著者
湯田 ミノリ 伊藤 悟 内田 均 木津 吉永 伊東 純也
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.117, no.2, pp.341-353, 2008-04-25
参考文献数
21
被引用文献数
2 1

The use of GIS in education in Japan has not yet been widely diffused, although the computer and network environments of schools have been improved, and teachers have already recognized the characteristics and advantages of this tool in education.<br> Nowadays, GIS has been intergraded into many aspects of our lives. Mobile phones are also basic tools in our daily lives. A GIS application that runs on cellular phones would be helpful in school education.<br> From this point of view, the authors have developed a system called Cellular Phone GIS including a GIS application for mobile phone (hereinafter Cell Phone GIS Application) and its web-based GIS viewer application for PC using Google maps (hereinafter PC viewer), and carried out fieldwork at an upper secondary school using these tools. Data can be input and edited outdoors with the Cell Phone GIS Application. These data can be viewed on both cellular phones and personal computers via the Internet. Students carried out a land use survey in the area around the school with the Cell Phone GIS Application, and examined and presented the results using the PC viewer in class.<br> Students participated actively in the fieldwork with the cellular phone. Through experience of the survey with the tool, they found many new things and learned to adopt multi-dimensional points of view and ways of thinking. Also, this project generated more interest among students in geography classes.<br> The Cell Phone GIS Application provided high school students with a feeling of accomplishment from the fieldwork. Meanwhile, this tool and PC viewer minimized work after fieldwork because users do not have to input and aggregate data again. Therefore, teachers and students can use course hours efficiently. The Cellular Phone GIS can provide an environment in which students are able to receive educational effects from fieldwork.
著者
都司 嘉宣
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.106, no.4, pp.486-502, 1997-08-25
参考文献数
12
被引用文献数
2 2

A field survey of the damage of the Amami-Oshima-Kinkai earthquake (<I>M</I><SUB>w</SUB> 7.1) and its tsunami of October 18, 1995 was conducted for four days from the next day of the main shock. A large aftershock (<I>M</I><SUB>w</SUB> 6.8) occurred in the next day and was also accompanied with a small tsunami. We conducted interviews of the inhabitants, and measured heights of the both tsunamis. The maximum height of the tsunami of the main shock was 3.0 m at Urahara Port on the south coast of Kikai-jima. Earthquake damage mainly occurred on Kikai-jima, where stone walls were fallen down at 91 places, the water supply facility of the island was disordered, and several concrete slabs slid down at Wan Port. Several fishing boats were wrecked due to the both tsunamis at ports on Kikai-jima and Amami-Oshima. Imamura-Hatori's magnitudes of the main shock and the large aftershock are <I>m</I>=1.0 and <I>m</I>=0.0, respectively. Abe's magnitude of the tsunamis the main shock is estimated to be <I>M</I><SUB>t</SUB>=7.6 and is large for the earthquake magnitude. A gigantic earthquake (<I>M</I>8.0) with a larger tsunami occurred on June 15, 1911 in the sea region close to the present event, and its folktale is handed down by the inhabitants of Kikai-jima.
著者
漆原 和子 鹿島 愛彦 榎本 浩之 庫本 正 フランツ ディーター ミオトケ 仲程 正 比嘉 正弘
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.108, no.1, pp.45-58, 1999
参考文献数
38
被引用文献数
2 3

Observations of the solution rate of limestone tablets from 1993 to 1997 have been utilized to clarify the degree of karstification from northern to southern Japan.<BR>Limestone tablets were placed at seven observation points stretching from northern to southern Japan : Toma, Abukuma, Chichibu, Akiyoshidai, Shikoku Onogahara, Ryugado, and Minamidaito. Three groups of four limestone tablets from Slovenia, Guilin (China), Chichibu, and the fourth tablet from limestone indigenous to the obsevation point, were arranged on three levels at each observation point : 1.5m above the ground, the A3 horizon, and the B<SUB>2</SUB> horizon. Measurements were taken of the solution rates of the tablets at each observation point from 1993 to 1997. Thornthwaite's method was used for calculating water balance to ascertain the relation between solution rate and water balance factors. The solution rates of limestone tablets placed 1.5m above the ground show a high correlation coefficient between (water surplus (WS) minus water deficit (WD)). On the other hand, limestone tablets planted in the soil had a solution rate from two to three times higher than those suspended in the air. The solution rates of limestone tablets located in the A<SUB>3</SUB> and B<SUB>2</SUB> horizons exhibited the highest annual precipitation correlation coefficient. The high CO<SUB>2</SUB>values under warm, humid conditions may account for the higher solution rates of the tablets planted in the soil.<BR>The solution rate tendency curve achieved its greatest range during the five years in direct proportion to the WS-WD ratio in 1993, when a cool, humid summer prevailed throughout most of Japan. The solution rate tendency curve marked its smallest range during the five years in proportion to the WS-WD ratio at all locations for limestone tablets suspended in air in 1994, under conditions of an extremely hot and dry summer, such as occurs only once in a hundred years. In general, however, the solution rates of the limestone tablets were high when the WS-WD ratio ranged between 1, 000 to 1, 600mm. Within this range, the solution rates at each observation point decreased slightly as the WS-WD ratio decreased.
著者
菊地 正幸 山中 佳子 纐纈 一起
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.110, no.2, pp.204-216, 2001
参考文献数
12
被引用文献数
1 16

