著者

中村 有吾 松本 亜希子 中川 光弘

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.114, no.4, pp.549-560, 2005-12-25 (Released:2009-11-12)

参考文献数

18

被引用文献数

8 6

---

The AD1663 ejecta of Usu volcano, western Hokkaido, northern Japan, have a thickness of approximately 200, cm and are divisible into 7 units on the eastern foot of Usu volcano. The basal deposit, Unit-A, is composed of fine-grained, poorly sorted pumice and ash with well-developed stratification. It contains base surge beds near the sources, and is interpreted as phreatomagmatic in origin. Unit-B is typical in many respects of the product of plinian activity. It is characterized by coarse grain size and wide dispersal, combined with low lithic contents and poor development of internal stratification. This fallout deposit (Usu-b tephra) can be seen in the eastern regions of Usu volcano, and has a thickness of about 4 cm at 200 km from the vent. Unit-C, Unit-E, Unit-F, and Unit-G have characteristics that are satisfactorily interpreted as a consequence of phreatomagmatic activity : fine grain size near source, poor sorting, well-developed stratification and base surge bedforms. Unit-D is typical of phreatic deposits, being composed largely of non-juvenile lithic fragments.According to historical records, the eruption was preceeded by earthquake swarms for 3 days from August 13, 1663. The first eruption (Unit-A) occurred on August 16, followed by an eruption associated with a large amount of pumice and ash (Unit-B) on August 17. The explosive eruptions lasted approximately 20 days.The petrographic properties of the plinian product differ considerably from those of the phreatomagmatic products. The pumice clasts of Unit-B contain abundant glass and little phenocryst (plagioclase, orthopyroxene, and hornblende). The glass has a relatively high refractive index (n = 1.490-1.492) and a low SiO2 content. Orthopyroxene in Unit-B has a relatively high refractive index (γ = 1.735-1.740) and low Mg#. The phreatomagmatic products are rich in massive glass. This glass has a relatively low refractive index (n = 1.475-1.490) and a high SiO2 content, with values differing among horizons. The compositional diversity of the 1663 products indicates the existence of some magma. Presumably, their mixing triggered the 1663 eruption of Usu volcano.

著者

伊藤 孝士 阿部 彩子

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.6, pp.768-782, 2007-12-25 (Released:2009-11-12)

参考文献数

40

被引用文献数

1

---

The climate in the Quaternary is characterized by ice age cycles with periods in the range of tens of thousands to a hundred thousand years, triggered by long-term insolation variations due to the Earth's orbital and precessional motions. Although we can accurately calculate long-term insolation variations at the top of the Earth's atmosphere, we need to know the physical and dynamical processes occurring in the complicated climate system of the Earth in order to understand the true nature and origin of the ice age cycles. In this manuscript, first we briefly review how the gravitational interaction between planets causes insolation variations. Then, we summarize the recent status of large-scale numerical experiments as to how the ice age cycles take place in the climate system of the Earth, with a particular focus on dynamical modeling of ice sheets.

著者

古谷野 裕 早川 由紀夫 町田 洋

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.105, no.4, pp.475-484, 1996-08-25 (Released:2009-11-12)

参考文献数

12

被引用文献数

4

著者

磯崎 行雄 丸山 茂徳

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.100, no.5, pp.697-761, 1991-10-25 (Released:2010-10-13)

参考文献数

195

被引用文献数

186 206

---

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

石橋 克彦

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.102, no.4, pp.341-353, 1993-08-25 (Released:2010-11-18)

参考文献数

52

被引用文献数

4 5 5

著者

田口 洋美

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.113, no.2, pp.191-202, 2004-04-25 (Released:2009-11-12)

