著者

小山 真人 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.105, no.2, pp.133-162, 1996-04-25 (Released:2009-11-12)

参考文献数

50

被引用文献数

17 17

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We reveal the detailed syn-and post-caldera eruptive history of Izu Oshima Volcano, Japan, by tephra and loess stratigraphy. Twenty-four tephra layers, which overlie the slope outside the caldera, show that 24 eruptions occurred since the formation of the caldera (about 1, 450 years ago). These eruptions are separated by 10-200 years clear dormant periods, which can be identified by eolian dust (loess) interbedded with tephra layers. The 24 eruptions can be classified into three types : 1) eruption with scoria and ash falls (12 eruptions), 2) eruption only with scoria falls (7 eruptions), and 3) eruption only with ash falls (5 eruptions). While tephra discharge mass of the type 1 is generally large (1.5×1010 to 7×1011 kg), that of the type 2 or 3 is small (0.6 ×109 to 1 ×1011 kg). The 1986 eruption is classified into the type 2. Debris avalanches, which occurred just before the caldera formation and covered almost all of the Izu Oshima island, demonstrate that the present caldera wall was formed by slope failure of an old edifice. The tephra-discharge stepdiagram, which shows a relationship between time and cumulative discharge volume / mass of magma, shows : 1) the average tephra-discharge rate is constant (92 kg/ s before the N1.0 eruption and 25 kg/s after the N1.0 eruption), showing an abrupt decrease of the rate at about the time of the N1.0 eruption, which occurred about 900 years ago and was the most voluminous eruption for the past 1, 450 years, 2) both before and after the N1.0 eruption, the type 1 eruption shows volume-predictability, that is, the discharge volume / mass of a next type 1 eruption can be predicted, 3) a type 1 eruption should occur sometime in the future again, and when it occurs, the discharge mass of tephra should attain to as much as 2×1011 kg or more.

著者

長谷川 昭 中島 淳一 内田 直希 海野 徳仁

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.122, no.3, pp.398-417, 2013-06-25 (Released:2013-07-08)

参考文献数

60

被引用文献数

1 1

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Recent investigations based on seismic tomography, hypocenter determinations and focal mechanism analyses using dense seismic network data reveal the precise configurations of the Pacific (PAC) and Philippine Sea (PHS) plates subducting beneath the Tokyo metropolitan area. Estimated geometry shows a broad contact zone between the two plates located directly beneath the Kanto plain. The overlap with the PHS plate subducting above it provides the PAC plate with protection from being heated by the hot mantle wedge. Moreover, the fore-arc portion of the PHS plate, before its subduction beneath Kanto, had been cooled by the subduction of the PAC plate from the Izu-Bonin trench. These cause lower-temperature conditions within the two oceanic plates and the upper continental plate beneath the Tokyo metropolitan area. As a result, depth limits of seismic activities within the plates and along their boundaries are anomalously deep. Seismic tomography studies show that the easternmost portion of the PHS slab mantle is serpentinized. The PHS slab may have been torn in two along the western boundary of this serpentinized mantle, with the eastern portion being left behind relative to subduction of the western portion. This is accompanied by the generation of large intraslab earthquakes along the boundary. We need to take these observations into consideration to understand the mechanism generating M7-class earthquakes, which are anticipated to occur in the southern Kanto region with a high probability.

著者

篠田 謙一

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.118, no.2, pp.311-319, 2009-04-25 (Released:2010-04-01)

参考文献数

29

被引用文献数

1 3

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Modern DNA—maternally inherited mitochondrial DNA and paternally inherited Y-chromosomal DNA in particular—is now routinely used to trace ancient human routes. It appears that genetic data can actually offer a means of better understanding ancient population movements. The DNA patterns of present-day world populations indicate that modern humans emerged from Africa at least 150,000 years ago. These populations dispersed from Africa to most other parts of the world at least 60,000 years ago along the tropical coasts of the Indian Ocean to Southeast Asia and Australasia. Genetic data support a model for the peopling of the New World in which Native American ancestors diverged from the Asian gene pool and experienced a gradual population expansion as they moved into Beringia. After a long period in greater Beringia, these ancestors rapidly spread into the Americas at least 15,000 years ago. Examinations of ancient human bones using molecular genetic techniques provide direct access to genetic information on past populations. The retrieval and analysis of ancient DNA is more difficult than that of modern DNA. However, this technique holds great potential for inferring the origins of the Japanese people. The distribution of mitochondrial DNA haplogroups among the Jomon, Yayoi, and modern Japanese populations suggests that the formation of the Japanese population was not the result of a population expansion. Distinctively different frequencies of mitochondrial DNA haplogroups among Jomon and Yayoi populations indicate significantly different population histories for these groups. However, both populations have contributed to the formation of the modern Japanese population. An eastward population expansion from the Asian Continent during the Yayoi period resulted in the admixture of these people with the indigenous Jomon people and led to the formation of the basic pattern seen in modern Japanese people.

