The temporal and spatial change in characteristics of wind and wave generated by Typhoon 9119 in Seto Inland Sea is analysed by using the wind and wave prediction models. High waves which attacked the coast of Yamaguchi Prefecture were generated over the outer ocean and invaded through Bungo Strait, growing owing to local gale winds. After the passage of the typhoon, westerly gale winds occurred over the Inland Sea. Associated with these winds, waves suddenly developed and a high wave area initially formed around Hoh-yo Islands. Then, the high wave area moved toward the east and attacked the coast of Ehime Prefecture. These gale winds and high waves caused severe disasters along the coast of the Inland Sea. One of the main causes of the disasters is that the gale winds in the typhoon area are amplified by the local topographic effect, and high waves and storm surges are also amplified by the gale winds. It is also pointed out that salt harm occurred because of gale winds, high waves and small rainfall.

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Megascopically, nodules are composed of nuclei and concentric shell layers. The hard surface of nuclei is necessary for the start of nodule formation. The concentric shell layers are formed by cyclic embedding of nodules in the sediment. During their embedding, 10 Å manganates are precipitated diagenetically from interstitial water, which are rich in manganese. During their exposure in bottom water, vernadite is formed hydrogenetically, of which concentration of manganese is almost equal to that of iron. Microscopically, concentric shell layers have a zonal structure which is classified as columnar, laminated, mottled, massive and compact. The columnar and mottled zones are the most abundant, and the former is observed in the nodules of hydrogenetic origin and the latter is in those of diagenetic origin. The zonal structure is considered to be formed as follows. When manganese oxides are precipitated, the pH in the micro-environment is lowered and further oxidation of Mn²⁺ is inhibited. During the low pH, hydrated iron oxides and silica are precipitated. After restoration of the initial pH, manganese oxides can again precipitate. Whether ferromanganese concretions are of biological origin or of physicochemical origin is the crux of the problem. Further, there has been a debate on the origin of nodules between procaryotic (bacterial) and eucaryotic (foraminiferal) stromatolites. Although sessile benthic organisms such as foraminifera may prevent cracking of nodules and sediment feeders may move nodules, the direct involvement of these organisms in the growth of nodules is questionable. On the other hand, manganese oxidizing bacteria may contribute to the growth of nodules.

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