参考文献数

60

被引用文献数

2 1

---

It is generally assumed that the Japanese society and culture have been developed on the basis of the agriculture, especially on the rice field cultivation. Hunting, therefore, has been considered a sub-culture insignificant in the socio-cultural context as a whole. The author, however, is of the opinion that the two activities, agriculture and hunting, which are seemingly unrelated in outlook, have been strongly linked and have played complementary roles to each other.Japanese traditional hunters, Matagi, played an important role here as semi-professional hunters, and their hunting has increasingly become market-oriented.Agricultural activities inevitably destroy the natural habitat of wildlife by reclaiming or clearing forests to make the land suitable for cultivation, thus eliminating wild animals. Ironically, however, crops grown on cultivated land, which are rich in nutrition, attract wild animals. If the farmers intend to keep high productivity, those animals must be efficiently expelled from the man-controlled area. Agriculture is simply incompatible with wild animals.Hunting for a living, on the other hand, in essentially to capture wild animals, they are either consumed as various resources by the hunter himself or sold or exchanged for the necessities of life. To ensure sustainable hunting, the number of wild animals must also be sustained, which means the number of captures and the reproduction of animals must be well balanced. Hunting activities thus inevitably require coexistence with wildlife.Hunting and the agriculture, contradiction in principle, however, could and actually have cooperated to form a complementary relationship, which could be called a system : the hunters eliminated wild animals from cultivated land, and the crops attracted game animals for hunting. Around the peripheries of cultivated areas such complementary relationships have been and still are sustained.Historically, such relationships were gradually established from 17th to 18th centuries, when the Edo Shogunate encouraged as its policy to expand agricultural lands. With the technological advances of irrigation systems, marshlands and shoals were turned into rice fields in the plains, and hills and valleys were cultivated in the mountain regions. Hunting then gradually became involved in the agricultural activities to protect farmland from wild animals.In the later period of the Edo Shogunate, the farmers themselves began to capture or chase wild animals out of farmland. At the same time, some hunters with highly professional hunting techniques began further chasing and hunting game animals beyond the cultivated lands. Villages experiencing greater damage from wild animals often hired such hunters. The resources obtained from the captured animals and birds, such as furs, hides, feathers, tendons, meat, and internal organs and bones for medical use, were supplied to the local markets. Hunting thus found its niche at the peripheries of agriculture and the market that demanded animal resources, though limited in quantities and in the number of consumers the market might have been.The flow of animal resources, from agricultural land, to the hunters, then to the market, seems to have been established as a system around 18th to 19th centuries, as the monetary system began to prevail and currency was widely used.As Japan turned into the Modern Ages, hunting became more market-oriented and also strictly controlled : hunting was encouraged to supply furs for export to Europe and the US, and for the military use under the Imperial militaristic government at the time.A historical review of hunting in Japan suggests that, as for the conservation of wildlife, a historical and socio-cultural viewpoint is essential along with ecological and ethological research.

著者

松本 剛 木村 政昭 仲村 明子 青木 美澄

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.105, no.3, pp.286-296, 1996-06-25 (Released:2009-11-12)

参考文献数

27

被引用文献数

6 11

---

Precise topographic features at the two major structural boundaries in the Ryukyu Arc, Tokara Gap and Kerama Gap, revealed that there exists a ridge feature of the Ryukyu Arc as a saddle topography. The feature supports the idea recently proposed that a landbridge connecting the Chinese continent, Ryukyu Islands and Japanese Islands, is thought to have been subsided since Late Pleistocene. The saddle is offset by large-scale left-lateral normal faults both of which are related to the opening of the Okinawa Trough. These topographic features and geological structure together with the gravity anomaly and regional tectonics in the Ryukyu area suggest that a north-south tensional stress regime, due to the rolling buck of the Philippine Sea Plate at the Ryukyu Trench, has dominated in this region since last 20, 000 years.

著者

真鍋 淑郎

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.101, no.6, pp.453-457, 1992-12-05 (Released:2009-11-12)

参考文献数

16

---

This paper describes the response of a coupled ocean-atmosphere-land surface model developed at GFDL to gradual changes of atmospheric carbon dioxide. It summarizes the results in three recently published papers (Stouffer et al., 1989 Manabe et al., 1991, 1992). They represent the current state of the art in predicting further climate change induced by greenhouse gases in the atmosphere.The warming of the coupled system is reduced by the effective thermal inertia of the earth's surface which is essentially controlled by the vertical mixing of heat in the oceans. This study investigates how such vertical mixing of heat is achieved, resulting in the delay of the greenhouse warming in the joint troposphere-continental surface-ocean system.

著者

小林 淳 小山 真人

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.105, no.4, pp.431-447, 1996-08-25 (Released:2009-11-12)