著者

金田 楢太郎

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.1, no.9, pp.410-415, 1889-09-25 (Released:2010-10-13)

被引用文献数

2

著者

堀 和明 斎藤 文紀

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.112, no.3, pp.337-359, 2003-06-25 (Released:2009-11-12)

参考文献数

141

被引用文献数

9 14

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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.

著者

藤本 強

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.90, no.2, pp.122-136, 1981-04-25 (Released:2010-11-18)

参考文献数

30

被引用文献数

1 1

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The Satsumon culture was in existence in Hokkaido from 9th to 13th century A.D. as a Pre-Ainu culture of Hokkaido. The Satsumon culture succeeded the Post-Jomon culture. The Satsumon culture was formed on the basic cultural elements of the Post-Jomon culture. Some cultural elements from Japanese culture of that time were added to them. The basic cultural elements of the Post-Jomon culture had their roots in late or the latest Jomon culture in northern Japan. So, the Satsumon culture can be regarded as one of the direct descendants of the late or the latest Jomon culture in the northern Japan.About two thousands years ago, rice cultivation began in Japan. At first, rice cultivation was practised in southwestern Japan and it gradually expanded to the east. Finally, it reached the southern Tohoku district, but it could not penetrate into northern Tohoku and Hokkaido. In the northern Tohoku and Hokkaido, people lived on fishing, gathering and hunting as was the case in the previous Jomon period. After the introduction of rice cultivation, the livelihood of people in Japan was separated into two different ways. In most parts of Japan, in southern Japan, people depended on rice cultivation and in the northern extremity of Japan, people lived on fishing, gathering and hunting.

著者

早川 正巳

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.81, no.1, pp.27-47, 1972-02-25 (Released:2010-02-25)

参考文献数

7

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人工地震・地震探査あるいは地震探鉱という言葉はすでに我々には耳なれたものであるが, 案外, その利用や現状については知られていないこともある。編集委員会からの要望に応えて, ここに筆をとつた。利用などかなり広範囲なので不充分な点があると思う。おゆるしいただきたい。上にしるした三つの言葉の意味は, 大体同じようなものであるが, はじめの方ほど広い意味ぐらいにとつてもらえばよかろう。本文でははじめの人工地震を用いることにする。人工地震はどのようにして発展してきたのであろうか, 最初は石油, 石炭などの地下資源をしらべることから始まつたのであるが, 次第にその応用も広まり, 更には地殻の構造解明にまで発展してきた。そのためには陸地のみならず, 海洋においての人工地震の技術が大いにあずかつて力となつたのである。ここではまず, 前半ではこれらの人工地震の歴史をひもとき, またその歴史と関連して, その技術の進歩が如何にその時々の関連学問, 技術の発展や社会情勢の影響をうけたかをふり返つてみる!後半では人工地震でしらべられる構造をその規模の大小に応じて, 小さな方から順次大きな方に実例を用いて説明してゆくことにする。

著者

佐藤 崇徳

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.124, no.1, pp.137-146, 2015-02-25 (Released:2015-03-11)

参考文献数

9

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Although it is necessary to understand map projection to read a map of the world and view the world (surface of the Earth) accurately, geography teachers tend to avoid teaching map projection because they think it is both difficult to understand and to teach. Information technology provides more effective and attractive teaching methods and materials. Shadow images of the globe created by a light source are often used to explain map projection, but this method is not so effective. Transforming globe gores (polyconic projection gores) into various projections is better way to illustrate map projection. Computer software can be used to draw maps of the world using various projections, and to make digital images that illustrate map projections and the order of projections for teaching purposes. They can then be published as educational materials on the Internet. Web pages are constructed to teach the distortion inherent in a Mercator projection map with Google Maps API and Google Earth API. One of these Web pages shows users the great circle line and the rhumb line between any two points on Google Maps (Mercator projection) and Google Earth (digital globe). Another shows users equidistant circles and cardinal and inter-cardinal directions from any point on Google Maps and Google Earth. Teachers and students located anywhere can access the Web pages and study using these on-line materials.

