. In 1982, discolored water was observed in the vicinity of position 24°16.6'N, 141°29.2'E. In 2005, discolored water, with submarine volcanic activity, was observed in position 24°17.4'N, 141°29.1'E.

      Fukutuku-Okano-Ba, a submarine volcano, lies 2.5 miles NE of Minami-Io Shima, and a reef, with a depth of 18.3m, lies 0.5 mile farther NW. In 1904 and in 1914, an island was reported in this area, which has subsequently subsided below the surface. In 1986, the volcano erupted and an islet was formed, but three months later the islet had disappeared, leaving a least depth of about 1m in the area.

      Kita-Hukutoku Tai, a submarine volcano, lies about 11 miles NNW of Minami-Io Shima.

      Discolored water and a suspected volcanic eruption were reported (1987) in the vicinity of Fukutuku-Okano-Ba. An additional account of discolored water was reported in this position in 2006.

      Caution is necessary when navigating in this area.

United States. National Geospatial-Intelligence Agency.
      Sailing Directions Japan (Enroute).
Eighteenth edition.
Volume I.
Pub. No. 158.
Springfield, Virginia, 2022.
pp. 98-101.

Bonin Islands  Source  Whalesite