A sudden collapse of the summit of Miyake-jima occurred on July 8, 2000, together with intermittent eruptions. This collapse generated long-period seismic waves with a dominant period of about 10s. Following this event, very long-period seismic pulses (VLP pulses) with a duration of about 50s were observed a few times a day until they ceased at the largest summit eruption on August 18. We analyzed these seismic pulses using waveform data recorded at several domestic stations for broadband seismographs and strong motion seismometers on Miyake-jima. The July 8 event is well characterized by a single-force directed initially upward and later downward during 12 sec. The single-force is interpreted as an abrupt collapse of massive rock. The total mass is estimated to be about 5 × 10<SUP>10</SUP> kg with fall of about 300 m. On the other hand, VLP pulses are modeled by moment-tensors with an isotropic component. They are located about 1 km southwest from the summit and 2 to 3 km deep. All three principal values are positive. The largest one is horizontal and the smallest one is near vertical. The total volume change due to 39 VLP pulses is 2.6× 10<SUP>8</SUP>m<SUP>3</SUP>, amounting to nearly one half of the total volume of the summit collapse. Based on theresults, we propose a buried geyser model. A large reservoir of hot water was formed just after the summit collapse on July 8. The ground water poured into the reservoir, being rapidly heated by hot rock underneath, and evaporated to form a highly pressurized steam, which pushed a lower conduit piston into the magma reservoir to generate VLP pulses. Non-isotropic expansion of the VLP pulses may be ascribed to the shape of the magma reservoir.
著者
石原 舜三
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.117, no.3, pp.674-677, 2008-06-25
参考文献数
15

Worldwide, HREEs are not abundant, but LREEs are. HREEs are limited to certain weathered crust deposits in China where the original granites are rich in HREEs and surface weathering is intense. Because of environmental limitations on mining, it is necessary to discover the primary sources of REEs in alkaline igneous rock provinces. Indium can be recycled easily, and primary sources can be found in Sn-Zn-sulfides deposits of both volcanic and subvolcanic settings. Tungsten and bismuth are also limited mineral resources, but can be found in carbonate rocks with fractionated ilmenite-series granite intrusions. Molybdenum can be supplied sufficiently from porphyry-type deposits.
著者
長沼 毅
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.112, no.2, pp.226-233, 2003-04-25
参考文献数
45
被引用文献数
4 1

The search for life on the edges (frontiers) of the global biosphere bridges earth-bound biology and exobiology. This communication reviews recent microbiological studies on selected "frontiers", <I>i.e</I>., deep-sea, deep subsurface, and Antarctica. Deep-sea is characterized as the aphotic (non-photosynthetic) habitat, and the primary production is mostly due to the chemosynthetic autotrophy at the hydrothermal vents and methane-rich seeps. Formation of the chemosynthesis-dependent animal communities in the deep leads to the idea that such communities may be found in the "ocean" of the Jovian satellite, Europa. An anoxic (no-O<SUB>2</SUB>), as well as aphotic, condition is characteristic of the deep subsurface biosphere. Microorganisms in the deep subsurface biosphere exploit every available oxidant for anaerobic respiration. Sulfate, nitrate, iron (III) and CO<SUB>2</SUB> are the representative oxidants in the deep subsurface. Below the 3000 m-thick glacier on Antarctica, >70 lakes having liquid water are entombed. One of such sub-glacial lakes, Lake Vostok, has been a target of "life in extreme environments" and is about to be drill-penetrated for microbiological studies. These biospheric frontiers will provide new knowledge about the diversity and the potential of life on Earth and facilitate the capability of astrobiologial exploration.
著者
本井 達夫 鬼頭 昭雄 緑川 貴 荒川 理 笹井 義一 陳 永利
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.117, no.6, pp.1015-1028, 2008-12-25
被引用文献数
1 1 1

