出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.120, no.1, pp.Cover01_1-Cover01_3, 2011-02-25 (Released:2011-05-20)

参考文献数

4

---

(表面)大陸は異なった時代につくられた造山帯のモザイクであるが,平均するとTTG組成をもつ.その大陸地殻は太平洋型造山運動でのみつくられ,現在までに地表面積の1/3を占めるまで増加している.そのほとんどは太平洋型造山運動によってつくられた.大陸の衝突による造山運動は既存の造山帯を変形再結晶させるだけで増加させることはない.大陸の造山帯のモザイクは,大陸の歴史を直接反映し,大陸地殻の形成プロセスを記録している. (裏面)第1大陸と第2大陸はTTGで構成されるが,第3大陸はアノーソサイト組成である(Kawai et al., 2009).第2大陸の分布はアジア大陸の下で最大のサイズに発達している.それは遷移層最下部(520-660km)だけでなく,下部マントル最上部にも漂移している.太平洋とアフリカ大陸直下の2つのスーパープルームとアジア直下の大下降流が地球内部の大局的なマントル対流である(Maruyama, 1994; Maruyama et al., 2007a, b).(丸山茂徳)

著者

早津 賢二

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.102, no.5, pp.611-613, 1993-10-25 (Released:2009-11-12)

参考文献数

10

著者

長岡 信治 古山 勝彦

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.113, no.3, pp.349-382, 2004-04-25 (Released:2009-11-12)

参考文献数

32

被引用文献数

5 9

---

Many basaltic monogenetic volcanoes forming groups are distributed on Fukue Island, the largest island of the Goto Islands. The Onidake volcano group, 8×10 km across, is one of the monogenetic volcano groups in the island. It contains eleven monogenetic volcanoes, namely, Daienji, Koba, Nagate, Masuda, Shimosakiyama, Hinodake, Kamiozu, Shirodake, Sakiyamabana, Midake-Usudake, and Onidake, in chronological order. K-Ar and 14C dating results show that these volcanoes were active during 0.5-0.018 Ma. The average interval of monogenetic volcano-forming eruption is fifty thousand to thirty thousand years, while a long interval of about one hundred thousand years exists between 0.25 and 0.15 Ma. By long interval, the group is divided into older volcanoes, Daienji, Koba, Nagate, and Masuda, and younger volcanoes, Shimosakiyama, Hinodake, Kamiozu, Shirodake, Sakiyamabana, Midake-Usudake, and Onidake.At about 0.42 Ma, the activities of the older volcanoes started with Daienji volcano, which produced a lava flow in the north area. It was covered by thick lava flows of Koba volcano at about 0.38 Ma. During or shortly after the activity of Koba volcano, Nagate shield volcano with two small scoria cones became active in the northeastern area. At about 0.30 Ma, in the western area, Masuda volcano erupted to form a lava plateau and two scoria cones.After 0.15 Ma, in the central area, the intermittent activities of younger volcanoes began with lava flows from Shimosakiyama volcano, which was covered soon by Hinodake volcano composed of three lava flows and one scoria cone. Two small cinder cones with a lava flow, Shirodake and Kamiozu volcanoes, erupted on the northern part of Hinodake volcano. At about 0.03 Ma, at the southeastern end, Midake-Usudake volcano, erupted with three cindercone-forming scoria falls and five small plateau-forming lava flows covering an undated scoria cone, Sakiyamabana.At 0.018 Ma, the latest eruption of the group, Onidake volcano, commenced in the central area, the first phase of which was the Abunze lava flow originating from welded scoria falls or a mixture of lava and scoria fall into the lava ponds in craters. Simultaneously, the scoria falls generating Abunze lava flow contributed the formation of Osako scoria cone, which partially collapsed shortly afterwards, probably because Abunze lava carried the parts away. In the second phase, Onidake scoria falls covered a large area of 5×5 km, while Onidake scoria cone was formed in the proximal area. The third phase consisted of five lava flows, Ohma lava 1, 2, and 3 and Onidake lava 1 and 2, all of which erupted from two summit craters of Onidake cone and covered the northern and western foothills of the volcano.

著者

丸井 敦尚

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.123, no.2, pp.172-181, 2014-04-25 (Released:2014-05-16)

参考文献数

22

被引用文献数

2

---

The Kanto Plain is the biggest and deepest groundwater basin on the Japanese Islands. The water in the basin has been used in various purposes, and the volume of use is estimated to be the greatest in the country. Consequently, severe problems have emerged in the history of water development and water environment protection. The study show two stories in the groundwater basin of the Kanto Plain, corresponding to depth. The deeper one emphasizes salt water containing natural gas, and the shallow one is characterized by the largest groundwater flow system in the country. The paper reviews the geological features of the basin. Groundwater condition, especially deep groundwater, is also reviewed to understand the next stage of activities to develop and protect the environment.

