The Miocene Ushikiri Formation, a 14 Ma submarine slope deposit, contains sediment gravity flow and slide deposits. Some submarine slides may have been triggered by turbidity currents.

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This paper discusses effects of methane hydrate (MH) formation and dissociation on water content of the sediment in the eastern Nankai Trough area. Sediment can be divided into three types. The Type 1 sediments indicate coarser than 20μm in median with inverse and normal grading structures, and the Type 2 sediments are finer than 20μm in median with normal grading structure. Both sediments are interpreted as turbidite deposits. The Type 3 sediments show constant grain size, almost 10μm in median, and this fact implies this type is of hemipelagic mud. As to the Type 1 sediments after MH dissociation, relationship between water content below 10% and clay-slit-sand contents differs from that in water saturated sediments. This fact implies that MH accumulated in the sediments with water contents below 10%, and dehydrating action occurred during dissociation of MH. In this study, water content decreased at most 15% after MH dissociation. Low water content sediments owing to selective dehydration can provide one of the criteria for identifying the MH-bearing strata in past times.

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In order to complement regional data of modern tsunami deposits formed in various coastal environments, we described in detail thickness, grain size and sedimentary structures of the deposit formed by the 2011 Tohoku-oki tsunami at some areas in Ibaraki and Chiba prefectures, Japan. We also discussed effects of the tsunami size on the characteristics of tsunami deposits, comparing them to some tsunami deposits formed in other areas.
Although the thickness of the tsunami deposit was influenced by local topography, it showed the thinning trend towards the inland distribution limit in all transects. Taking into account the results of previous studies tsunami deposits often show inland thinning toward the distribution limit regardless of tsunami sizes and grain size of source sediments. The thicknesses of the tsunami deposits near the shore were more variable than the deposits left inland. This may have resulted from complex tsunami behavior due to existence of protection forest and other artificial materials around the shore.
On the other hand, the inland grain-size fining trend was unclear in all transects. Our data indicate that not all tsunami deposits show this trend. Even if a deposit in geologic stratum does not show an inland grain-size finning trend, the possibility that it might have formed by paleotsunami cannot be completely denied.

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The purpose of this research is to investigate a possibility of a small plain flume as teaching material for a meandering-river channel change. In the experiments, the first meandering stream was changed into an anastomosing stream along with increase in water discharge, slope gradient and sediment supply. The channel change was characterized by a meander-bend evolution and avulsion. The braiding channel occurred at the riffle, which was shallower point by deposition in a channel. This research will be continued to investigate the possibility of comparing a result of an experiment with an actual river.

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