参考文献数

35

被引用文献数

1 1

---

We made a detailed tephrochronological study in the western and southern foots of Hakone Volcano and revealed the eruptive histories of Hakone and other volcanoes since 240 ka. We recognized four widespread tephras, Aira-Tn Ash (AT), Sanbe-IkedaAsh (SI), Kikai-Tozurahara Ash (K-Tz) and Ontake 1 Pumice (On-Pm1) as well as the tephras from the adjacent volcanoes, such as Hakone-Mishima Pumice (Hk-CC4), the pyroclastic flow associated with Hakone-Tokyo Pumice (Hk-TPfl), and Hakone Da-5 Pumice from Hakone Volcano, Fuji Susono-1 Scoria and Fuji Susono-2 Scoria (F-Sul and F-Su2) and Fuji-Yoshioka Pumice from Fuji Volcano, and the tephras from the Higashi-Izu monogenetic volcano field. Eruption ages of F-Su2, F-Sul, Hk-CC4 and F-YP are estimated to be 36 ka, 37 ka, 43 ka and 85 ka, respectively, by loess-chronometry. The discharge mass and eruptive magnitude M are estimated to be 3.7 × 1011 kg and 4.6 for Hk-CC4, and 4.2 × 1011 kg and 4.6 for Da-5 Pumice on the basis of their isopach maps. The eruption frequency in the study area is 0.11 times/ ky for the last 240 ky in average, showing an abrupt increase to 0.53 times/ky during 120 ka-135 ka. In this period, both Hakone Volcano and the Higashi-Izu monogenetic volcano field seem to have been active simultaneously.The loess thickness, which is interbedded between Hk-CC4 (43 ka) and Hk-TPfl (52 ka), tends to increase toward the eastern foot of Fuji Volcano. The age-depth diagram shows that the accumulation rate of loess is nearly constant in each locality except for the rapid increase at about 50 ka in the Kannami area. The linear accumulation of loess supports the validity of loess-chronometry. The 50 ka increase of loess accumulation rate seems to be associated with enlargement of barren plains, which were located in the eastern of Fuji Volcano and were probably the main source of loess materials.

著者

湊 進

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.115, no.1, pp.87-95, 2006-02-25 (Released:2009-11-12)

参考文献数

55

被引用文献数

21 23

---

Nationwide in-situ measurements of terrestrial gamma ray dose rates have been carried out using a scintillation counter. A database of over 4300 entries has been compiled by adding data taken from literature to the data collected by the mentioned survey. A contour map of dose rates in Japan calculated from the database is presented along with a table of dose rates for each bedrock type.

著者

早川 由紀夫

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.104, no.4, pp.561-571, 1995-08-25 (Released:2009-11-12)

参考文献数

11

被引用文献数

7 6

著者

新井 智一

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.114, no.5, pp.767-790, 2005-12-25 (Released:2009-11-12)

参考文献数

47

被引用文献数

5 1

---

This study examines the interaction between the politics in Fussa City and the Yokota Air Force Base, that is “the politics of place, ” from a range of political, economic, and cultural processes which maintain the existence of the base.Military bases are generally established for global geopolitical purposes. However, the establishment of a military base has cultural implications for the local communities where the base is located, i.e., increased concerns about crimes committed by seavicepersons and noise by aircrafts. Although these military bases have some serious impacts, especially in Japan, geographers have not yet examined the issues regarding a particular military base and the resultant politics in the city.On the contrary, since the 1980s, Anglo-American political geographers have paid more attention to “the politics of place” This refers to the local politics that occur due to the interaction between a structural constraint and the individuality of a particular place.Therefore, this study examines “the politics of place” on the Yokota Air Base in Fussa City, Tokyo, by using resources from the local newspapers, novels, magazine articles, and council proceedings.The results are as follows : (1) Owing to the independence between the U.S. Air Force and local political and economic actors, an urban structure and local economy that depended on the Yokota Air Force Base were constructed in Fussa Town after the establishment of the base in 1945; (2) because of this structure, the local economy became to depend on Air Force personnel as consumers; (3) however, due to a shift to the floating exchanging rate and a reduction in the population of the base in the first half of the 1970s, there was a decrease in the influence that Air Force personnel had on the local economy; (4) since the 1980s, an economic agent utilized the “atmosphere” and “image” adjacent to the base to revitalize the local economy; (5) furthermore, the mass media represented Fussa City as a “base town” and conducted a review of the city in the 1960s, thus contributing to its revitalization; (6) during the economic slump in the 1970s, some local political agents were against the existence of the base. However, successive mayors of Fussa City have accepted the existence of the base, and utilized the subsidies it receives from the national government in order to construct the urban infrastructure.

著者

瀬野 徹三

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.114, no.3, pp.350-366, 2005-12-25 (Released:2009-11-12)

参考文献数

27

被引用文献数

2 3

---

Plate motions provide the most basic information on plate tectonics. I explain how to describe plate motions on the Earth mathematically, and how they can be determined. I review the history of the determination of global plate motions, the most recent of which has been derived by space geodetic techniques.