著者

藤岡 換太郎

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.97, no.1, pp.39-50, 1988-02-25 (Released:2009-11-12)

参考文献数

59

被引用文献数

1 2

---

Topographic features around Izu Oshima region were summarized with special references to the characteristics relating to subduction of the Philippine Sea plate (PHS) along the Sagami Trough. Several topographic highs having circular contours around Oshima Island may be the results of parasitic eruption of Oshima Volcano. Their trend is almost parallel to the elongation of the linearity of parasitic cones distributing onshore. Along the eastern trench slope off Oshima Island, large scale collapse structures are seen in the submarine topographic map. These are the result of the falling down mostly of pyroclastic materials (tephras) during historic ages. The Oshima Island shows eastward tilting owing to the bending resulted from the subduction of the PHS. Large scale of the collapse structures may be caused by the oversteepening of the eastern trench slope of Oshima Island and soft sediments consisting mostly of pyroclastics including a large quantity of pore water slide down along the trench slope as far as the Sagami Trough.Radial distribution both of saddles and valleys observed northeastern offshore part of the Oshima Island may be lava flows and/or dike swarms derived from the old Okata Volcano whose eruption center was estimated to exist at the northeastern extension of the Oshima Island.About 4 km south off the Oshima Island, large scale of the topographic breakes consisting of caotic highs and depressions are seen in the submarine topographic map. These may be debris flow deposits along eastern slope of Ohmurodashi which consists mostly of the Quaternary rhyolites geologically and chemically similar to those exposed on the Niijima and Kozushima Islands. These are the results of catastrophic phreatomagmatic eruption of the Ohmurodashi such as that of the Myojinsho. Mixture of pyroclastics and lavas will be found from these caotic areas.The upper steam of the Sagami trough shows notable meandering whose direction is almost parallel to that of the movement of the PHS east off Oshima Island and almost perpendicular east off Ohmurodashi. At the latter case, thrust structures may trace along the subduction zone at the landward slope of the Sagami trough. Just landward side of the thrust, curious round topographic highs can be observed. They may be mud volcanoes.Topographic features observed around Oshima Island may best be understood in term of the normal and oblique subduction of the Philippine Sea plate along the Sagami Trough.

著者

尾方 隆幸

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.120, no.5, pp.viii, 2011-10-25 (Released:2012-01-17)

参考文献数

1

著者

鵜川 元雄 藤田 英輔 熊谷 貞治

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.111, no.2, pp.277-286, 2002-04-25 (Released:2009-11-12)

参考文献数

13

被引用文献数

6 12

---

Continuous seismic observations at Iwo-jima, an active volcanic island belonging to the Izu-Ogasawara island arc, have detected remote triggering of microearthquakes in and around the island. The remote triggering at Iwo-jima is a phenomenon of an abrupt increase of microearthquake activity at the time of a passage of seismic waves from a distant large earthquake. We examined seismograms of a total of 21 earthquakes with magnitude larger than 7 and within an epicenter distance of 3000 km from Iwo-jima. Remote triggering phenomena were found at four events during the period from 1980 to 1993 : the 1983 west off Tohoku earthquake, the 1984 southeast off Kyushu earthquake, the 1993 southeast off Hokkaido earthquake, and the 1993 Mariana Island earthquake. The largest epicenter distance among them was 2009 km. The initial times of triggering coincide with the theoretical arrival times of surface waves and successive occurrences of earthquakes continued for 6 to 15 min, suggesting that dynamic stress or strain caused the remote triggering phenomena at Iwo-jima. As a well-developed hydrothermal system is suggested in shallow depths beneath Iwo-jima, volcanic fluids presumably play an important role in remote triggering.

著者

當舎利行

出版者

東京地学協会

雑誌

地学雑誌

巻号頁・発行日

vol.117, no.4, 2008

著者

三上 岳彦 大和 広明 広域METROS研究会

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.120, no.2, pp.317-324, 2011-04-25 (Released:2011-06-30)

参考文献数

10

被引用文献数

10 16

---

This paper describes our newly developed high-resolution temperature observational system called Extended-METROS, which has been deployed in the Tokyo Metropolitan Area since 2006. Some climatological mean temperature charts using Extended-METROS data are analyzed in terms of urban climatology, and detailed urban heat island temperature patterns are clarified. Rainfall measurements were set up from August 2010 at 40 points in the Tokyo Metropolitan Area. The relationship between urban heat islands and local-scale heavy rainfall patterns in urban areas will also be analyzed based on our high-resolution meteorological observation system.