著者

沢田 輝 磯﨑 行雄 丸山 茂徳

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.127, no.5, pp.705-721, 2018-10-25 (Released:2018-11-14)

参考文献数

116

被引用文献数

2 3

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The extensive occurrence of a felsic continental crust is one of the unique features of the Earth. The growth history of the continental crust has been a key issue in understanding the origin and evolution of the Earth. In particular, recent geological studies indicate that subduction of the continental crust into the mantle has been greater than previously imagined. The current understanding of the growth of continents and the differentiation of the crust and the mantle of the Earth is reviewed based on a detrital zircon geochronology. One of the most important achievements arises from the analysis of the age structure of individual continents and secular changes over time. The new detrital zircon geochronology suggests that the sizes of the continents have changed over time, which has been an important factor in the growth of the continents. Large continents, such as the modern examples, can preserve older crusts in their interiors, which are separated from active continental margins. Conversely, in the early Earth, continents were probably formed by the amalgamation of small fragments of crust, such as oceanic island arcs. It is speculated that the smallness of the continents was the most significant cause of the poor preservation of Hadean and Archean crusts, despite putative expected active crustal production. Consequently, the recycling of the continental crust occurred in great magnitudes during the early Earth's history. The large-scale subduction of felsic crust represents one of the most important aspects in studies of the early Earth.

著者

古村 孝志 竹内 宏之

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.3-4, pp.431-450, 2007-08-25 (Released:2009-11-12)

参考文献数

48

被引用文献数

5 6

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The Tokyo metropolitan area is known to have been struck by large earthquakes due to the subduction of the Philippine Sea Plate and the Pacific Plate beneath the North American plate. Recent damaging earthquakes that occurred beneath Tokyo include the 1855 Ansei Edo earthquake, the 1894 Meiji Tokyo earthquake, and the 1923 Kanto earthquake. Whereas the Kanto earthquake is known to have occurred at the top of the subducting Philippine Sea Plate, the other events are considered to have occurred in Tokyo bay, but their source depths are unknown. Many researchers have attempted to determine the source mechanisms of these earthquakes through analyses of patterns of seismic intensity distribution in the Kanto area, but the intensity pattern at the center of Tokyo would be considerably affected by the site amplification effect of the shallow, localized structure rather than be related directly to the source itself. In the present paper, we summarize the characteristics of strong ground motions and damage caused by the earthquakes. We then compare the pattern of intensities on local and regional scales with those of recent earthquakes occurring in Tokyo and corresponding computer simulations using heterogeneous crust and upper-mantle structure models below Tokyo to find referable source models for the Ansei Edo and Meiji Tokyo earthquakes.

著者

小泉 格 坂本 竜彦

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.119, no.3, pp.489-509, 2010-06-25 (Released:2010-08-30)

参考文献数

113

被引用文献数

7 8

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Annual sea-surface temperatures (SSTs) (°C) were derived from a regression analysis between the ratio of warm- and cold-water diatoms (Td' ratio) in 123 surface sediment samples around the Japanese Islands and measured mean annual SSTs (°C) at the core sites. The cross spectra between the atmospheric residual 14C (‰), and annual SSTs (°C) of cores DGC-6 (Japan Sea) and MD01-2421 (off Kashima), respectively, consist of five dominant periods: 6000, 2400, 1600, 950, and 700 years. The amplitude of fluctuations of annual SSTs (°C) in the millennial time scale during the Holocene after the Younger Dryas is within 6-10°C. Periodic variations of annual SSTs (°C) can be correlated within error to abrupt climatic events reported from different paleoclimatic proxy records in many regions of the Northern Hemisphere. The cooling time of annual SSTs (°C) also corresponds to the triple events of high 14C values in the atmospheric residual 14C records, as well as the Bond events in the North Atlantic.

著者

相馬 清二

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.84, no.4, pp.204-217, 1975-08-25 (Released:2009-11-12)

参考文献数

8

被引用文献数

3 3

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A violent fire-tornado has broken out at the former site of the Army Clothing Depot in combustion caused by the destructions of the Great Kanto Earthquake at 3.30 p.m. September 1, 1923. By this fire-tornado, about 40 thousand people have been burned to death in a moment. An interpretation that the fire-tornado has been caused by passage of a cold front has generally dominated academic circles in this field up to date. According to the detailed reexaminations, this interpretation included many inconsistencies. We could obtain recently the various data with respect to the fire-tornado which occurred in the last several years. From these data, it became clear that the fire-tornadoes often have occurred near a combustion area.An example which was the most similar with the fire-tornado at the former site of the Army Clothing Depot was found out in the combustion of Wakayama City by an air raid on July 9, 1945. 748 persons have been burned to death by the fire-tornado in this city.Finally, our study leads to the conclusion that the fire-tornado at the former site of the Army Clothing Depot was caused by the widespread great fire following the Great Kanto Earthquake. There was a cold front in northwestern direction of Tokyo, but it did not play the leading role for formation of the fire-tornado.