Climate model experiments are carried out to understand the relationship between large-scale topography and climate variation. Mountain uplift experiments show that sea surface temperature, surface wind fields, precipitation and sea surface salinity are strongly influenced by mountain uplift. An enhanced Asian monsoon due to mountain uplift causes stronger seasonal coastal upwelling in the Indian Ocean and freshening in the Bay of Bengal, Yellow Sea and East China Sea. Mountain uplift experiments using a higher resolution atmospheric general circulation model reveal that the spatial pattern of precipitation becomes finer as resolution increases, and that there is a sharper contrast in the salinity distribution near coastal regions. Experiments in which the Panamanian Gateway is closed, opened and re-closed suggest that reorganization of the ocean current due to closure of the Panamanian Gateway induces a cooler and drier climate with a permanent halocline and sea ice in the subarctic Pacific.
著者
丸山 茂徳 大森 聡一 千秋 博紀 河合 研志 WINDLEY B. F.
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.120, no.1, pp.115-223, 2011-02-25
被引用文献数
5 23

Pacific-type orogeny (PTO) has long been recognized as a contrasting accretionary alternative to continent-continent collisional orogeny. However, since the original concept was proposed, there have many new developments, which make it timely to produce a new re-evaluated model, in which we emphasize the following new aspects. First, substantial growth of Tonarite–Trondhjemite–Granite (TTG) crust, and second the reductive effect of tectonic erosion. The modern analog of a Pacific-type orogen developed through six stages of growth exemplified by specific regions; initial stage 1: the southern end of the Andes; stage 2: exhumation to the mid-crustal level at Indonesia outer arc; stage 3: the Barrovian hydration stage at Kii Peninsula, SW Japan; stage 4: the initial stage of surface exposure of the high-P/T regional metamorphic belt at Olympic Peninsula, south of Seattle, USA; stage 5: exposure of the orogenic core at the surface at the Shimanto metamorphic belt, SW Japan; and stage 6: post-orogenic processes including tectonic erosion at the Mariana and Japan trench and the Nankai trough.<br> The fundamental framework of a Pacific-type orogen is an accretionary complex, which includes limited ocean floor material, much terrigenous trench sediment, plus island arc, oceanic plateau, and intra-oceanic basaltic material from the ocean. The classic concept of a PTO stresses the importance of the addition within accreted rocks of new subduction-generated arcs and TTGs, which were added along the continental margins particularly during the Cretaceous. Besides the above additional or positive aspects of a PTO, here we emphasize the negative effects of previously little-considered tectonic erosion caused by subduction over time. The evaluation of such extensive tectonic erosion leads a prospect of the presence of huge quantities of TTG material in the lower transition zone, where many subducted slabs have ponded, as illustrated by mantle tomography. This is confirmed by density profiles of the mantle, which show that TTGs are abundant only along the bottom of the upper mantle accompanied by slab peridotite, lherzolite, and MORB. The major velocity anomaly in the lower transition zone is best explained by the predominance of SiO<sub>2</sub> phases, hence TTG, and not by MORB or ultramafic rocks. Reasonable calculations indicate that at a depth range of 520-660 km TTG material amounts to 6-7 times more than the total mass of the surface continental crust.<br> The traditional view is that the Japanese islands evolved since 520 Ma through five Pacific-type orogenies, which grew oceanward, thus creating a continuous accretionary complex <i>ca.</i> 400-500 km wide, with TTG growth at the continental side of each orogen. However, the subducting oceanic lithosphere has produced five times more TTG crust compared with the present TTG crust in the Japan islands. This is explained by the fact that over time tectonic erosion has dominated the increasing arc-TTG crust. Accordingly, Japan has lost four arc-TTG crusts to tectonic erosion. TTG material, such as trench sediment, arc crust, and continental margin crust, was fragmented by tectonic erosion and transported into the bottom of the upper mantle at depths of 520-660 km. Worldwide data suggest that tectonic erosion destroyed and fragmented most of the Pacific-type orogens.<br>(View PDF for the rest of the abstract.)
著者
山田 周二
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.110, no.1, pp.79-93, 2001-02-25
被引用文献数
1

