Large rivers with high sediment discharge, such as the Amazon, Ganges-Brahmaputra, and Huanghe (Yellow) rivers, have formed mega-deltas at their mouths. This paper reviews morphology and sediments of mega-deltas and their Holocene evolution in relation to sea-level changes, channel avulsion, and past-sediment discharge. Application of various radiometric dating techniques to delta deposits, especially since the 1980's has made it possible to clarify delta evolution dynamically on 10-to 1000-year time scales. Most of the deltas are located in developing countries, and have environmental problems principally caused by human activities. For the evaluation of current status and human activities in deltas and drainage basins, both natural and anthropogenic changes of deltas should be analyzed from the viewpoints of geology, sedimentology, and their evolution.
The Rokko Mountains are mainly composed of three rock units : Nunobiki granodiorite, Rokko granite, and Dobashi quartz diorite. Alteration of these rocks is examined by XRD analysis and magnetic susceptibility meter. All granite rocks are divided into four categories of alteration : unaltered (A), unaltered (B), weathered, and hydrothermally altered. Unaltered (A) rocks do not contain any secondary minerals and indicate high magnetic susceptibilities (MS), which are probably near the original ones (n × 10-3 SI unit). Unaltered (B) rocks also do not contain secondary minerals, but their MS is clearly low. These rocks are typically distributed in crushed zones along the main faults that enclose and cut the Rokko Mountains. Weathered rocks are defined by the presence of kaolin. Their MS are very low (n × 10-5 SI unit). Highly weathered rocks are preserved at the northern part of the backbone of mountains, while they are heavily eroded at the southern part. Six groups of hydrothermally altered rock are defined by the presence of characteristic minerals such as mordenite, calcium zeolites, sericite, chlorite-smectite series, kaolinite, and calcite. Hydrothermally altered rocks indicate comparatively low MS (n × 10-4-10-5 SI unit). Most hydrothermal alteration occurred along or parallel to main faults, especially Shabayama, Yusodani, and Arima faults at northern part and Nunobiki and Suwayama faults at southern part.
The significance of health condition, disease, and causes of death as social indicators has been pointed out in the social sciences. Here, this is discussed in terms of the modernization era of Europe, in which relations between health condition of inhabitants and social development became evident. From a geographical viewpoint regional variations of diseases have been investigated to describe the regional context. The author analyzes disease as a cause of death covering the period from the second half of the 19th century to the beginning of the 20th century in Europe, using data on cause of death as documented in church registers of three villages in the province of South Tyrol, northern Italy : Salurn, Kastelruth, and Unserfrau in Schnals. For this purpose causes of death are classified into 8 categories by affected organ and 16 categories by disease within two periods : the first from 1870 to 1880 and the second from 1900 to 1910. Patterns of causes of death and their changes are compared among the villages. Within these periods, as a whole, the transition pattern of cause of death showed a change from inflammatory diseases such as gastroenteritis to tuberculosis to chronic diseases such as cancer and cerebrovascular diseases. This process has been observed particularly in villages where regional changes such as urbanization and modernization took place earlier. On the other hand, processes of change in each village were diverse. In villages innovated through urbanization and tourism, such as Salurn and Kastelruth, the trend of causes of death occurred earlier, while in geographically isolated villages such as Unserfrau in Schnals, a slower change in the causes of death is observed. Such a relation between disease as cause of death and regional changes can be explained by the theory of “sequent occupance, ” advocated by the American geographer D.S. Whittlesey, for the purpose of explaining land use in northern New England. According to this theory, changes of regional land use reflect the various stages of regional change : land use depends greatly on specific regional elements. A particular disease as cause of death, predominating in a given region, results from the interaction of regional elements. The trend of disease in a region is shown to follow regional changes.
Well-defined Holocene marine terraces are present continuously along the west coast of the Asahi Mountains. This area faces the Sea of Japan and is located east of the epicenter of the 1964 Niigata earthquake, which caused an uplift with considerable westward tilting of Awashima Island, located west of the epicenter. In contrast, the study area subsided at the time of the destructive 1964 earthquake, although the presence of Holocene and stage 5e or other marine terraces record the long-term uplift during the late Quaternary of this area (Ota, 1971). This paper describes the nature and the age of Holocene terraces, which had not been studied in detail, and discusses the uplift pattern and its tectonic significance. The Holocene marine terrace here is usually wave-cut platform with few beach deposits. At large river mouths, however, there are relatively wide and flat valley bottom plains, burying drowned valleys, and separated by sand dunes from the present beach. Radiocarbon age from the bottom of terrestrial deposits on marine deposits is 6.4 ka or slightly younger, and indicates that the emergence of Holocene terrace took place ca. 6 ka. The former shoreline height of the Holocene terrace ranges from 8 m to 4 m. Thus, the maximum uplift rate reaches 1.3 m/ka, which is larger than the uplift rate deduced from the Ml (stage 5e) terrace. The Holocene terrace is subdivided into two on the southern part of the Budo Mountains, where the uplift rate of Ml terrace is the maximum. The late Quaternary uplift of this area, deduced from marine terraces, is discordant with coseismic subsidence caused by the 1964 Niigata earthquake. This means that the uplift of this study area is not caused by seismogenetic fault for the 1964 earthquake. We cannot find the specific onshore active fault within or at both sides of the Budo Mountains and the Maya Mountains that was responsible for the coastal uplift. To interpret such a long-term uplift of the coastal area, we need to assume that offshore reverse active fault dipping eastward is repeatedly activated. Establishing the exact location, nature, and length of offshore faults is important to interpret the coastal uplift of this area.