著者

藤井昭二

出版者

東京地学協会

雑誌

地学雑誌

巻号頁・発行日

vol.113, no.3, 2004

著者

岡田 篤正 安藤 雅孝 佃 為成

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.96, no.2, pp.81-97, 1987-04-25 (Released:2010-02-25)

参考文献数

35

被引用文献数

6 2

---

Four trenches (Trenches A-D) were explored across the Yasutomi fault (a strand of the Yamasaki fault system) to date recent past faultings. Trench A was 3 m deep and 28 m long across the fault (Upper in Fig. 3 and Fig. 4), and the additional excavation was made down to 5 m deep (Fig. 5) from the western wall of trench A. The sizes of other tenches are similar to that of trench A. Since this site was being developed after this trenching for the building lot of a factory, many pieces of important geological evidence were gradually exposed with progress of the construction. This enabled us to make a further detailed geological and geomorphological study of the Yasutomi fault. The results are summarized as follows : 1) Yasutomi fault, which has been considered to be predominantly left-slip active one estimated from tectonic morphologies, was geologically confirmed that this had dislocated with predominantly lateral-slip component at least since a few tens of thousand years.2) Widely sheared zones appeared along the north side of the active trace do not accompany any tectonic features. Therefore, this straightly trending depressional zone is to be recognized as a fault-line valley. A new fault was originated along the southern rim of pre-existed weak zone probably since the late Quaternary.3) The valley-filling deposits are disturbed at the lower part of the trench but not at the upper part this suggests that the fault has not moved since the deposition of the upper horizon although small earthquakes have been reported to occur frequently around the fault. Sense and amount of vertical offset, drugged structure and other fault features vary laterally along this, as common in high angle strike-slip fault.4) The latest displacement occurred between late 7 th and 12 th Centuries, probably associated with the 868 Harima Earthquake (M=7.1). Two more faultings were also inferred from C-14 dates of disturbed and undisturbed strata within a deformed zone of the fault, although they are less reliable. The recurrence interval of earthquakes as large as the 868 event is estimated to be at least 1000 or possibly a few thousand years along this strand of the Yamasaki fault system.

著者

木下 良

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.110, no.1, pp.115-120, 2001-02-25 (Released:2009-11-12)

参考文献数

24

著者

藤原 咲平

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.29, no.12, pp.769-783, 1917-12-15 (Released:2010-10-13)

著者

藤原 咲平

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.29, no.11, pp.701-712, 1917-11-15 (Released:2010-10-13)

著者

北里 洋

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.107, no.2, pp.258-273, 1998-04-25 (Released:2009-11-12)

参考文献数

87

被引用文献数

1 1 1

---

To analyze oceanic paleoenvironmental histories, paleoceanography has used various biological proxies such as characteristic species, molecular bio-markers, chemical components and others. Much of paleoceanographic information originates from skeletal remains and/or chemical compounds of marine organisms. Accordingly, we are always faced with the biological problem of so-called “vital effects”. Experimental paleontology is a research method to determine relationships between organisms and their biotic and / or abiotic environments through well-controlled culture experiments. This is one of the best ways to shed light into the “vital effect” black box.In this article, I review previous studies which have tried to solve paleontological problems through culture experiments using foraminifera. There are three different scales of experimental methods. First is a culture in a petri dish. This method is advantageous to observe the relation between individuals and environmental factors. Second is micro-and mesocosm experiments which tried to reconstruct a part of the marine ecosystem in laboratory. With this method one can examine interactions between organisms and biotic and/or abiotic factors. Third is in situ experiment in the sea using submersibles or benthic landers. These methods play the role of finding clues about, or proving the nature of, currentbiological proxies of paleoceanography. I strongly invite young scientists to work with experimental cultures for the better understanding biological proxies in paleoceanography. Several suggestions for future studies are also proposed in the text.