This study classified Japanese mountains based on mountain ordering using 1 : 500000 topographic maps, and examined the relationships of relief, relative relief and perimeter fractal dimension for the classified mountains. Mountain order was defined in terms of closed contour lines on the topographic map. A set of closed, concentric contour lines defines a first-order mountain. Higher-order mountains can be defined as a set of closed contour lines that contain lower-order mountains and that have only one closed contour line for each elevation. Relief, relative relief and fractal dimension were measured for ordered mountains using personal computer, and were defined as follows : relief <I>E = H/A</I><SUP>1/2</SUP>, where <I>H</I> and <I>A</I> are the height and area of each ordered mountain, respectively; relative relief <I>R</I>= ∑ <I>h<SUB>i</SUB>/H</I>, where <I>h<SUB>i</SUB></I> is the height of the enclosed, lower-order mountains, and represents the degree of vertical roughness of the ordered mountain; fractal dimension was measured for perimeter contour line by the pixel dilation method, and represents the degree of horizontal roughness of the ordered mountain. Japanese mountains were classified into 74 third order mountains and 11 fourth order mountains. The area of a third order mountain varies from 50 to 4712 km<SUP>2</SUP>, and that of a fourth order mountain is 2498 to 15563 km<SUP>2</SUP>. A significant relationship was found among relief <I>E</I>, relative relief <I>R</I>, and fractal dimension <I>D</I> for the ordered mountains (r=0.91, n=85), and can be defined by the expression : <BR>Log<I>E</I>=-a<I>D</I>-bLog<I>R</I>-c<BR>This relationship shows that Japanese mountains have the following morphological characteristics : a high relief mountain has low vertical and horizontal roughness, and a low relief mountain has high vertical and horizontal roughness. These characteristics suggest that slope angle of Japanese mountains converges within a certain range.
著者
宮縁 育夫
出版者
公益社団法人 東京地学協会
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.125, no.3, pp.421-429, 2016
被引用文献数
6

The Kumamoto earthquake(Mj7.3) on April 16, 2016 triggered numerous landslides in and around Minamiaso Village, which is located at the western part of Aso caldera, southwestern Japan. The landslides were divided into two types:landslides occurring at steep caldera walls and landslides generated on the slopes of post-caldera central cones of Aso Volcano. Several landslides occurred on slopes steeper than 25°at the northwestern to western caldera walls, which comprise pre-Aso volcanic rocks (lavas and pyroclastics). The largest landslide (ca. 300m high, 130-200m wide) occurred on the western caldera wall, damaging National Route 57 and the Hohi line of the Japan Railway. Because a clear rupture surface could not be observed, unstable blocks which had been divided by cracks, were likely to collapse due to the intense earthquake on April 16. At the post-caldera central cones of Aso Volcano, earthquake-induced landslides were generated not only on steep slopes but also on slopes gentler than 10°. They occurred in unconsolidated superficial tephra deposits overlying lavas and agglutinates, and the thickness of the slides usually ranged from 4 to 8 m. The sliding masses traveled long distances (<600m), compared to small differences in elevation. The deposits were composed of tephra blocks of a few meters and there was no evidence that they were transported by water. These facts suggest that some landslides mobilized rapidly into debris avalanches, traveling a few hundred meters. The associated debris avalanche resulted in five casualties and severe damage to houses at the foot of the Takanoobane lava dome. The characteristics of the April 16, 2016 earthquake-induced landslides differ from those of rainfall-induced landslides in July 2012, June 2001, and July 1990 at Aso Volcano, and provide important imformation for preventing or mitigating future landslide disasters in the Aso caldera region.
著者
渡辺 満久 齋藤 勝
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.115, no.6, pp.727-736, 2006-12-25