著者

多田 隆治

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.107, no.2, pp.218-233, 1998-04-25 (Released:2009-11-12)

参考文献数

57

被引用文献数

1 1

---

Since the ice core records from central Greenland revealed the presence and significance of millennial-scale large and abrupt climatic changes, widely known as Dansgaard-Oeschger [D-O] Cycles, it becomes the major objective of paleoclimatological researches to clarify their extent, nature, propagation mechanism, and driving force. Although the ultimate driving force is not yet understood, results of recent studies suggest 1) D-O Cycles are global phenomena, 2) they involve complicated interactions and feedback processes among the subsystems including atmosphere, cryosphere, hydrosphere, and biosphere, and 3) they seem tohave initiated from changes in atmospheric circulation.Catastrophic surges of Laurentide Ice Sheet called Heinrich Events are closely associated with D-O Cycles. Although Heinrich Events are likely to have been caused by free oscillationsof ice sheet growth and decay, they were probably not a cause of D-O Cycles but the events seem to have been phase-locked by D-O Cycles. Results of numerical modelling suggest the presence of multi-modes for global deepwater circulation. Switching among the modes is most likely caused by slight variation in hydrogical cycles which change the fresh water balance between Atlantic and Pacific.

著者

西村 蹊二 斉藤 祥 谷岡 誠一 門脇 淳

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.86, no.6, pp.346-363, 1977-12-25 (Released:2009-11-12)

参考文献数

20

被引用文献数

1

---

Detailed and intensive investigations have been carried out on the abrupt failure of submarine slope of a small island, Shin-jima, in Kagoshima Bay, Kyushu on April 1, 1975 by the joint research group of Geographical Survey Institute of Japan, Japan Maritime Safety Agency and Geological Survey of Japan under the sponsorship of Japan Science and Technology Agency.The Shin-jima island emerged from water at the great eruption of adjacent Sakurajima Volcano in 1779 to 1780 (An-ei Eruption) as one of central corns of Aira Caldera (MATSUMOTO, 1933). The island gradually reduced its exposed area by continuous wave erosion to form truncated configuration, being surrounded by broad, shallow, flat tidal bench.Geologically the island is composed of the latest Pleistocene to the earliest Holocene thick loose pumice deposits with intercalations of silt and clay showing inner bay facies. These formations are strongly faulted by eastwest faults. The surface of the island is covered with thin shell bed dominantly composed of Ostrea and andesitic lava. The flat bench around the Shin-jima consists of recent, loose pumiceous drift sand deposits derived from the island by wave erosion.The failure of the slope now in concern occurred at the spit of the southern tip of the island, where thickness of drift sand deposits attains at most about 35 meters according to sonic prospecting and borings at the spit. It was caused by submarine landslide in the thick, loose drift sand deposits. Volume of the slide mass amounts approximately 265, 000 cubic meters.The spit had formed steep submarine slope near critical angle by abundant supply of very loose drift sand from northern part of the island before the failure occurred. Neither sensible earthquakes nor volcanic activities of the Sakurajima which might have given significant effects to submarine landslide are observed and recorded in seismometer around the crucial moment of the failure.Therefore, the cause of the landslide is considered that the increase of load resulted from the deposition of drift sand attaining about 8, 400 tons in volume atop of the slope brought about decrease of safety factor of the slope to make it slide. Wave pressure seems to have triggered the slide because safety factor decreases about 20 % when fluctuation of pressure at the bottom caused by wave agitation is taken into account.

著者

大竹 政和

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.95, no.3, pp.167-185, 1986-06-25 (Released:2009-11-12)

参考文献数

55

被引用文献数

1

---

The essential role of interstitial fluid pressure (pore pressure) in earthquake occurrence is strongly suggested by the observational fact that seismic activity was induced by water injection into a deep well and water impounding of an artificial reservoir. Elaborate studies related to water injection revealed following important characteristics of the induced seismicity : (1) Earthquakes are triggered to occur when the interstitial fluid pressure of the basement rock exceeds some threshold level ; (2) Focal mechanisms of induced earthquakes are in good harmony with the regional stress field ; and (3) Seismic activity propagates as far as several kilometers from the injection well. Based on those observational facts, we conclude that the injected water raising the interstitial fluid pressure releases the tectonic stress naturally accumulated. The effect of pressure change on the fracture strength of rock S is formulated in terms of the effective stress hypothesis asS=τ0+ (σn-P0) tanφwhere σn and P0 are normal stress and interstitial fluid pressure, and τ0 and φ are the coefficient of cohesive strength and internal friction angle, respectively. This criterion of rock fracture may also be applied to account for the reservoir induced seismicity. For the case of reservoir induced seismicity, however, the loading effect of water mass should be taken into consideration since some of the artificial reservoirs exhibit induced aseismicity.The effect of interstitial fluid pressure seems to be essential even for occurrence of natural earthquakes. Detailed studies on the Matsushiro earthquake swarm revealed that the earthquake swarm was brought about by the “water eruption”; high pressure water supplied at the depth beneath Matsushiro erupted to the ground surface accompanying a large number of small earthquakes which were generated by the increase of interstitial fluid pressure. Remarkable upheaval of the focal area, gushing out of large amount of water, and other associated phenomena are consistently interpreted by the water eruption model. It will be of great value for deeply understanding the nature of swarm activity to investigate whether such a mechanism is common or not to other earthquake swarms.The dilatancy-diffusion model of earthquake occurrence is briefly discussed from the viewpoint of the effect of interstitial fluid pressure. The model is a fascinating product of the effective stress hypothesis and results of laboratory experiments of rock fracture. It, however, is still dubious if the results obtained in the laboratory can directly be applied to the earthquake phenomenon occurring in the natural environment. We, therefore, emphasize the especial importance of advanced studies on induced earthquakes which occur under the half-natural and half-controlled circumstances.

