Geochemical data on the evolution of seawater chemistry during the past one billion years (Sr/Ca, Li/Ca, Ge/Si, 187 Os/186 Os, δ34 S, 87Sr/86 Sr) were summarized. These data indicate that the variations in seawater chemistry have been influenced by the circulation of ydrothermal solution at mid-oceanic ridges. The circulation rate of hydrothermal solution is related to ocean floor spreading rate. Thus, it is considered that tectonics is important factor in controlling the chemical evolution of seawater. Tectonics affects not only seawater chemistry, but also CO 2 content in atmosphere and consequently climate. A correlation between δ34 S and 87 Sr/86 Sr variations of seawater indicates that hydrothermal solution and seawater-rock interaction was important for causing the variations in seawater chemistry before 1 billion years ago. Geochemical data (REE etc.) on BIF (banded iron formations) and sedimentary rocks indicate that the hydrothermal solution-oceanic crust interaction controlled Archean seawater chemistry. Influence of this interaction on the seawater chemistry decreased from Archean to Proterozoic, while weathering and biogenic activity became important.
Many distinct lineaments have been recognized by Landsat images in Korean Peninsula. The Yangsan fault system situated in the southeastern part of Korea is especially linear, continuously traceable for a long distance (about 200km), and particularly remarkable among these lineaments. The topographic expression of the Yangsan fault system is derived from the straightly stretching fault valley with wide shattered zones in the direction of NNE-SSW. This fault system extends for about 200km from the mouth of the Nagdong River west of Busan in the south to Yeondong in the north, and geologically separates Korean Peninsula from the Japan Sea. The amount of horizontal displacement may reach 30km. It is recognized as one of the most important faults in Korean Peninsula. From the interpretations of aerial photographs, and field surveys along the central part of the Yangsan fault system, the main results are summarized as follows: 1. The Yangsan fault system has repeatedly moved in the late Quaternary. The lower to higher river terrace surfaces on this system show cumulative vertical offsets. 2. The vertical component is upthrown on the east side from considering the terrace offset and the distribution of the mountainous lands. This vertical movement is reverse to the topographical situation on the meso-scale. 3. The fault trace is extremely straight. The fault plane is almost vertical. The shatteredzone exceeds tens of meters in width with a remarkable fault gouge. 4. The longer axis of flat clasts within the gravel observed in excavated the exploratory trench showed the re-arrangement along the fault. The predominantly right-lateral movements were recognized as the elongation of clayey parts and breccias in the fault gouge. 5. From these characteristics, the Yangsan fault was clarified to be active with predominantly right-lateral movement. Estimated ages of terraces and its deposits give average rates of vertical and right slip on the Yangsan fault system at about 0.02-0.03mm/y, and at least 0.05-0.1mm/y, respectively. 6. The fault topography is not found on the lower and lowest terraces. As the surface of the terrace has widely been cultivated as paddy fields for long historical time, lower fault scarplets less than a few meters high might have been modified or destroyed by the human actions. Therefore, we cannot mention the existence of the younger movement on the lower and lowest terraces.
Many spike-like anomalies of grain densities and clay mineral concentrations in silty sediments have been recognized in the uppermost part (60cm in length) of a piston core, named SG2, in Lake Suigetsu of Mikata area, Fukui Prefecture, central Japan. Grain density spikes indicate large precipitations of iron sulfides and carbonates from interstitial waters in the upper part of muddy turbidites, which were suddenly caused by earthquakes. Spikes of Fe- and Mgrich chlorite/illite ratio indicate large accumulations of detrital clay particles which flowed into lake by sudden flood. After the Urami Canal was constructed between Lake Suigetsu and Lake Kukushi, which connects both lakes directly to the Sea of Japan, in 1664 A. D., sea water began to enter Lake Suigetsu and the lake changed its water conditions from fresh-to brackish-water. Iron mineral concentrations changed from siderite (FeCO3) to pyrite (FeS2) which was formed under sulfate reduction condition, in 35cm depth of a core column. Core column from 29cm to 35cm in depth shows a silty layer. Macroscopic observations and historical informations presumed a silty layer to be a muddy turbidite which was probably formed by Kanbun Earthquake (June 6, 1662 A. D.). This interpretation suggests that 29cm depth of core column represents deposition surface in 1662 A. D. Based on relative spacing between 0cm (=1991 A. D.) and 29cm (=1662 A. D.) depths, formation ages of grain density and chlorite/illite ratio spikes can be dated. Grain density spikes are interpreted to represent historical earthquake events of 1449, 1532, 1586, 1605 (Keicho Earthquake), 1662, 1683, 1707 (Houei Earthquake), 1819, 1854 (Ansei Earthquake), 1891 (Nou-bi Earthquake), 1909 (Gonou Earthquake) and 1963 (Echizenmisakioki Earthquake) of the Wakasa region. Chlorite/Mite ratio spikes are interpreted to represent historical flood events of 1633, 1691, 1701, 1729, 1735, 1786, 1791, 1825, 1842, 1853, 1866, 1895, 1953 (Typhoon No.13), 1959 (Isewan Typhoon), 1965 (Typhoon No.23 and No.24) in the Wakasa region. Five spikes cannot be correlated to historical earthquakes and floods. These events that represent depositions in 1646, 1799, 1848, 1931 and 1936 are probably correlated with historical engineering works of 1642, 1801, 1848, 1932 and 1934-35 around Lake Suigetsu. All events suggest that non-bioturbated fine-graind sediments of meromictic lake near human communities recorded any earthquakes, floods and human activities over a long periods of which no historical literature exists.
The maximum glacial extent and depression of equilibrium line altitudes (ELAs) in the Hiunchuli massif of West Nepal were reconstructed by air photograph interpretation. The present glaciers are characterized by either of the following two types: steep valley or valley sided type. On the other hand former glaciers were large plateau glaciers with many radial outlets. During the maximum glacial extent, the lowest ELA lay at an altitude of 4, 100m, about 1, 000m below the present ELA and the area of the maximum glacial extent was 200 km2, some 200 times as large as the present one.
Niigata-Yakeyama volcano, situated in the northernmost part of Central Japan, is a small dome-shaped stratovolcano, and has many records of its eruption. The geology of this volcano has been already described in detail by the auther. In this paper, more detailed volcanic history of Yakeyama is compiled mainly on the basis of nine 14C ages of the ejecta newly determained and the stratigraphic relationship between the ejecta and the archaeological remains. The results are summerized as follows:(1) The first volcanic activity of Yakeyama started ca. 3, 000 years ago.(2) During historic times, three violent magmatic eruptions took place ca. 1, 000 years ago, and in 1361 and 1773 and produced pyroclastic surges, pyroclastic flows, and lava flows.(3) After the 1773 magmatic eruptions, Yakeyama repeated a series of steam explosions respectively in the mid-nineteenth and late-twentieth centuries.