The eastern margin of Echigo Plain, central Japan, is characterized by NNE-SSW trending active faults. The Anchi fault is made up of two segments : the Anchi-nishi fault and the Anchi-higashi fault. Each fault trace is approximately 2-km long. They may be short subsidiary faults on the hanging wall of the master fault in this region (the Tsukioka fault). Trench investigations across the Anchi fault reveal its rupture history as follows : 1) the Anchi-nishi fault and the Anchi-higashi fault are west-dipping reverse faults; 2) the Anchi-nishi fault shows a vertical offset of 1.3-1.9 m after ca. 30 ka; and, 3) the vertical displacement of 3.5 m is associated with two faulting events along the Anchi-higashi fault, one between ca. 30 and 60 ka and the other younger than ca. 30 ka. Geomorphic features indicate that a reverse fault branches into these two faults at a certain depth. Thus, the total vertical offset for the last ca. 30 ky is between 3.1 to 3.7 m. This value is one third of that along the master active fault. If the source fault consists of these active faults, we should evaluate the activity of the master fault taking account of the activity of the Anchi fault. It is very important to know the nature of subsidiary faults, even if they display very short traces.
著者
松本 至巨 尾方 隆幸 内川 啓
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.115, no.2, pp.221-235, 2006-04-25
被引用文献数
1 1

The Northern Japanese Alps (Chubusangaku National Park) has experienced a dramatic increase in the number of visitors since the boom referred to as "the Japanese hundred mountains". The Ushiro-Tateyama Range, located in the northernmost area of the Japanese Alps, provides various alpine landscapes such as cirques, asymmetrical ridges, patterned ground, perennial snow patches and alpine plant communities. Data from 6922 trekkers indicate that the distribution of mountain huts and accessibility to trails control their trekking courses, and that the trekkers concentrate in three mountain areas : Shirouma-mountain area, Goryu-mountain area and Kashima-mountain area. These areas are divided by a landform called kiretto, where a col with steep rockwalls lies along a main ridge, operating as a natural obstacle. Such a concentration suggests that human impacts on mountain geoecosystem occur locally, but intensively.
著者
小野 有五
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.121, no.2, pp.187-214, 2012-04-25
被引用文献数
1 2

Fifty years of studies on glacial landforms in Japan between 1960 and 2010 are reviewed from the personal perspective of a researcher who devoted a major part of his life to these studies. The 1960s was a period in which there was a paradigm shift in the history of glacial landform studies in Japan. This resulted from a series of studies by Tomoya Iozawa using aerial photograph interpretation. He was the first researcher to observe and identify all of the glacial landforms in Japan using aerial photographs, and divided them into two groups: the older and more widespread (Yokoo Stage) and the younger and much less widespread (Karasawa Stage). Following his methodology and staging, extensive research was done in the 1970s, and tephrochronological studies revealed that the older and younger stages correspond to MIS 4 and 2 respectively, although MIS 3 glaciation was recognized later in the Hidaka Range, Hokkaido. A researchers union of glacial and periglacial landforms called <i>Kanrei-chikei Danwakai</i> was established in 1972, Proposed and organized by Isozawa and other young students including the author, it stimulated research. In the 1980s, a reconstruction of the mass balance and flows of past glaciers from glacial landforms was attempted by the author and other researchers. This led to the estimation of the Equilibrium Line Altitude (ELA) of former glaciers in Japan. Inventory work and monitoring of perennial snow patches in the Japanese Alps were also begun in the 1980s, and they encouraged studies on the transformation from perennial snow patch to glacier. In addition, the discovery of an ice body at the bottom of Kuranosuke Cirque, Mt. Tateyama, Northern Japanese Alps gave an important hint to estimating the present (topographical) snowline altitude, which could be much lower than the former evaluation determined only from free air temperature. Both the study of perennial snow patches and mapping of the former ELA clarified the importance of precipitation when determining snowline altitude, and the present ELA was estimated at 2970 m just below the peak of Mt. Tateyama (3003 m). Since the 1990s, glacial landform studies became more closely related to global climatic change within the framework of IGBP-PAGES. Glacial fluctuations in Japan in the last glacial period were mainly controlled by monsoon changes and migration of westerlies, which caused a southern migration of the polar frontal zone. Although the glaciers in Japan were small, even in the glacial period, it is now believed that they are an important indicator of climatic changes because they are very sensitive to monsoon and westerly changes.
著者
磯崎 行雄 丸山 茂徳
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.100, no.5, pp.697-761, 1991
被引用文献数
77 152