著者

吉野 正敏

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.6, pp.836-850, 2007-12-25 (Released:2009-11-12)

参考文献数

91

被引用文献数

3 4

---

Recent studies on climate change during the historical period are reviewed in this paper. Firstly, methods, limitations and materials for reconstructing past climates are summarized. Historic diaries and old documents are useful particularly for the period of the past 500 years. Some indices for expressing the climatic conditions found in the historic materials are introduced. Historic documents and materials found in China since 4, 000 BP were published in 2004. On the other hand, daily weather data at several stations for the 15 and 16 centuries in Japan were published in 2004 and 2006, respectively. Secondly, the “Little hypsithermal (warm) period” during the period from the 4th century to the 10th century is described. In the final part of the present paper, examples of an ancient central government in Japan, planning of Heijoukyou (an old center of government), settlements developed on the Boso Peninsula, Chiba, Japan, and parallel activities in Southeast Asia are discussed in relation to the changing climate during the “Little climatic optimum” from the 8th century to 9th century, which was the peak of the “Little hypsithermal (warm) period”. It is pointed out that the changes were roughly in parallel.

著者

澤柿 教伸 平川 一臣

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.107, no.4, pp.469-492, 1998-08-25 (Released:2010-10-13)

参考文献数

120

---

Geomorphological and sedimentological processes beneath modern glaciers and ice sheet s have not been observed directly and are poorly understood. On the contrary, abundant glacial landscapes can be observed, which provide us with evidence about processes underway at the beds of the past ice sheets. Consequently, careful studies of glacial landforms and sediments provide a wealth of information of these processes.During the last decade, there have been various debates regarding subglacial landforms and their formation processes: drumlins is a major issue, and no satisfactorye xplanation of their mode of formation has yet been obtained. By overviewing recent research on the drumlin problem, this article attempts to draw attention to the major concepts and controversies behind the formation of subglacial landform, together with new developments in understanding the subglacial environment. The most recent explanations for drumlin formation have been examined in the light of our knowledge of the subglacial environment. In particular, J. Shaw and his co-workers draw attention to the significance and the implication of subglacial meltwater processes. They suggested that large-scale meltwater floods were responsible for the formation of some drumlins. Later, erosional drumlins, bedrock erosional marks, tunnel channels, and Rogen moraine were added to the forms resulting from catastrophic floods. Conversely, G.S. Boulton developed a semi-quantitative flow model for the deformation of rapidly deforming soft sediments (A-horizon) on the basis of field observations.The drumlin problem stands as a conspicuous instance of how much there is still to understand about the interplay of glacier motion, sediments, topography, and subglacial environmental conditions. It is thus emphasized that accumrate explanations of the complexities of subglacial environments are necessary to understand subglacial landform development, sediment deposition, and other geomorphic processes at the ice/bed interface, together with extraglacial effects of ice sheet dynamics on fluvial systems, marine sedimentation, ocean currents, and climate.

著者

丸山 茂徳 宇都宮 敦 石川 晃

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.120, no.6, pp.1035-1044, 2011-12-25 (Released:2012-03-05)

参考文献数

16

被引用文献数

1

---

オントンジャワ海台は太平洋中央部の太平洋スーパープルームによって白亜紀(122 Maと90 Ma)につくられた巨大な海台である。形成後,西方に移動し,オーストラリアプレートが北上することによってプレート相対運動が変化して,20-25 Maごろから海溝に沈み込みはじめた。その結果,ソロモン諸島には,それらの海台の破片が付加体として露出している。付加しはじめた時期については異論があり,これまでの多くの研究者は2 Ma 以降であると考えてきた。 しかしながら,われわれは地質調査と文献に基づいた証拠,すなわち一連の逆断層の形成と構造浸食,および20-25 Ma以降の沈み込み帯火山活動の停止から以下の解釈を行った。海台が25-20 Maに海溝に沈み込みを開始すると,海台のその浮力のために、沈み込み角度が低角度になり島弧火山活動が停止した。そして始新世以降の付加体を構造浸食して,崩壊物をマントルへと運んだ。また中新世におけるオントンジャワ海台の衝突と沈み込みが背後のウッドラーク海盆の拡大の開始のトリガーになったと思われる。 過去25-20 Maにわたるオントンジャワ海台の沈み込みは,付加体としては海台のごく一部(< 1%)のみを上盤側のプレートに付加したのみで,主要部のほとんどはマントル深部へ沈み込んだと思われる。これは顕生代の環太平洋造山帯に普通にみられる現象である。

著者

山口 貞雄

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.44, no.10, pp.549-561, 1932-10-15 (Released:2010-10-13)

参考文献数

12

著者

早川 由紀夫

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.108, no.4, pp.472-488, 1999-08-25 (Released:2009-11-12)

参考文献数

94

被引用文献数

3 9