| 西之島周辺の海底地形（1992年測量）。西之島南東に凹地があり、直径2km程度の火口地形の中心と考えられ、旧島（西之島西半分）は火口縁にあたる。５万分の１沿岸の海の基本図「西之島」（海上保安庁水路部、1993）より作成。 |
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| Bathymetric map around Nishino-shima (surveyed in 1992) based on Basic Map of the Sea (1:50,000) "Nishino-shima" (Japan Coast Guard, 1993) showing ca. 2 km diameter depression (presumably a crater) at the southeast of Nishino-shima. Older island (western half of Nishino-shima Island) is part of crater rim. | |||