The Japanese Islands consist fundamentally of late Paleozoic to Cenozoic accretionary complexes that formed in situ in a subduction zone along the East Asian continental margin, i.e. 2.0 Ga Yangtze craton (South China) and 450 Ma fore-arc ophiolite. Recent research utilizing microfossil and radiometric dating has distinguished several major accretionary complexes, including high-P/T metamorphosed parts, and subordinate ophiolites. In particular, recognition of oceanic plate stratigraphy and age of subduction-related metamorphism for individual accretionary complex allows the geotectonic subdivision of the Japanese Islands be emended with a new definition of geotectonic units and their mutual boundaries. Removing the effect of arcrelated magmatism and secondary tectonic modification by microplate activities such as backarc basin opening, fore-arc sliver movement, and arc-collision, a remarkable oceanward younging polarity is recognized among the accretionary complexes. This polarity in growth is well observed in Southwest Japan where seven distinct units occur, i.e. from the Japan Sea side to the Pacific side: 400-300 Ma high-P/T schists, Permian (250 Ma) accretionary complex, 230-180 Ma high-P/T schists, Jurassic (180-140 Ma) accretionary complex, 100 Ma high-P/T schists, Late Cretaceous (80 Ma) accretionary complex, and Tertiary (50-20 Ma) accretionary complex. The sinuous surface trajectories of these geotectonic boundaries and occurrence of several tectonic outliers and windows indicate that all these complexes, including high-P/T schists, occur as subhorizontal (or gently northward dipping) thin tectonic unit, i. e. nappe. Thus the Japanese Islands form a huge pile of nappes that become younger structurally downward to the modern Nankai accretionary complex. What is remarkable in this subhorizontal orogen is that high-P/T units are tectonically intercalated between low-P units, e. g. the thin nappe of 100 Ma Sanbagawa blueschists between Jurassic and Late Cretaceous accretionary complexes of the prehnite-pumpellyite facies. Uplift of the Sanbagawa high-P/T unit appears to correlate with the arrival of the Kula/Pacific spreading ridge at the trench, suggesting that this high-P/T accretionary complex may have been extruded and uplifted into low-P domain in fore-arc by buoyant subduction of the spreading ridge at the trench. Evidence of ridge subduction at that time is supported by reconstructed paleoplate motion and the coeval climax of arc-related Ry-oke magmatism associated with low-P/T regional metamorphism. Formation of older high-P/T blueschist nappes sandwiched between low-P units can be explained likewise. Subduction of major spreading ridges seems most critical for the episodic oceanward development not only of subhorizontal high-P/T nappes but also of continent side granitic belts.
著者
久田 英子
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.110, no.1, pp.1-16, 2001
被引用文献数
1

The Vredefort Dome, located in the central part of the Witwatersrand Basin in South Africa, is the type locality for pseudotachylite. Pseudotachylite at the Vredefort Dome is generally regarded to be of impact origin. Pseudotachylites which are closely associated with faults are, however, also known to be common along the northern and northwestern edges of the Witwatersrand Basin. In order to compare pseudotachylites from the Vredefort Dome and from the surrounding Witwatersrand Basin, different studies were undertaken in the past. Mode of occurrence, microscopic textures, geochemical analyses and chronological measurements of pseudotachylites are briefly reviewed in this paper.<BR>In the Vredefrot Dome, pseudotachylites are commonly observed except in the central part of its core. In the surrounding Witwatersrand Basin, they are reported from drill core sections and in underground workings. The matrix in pseudotachylite from the Vredefort Dome is mostly a recrystallized melt phase, while those from the surrounding Witwatersrand Basin seem to be composed of clastic material. Pseudotachylites both from the Vredefort Dome and the surrounding Witwatersrand Basin are geochemically closely related to their host rocks. Although evidence for more than one generation of pseudotachylite has been presented, both in the Vredefort Dome and the surrounding Witwatersrand Basin, it is widely believed that most of them were formed as a result of the Vredefort impact event (<I>ca</I>. 2.0 Ga). Other fault rocks reported from the surrounding Witwatersrand Basin are older than the pseudotachylites and therefore not related to their formation.
著者
吉山 昭 柳田 誠
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.104, no.6, pp.809-826, 1995
被引用文献数
30 15