著者

吉井 敏尅

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.102, no.4, pp.393-398, 1993-08-25 (Released:2010-11-18)

参考文献数

18

被引用文献数

1 1

著者

新井 健司

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.104, no.2, pp.267-283, 1995-04-25 (Released:2009-11-12)

参考文献数

17

被引用文献数

1 2

---

Plio-Pleistocene fluvial sediments are distributed in the hills along the western margin of the Kanto Plain. In this paper, the author reports its sedimentary environments at Hidaka City, Saitama Prefecture, namely, those of Yaoroshi tuff, Hanno gravel and their correlatives.The basement in this area (Chichibu Paleozoic and Mesozoic formations and Takaoka formation) is divided into three zones structurally by Koma-Hongo and Komagawa fault systems. And terrace deformation dipping toward the Kanto Plain is recognized on its surface.Yaoroshi tuff is in fault or unconformity contact with the basement in part of Koma-Hongo fault system. The vertical displacement of each fault system is over 50 m. Yaoroshi tuff is not distributed in west of Koma-Hongo fault system.Hanno gravel, conformably overlying Yaoroshi tuff, is in fault or unconformity contact with the basement. Hanno gravel and its correlatives were formed by old long rivers, of and the valley bottoms were at least 140 m above sea level in Koma River system area and at least 150 m above sea level in Shukuya River system area.Boulders of granite and diorite characterizing Hanno gravel in the south of Tenran-zan (Mt. Tenran) are not found in the investigated area. This fact suggests that the area was in different conditions of sedimentation from the southern area. The ridge directions of Koma Hills and Moroyama Hills had already settled before dissection proceeded.The gravel from Moroyama Hills and the adjacent areas is divided into the lower and the upper layers. The former is correlated with Yaoroshi tuff, while the latter with Hanno gravel.When Yaoroshi tuff deposited, forested stable land had extended widely. And short rivers flowing out from near mountains sometimes flooded and destroyed forests. After Yaoroshi tuff was formed, long rivers transported boulders with sands in large quantities from distant western mountains. These old long rivers kept their main courses to the present as Koma River system and Shukuya River system, and they mixed gravels by gathering currents and forming talus deposits.

著者

片山 一道

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.105, no.3, pp.384-397, 1996-06-25 (Released:2009-11-12)

参考文献数

29

---

The present paper describes the physical characteristics of Ocean Mongoloid peoples who are indigenous in the Oceania proper, analyses variation patterns among them, and reconstructs the processes that they colonised and settled the oceanic world, following a brief introduction to the human population history in Oceania. Based on the analysis, their remote origins are discussed. The best example of Ocean Mongoloids is the Polynesian population. Polynesians are very homogenous in physique, language and culture. Linguistic and archaeological evidences so far gathered suggest they differentiated into island groups in the past 3, 000 years from a Lapita-associated ancestoral population. Anthropological data show their uniqueness for the large, muscular and robust body form as well as a hyperostotic growth pattern from Homo sapiens standards, and their Asiatic nature in many genetic characters. Accordingly they should be considered “the unique Asian in South Pacific”, and their origins should be sought in Asia. It is highly probable that the Polynesian phenotype was developed during their dispersals into Oceania as the result of adaptation to the specific oceanic habitats humans ever encountered. The speculation here suggests that the remote origins of Ocean Mongoloids were somewhere in circum-China Sea areas, and that some group associated with Jomon people in Japan should be a candidate for their ancestors.

著者

豊 遙秋 春名 誠

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.107, no.6, pp.794-802, 1998-12-25 (Released:2010-11-18)

参考文献数

66