In this paper the new methodology for quantitative estimation of uplift rates at inland region was discussed using fluvial terrace surfaces and deposit bases. Previous studies have revealed that river profiles regularly changed according to the cyclic fluctuation of climate and sealevel ; therefore, in the interglacial ages (the marine isotope stage 5e and the present) similar profiles with large concavity formed, and in the glacial ages (stage 6 and 2) linear profiles appeared on the contrary. In upper reaches of rivers, stage 5e valley bottoms were filled with the deposit accumulated in the subsequent glacial stages. Based on these observations, the value of relative height between the stage 5e burned valley bottom and the present river floor (BV value) is considered to indicate uplift during those stages (120-130 ky). Similarly, the value of relative height between the stage 6 terrace and the stage 2 terrace (TT value) can be used as an indicator of uplift during the period between those two stages.<BR>The BV values and TT values distributed along Japanese major rivers were reviewed on the basis of previous studies on terrace development and tephro-chronology. In middle reaches of most of rivers, the TT and BV values at the same sites are concordant to each other. The BV values remarkably decrease upstream in spite of no reduction of the TT values in the upper reaches or branches. This implies that present river profiles have not completely been in equilibrium and are now degrading in the upper streams and branches. As an indicator of long-term uplift rate, the TT values have the advantage of applicability to upper reaches and availability of field data in comparison to the BV value. However, it is impossible to apply these methods in the upper reaches or branches where fluvial terraces are not well developed.<BR>Up until now, the uplift rates in mountainous region were presumed from the outlined altitude of mountains or the amount of eroded material trapped in reservoirs, but have not been examined by direct data. The uplift rates obtained by using TT values and BV values are 0.10.8 mm/year in large number of sites, which are not located in very high mountainous area. Large uplift rates more than 1 mm/year were estimated from TT values at the Kurobe river basin, in the northern part of Chubu mountainous region.
著者
浦辺 徹郎 沖野 郷子 砂村 倫成 石橋 純一郎 高井 研 鈴木 勝彦
出版者
Tokyo Geographical Society
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.118, no.6, pp.1027-1036, 2009-12-25
被引用文献数
4 1

Since the discovery of rich microbial communities at and around seafloor hydrothermal sites, their extension towards the oceanic crust beneath the seafloor is of great interest not only for microbial physiology/ecology but also for a wide range of Earth and planetary sciences. How can the communities survive in such an extreme environment? What kinds of metabolism are in action? It is proposed that the sub-seafloor ecosystems are characterized by different kinds of chemosynthetic primary production (carbon fixation), all of which are supported by chemical energy supplied from the sub-seafloor aquifers. We designate the unseen aquifers as sub-seafloor TAIGAs (great rivers) which are responsible for a geochemical flux equivalent to or even larger than that of terrestrial river runoff (<i>e.g.</i> Wheat and Mottl, 2000). Besides, they are responsible for supplying nutrients to microbes beneath the seafloor. We hypothesize that there are four representative TAIGAs based on the chemical energy of compounds of sulfur, carbon (methane), iron, and hydrogen, all of which are supported by the TAIGAs. It is important to note that the sub-seafloor ecosystems are controlled extensively by or are mutually related to the types of TAIGA that flow at the site. The hypothesis can be tested through cooperative research among microbiologists, geochemists, geophysicists, and geologists.
著者
CARNEY Judith HIRAOKA Mario 肥田 登
出版者
学術雑誌目次速報データベース由来
雑誌
地學雜誌 (ISSN:0022135X)
巻号頁・発行日
vol.107, no.1, pp.49-60, 1998
参考文献数
39
被引用文献数
1 1

本論では, アマゾン河の河口部における小農が生計の維持に役立てているジュパチヤシjupati (Raphia taedigera) の意義に関する生物地理的, 社会・経済的研究について述べる。特に, 最近関心のもたれている研究, すなわちアマゾン河流域における森林伐採に取ってかわる方法としての土着の農的林業システム, とりわけ市場向きの生産物を生み出すことと持続可能な土地利用システムを備えているヤシの役割に注目する。これまでの研究においては, アサイヤシaçaí (Euterpe oleracea) の実の市場における経済的有用性に着目した事例は見出せはするものの, 同じ湿潤域に存在するヤシでありながら, ジュパチヤシに着目した研究は皆無に等しい。ジュパチヤシは, 土地の人々に対して数々の有用な恩恵を施しているが, 換金作物としての市場性には欠ける。このような特徴を備えたジュパチヤシは, アマゾン河の河口部ににおいて最も広範囲に見出される。葉柄部の外皮は, 小エビを採る道具・筒の材料に好んで使われている。小エビの販売は, 河口部の河畔に住む現地人・リベリーニョの絶好の現金収入となる。本研究では, アマゾン河下流域におけるジュパチヤシについての植物地理的側面からの概観, ジュパチヤシの繁茂にとっての水文条件, リベリーニョが生計の維持に採り入れているジュパチヤシ利用に関する彼ら固有の知恵についてふれる。