著者

松本 良 青山 千春

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.129, no.1, pp.141-146, 2020-02-25 (Released:2020-03-17)

参考文献数

5

被引用文献数

3 5

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An initial estimate of the amount of methane carried by a single methane plume was calculated to be 4 × 109 g (4,000 ton CH4) to 2 × 109 g (2,000 ton CH4) per year (Aoyama and Matsumoto, 2009), based on quantitative echo sounder measurements of the methane plume and bubble capture and release experiments. The estimate generated considerable interest because it suggested the potential importance of plumes as natural gas resources. However, a critical mistake in the calculations was found in converting mole amounts to weight of methane. Revised and corrected estimates of annual methane transported by a single plume are between 2.63 × 106 g (2.63 ton CH4) to 1.60 × 106 g (1.60 ton CH4), which are only 0.07% to 0.08% of the original estimates. For comparison, the revised amount of methane discharged from an individual methane seep is estimated based on direct measurements of gas bubbles from seep sites at Joetsu Knoll and Umitaka Spur, Joetsu basin. A total of 200 ml to 1,150 ml of bubbles were captured within 642 to 481 seconds. Total gas flux depends on the composition of the bubbles. Assuming pure gas, the annual discharge is estimated to be 0.71 ton to 4.84 ton CH4. If the bubbles consist of pure hydrate, the seepage is slightly higher at 1.15 ton to 8.83 ton CH4 per year.

著者

柳井 修一 青木 一勝 赤堀 良光

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.119, no.6, pp.1079-1124, 2010-12-25 (Released:2011-03-17)

参考文献数

121

被引用文献数

25 64

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Median Tectonic Line (MTL) and Fossa Magna (Itoigawa-Shizuoka Tectonic Line) had long been considered to be the most critical fault boundaries controlling development of the Japanese Islands since Naumann (1885) and Kobayashi (1941). After the appearance of plate tectonics, several new interpretations emerged, e.g., sub-surface Benioff plane for the MTL. In this paper, we propose that those tectonic lines, major faults, and Tanakura Tectonic Line (TTL) were formed through a process at micro-plate boundaries during the opening of the Japan Sea in the Miocene. MTL could have been formed along the consuming boundary between the PHS plate and Japan Sea microplate, which has shifted southward to the Nankai trough, accompanying large-scale tectonic erosion. Fossa Magna was formed as a gigantic transform fault with a transtension component in the Medial-Japan Sea when opening was initiated. The eastern and western boundaries of the Japan Sea must be a strike-slip fault, corresponding to TTL to the east, and a newly proposed strike-slip fault called the West Kyushu Tectonic Line, respectively. Fossa Magna, a medial region defined by two NS-trending Miocene parallel faults in central Honshu, defined by Nauman (1885) could be interpreted to be the largest transform fault in the Medial-Japan Sea to offset the spreading axis when the Japan Sea opened. It should be emphasized that large-scale tectonic erosion occurred in front of consuming plate boundaries facing the PHS and PAC plates oceanward during the opening of the Japan Sea. The volume of tectonic erosion is calculated to be 17,581,500 km3, which is equivalent to 2/3 of the present-day Japan arc crust, which is sufficient to reach the depth of the megalith between the upper and lower mantle boundary, even with 10 km thickness of materials eroded and transported along the Benioff zone. Although MTL, Fossa Magna, and TTL are remarkable in the geology of Japan, these young faults never affected the orogeneses of Japan back to 520 Ma, which grew the continental crust of Japan. We propose that microplate boundary processes decreased the volume of the Japan crust.

著者

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.2, pp.Plate6-Plate8, 1996-04-25 (Released:2009-11-12)

著者

高橋 雅紀

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.115, no.1, pp.116-123, 2006-02-25 (Released:2009-11-12)

参考文献数

13

被引用文献数

21 56

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The Euler pole position of the Philippine Sea Plate (PHP) relative to the stable Eurasian Plate (EUP) between 15 and 3 Ma can be estimated at around 150°E, 36°N, on the basis of the geological constraint that the intersection of the Izu-Ogasawara Arc with Southwest (SW) Japan has not moved from South Fossa Magna since 15 Ma. The timing of the migration of the Euler Pole to its present location (154°E, 47°N) should have occurred at 3 Ma because the fore-arc basin in SW Japan was once interrupted by the Kurotaki Unconformity at 3 Ma.PHP moves northwestward and subducts beneath SW Japan at a convergent rate of 4 cm/yr. The Izu-Ogasawara Trench (IT) also moves at the same rate as the westward component (ca. 3 cm/yr.) of the PHP motion. Both the trench-trench-trench (TTT) triple junction and the Japan Trench (JT) should migrate westward, because the thick, cold, and sturdy Pacific Plate (PAP) has never been cut by the transform fault at the TTT junction. Northeast (NE) Japan would also move westward because tectonic erosion along JT would not be sufficient for westward migration of the JT. Thus, the present PHP movement causes the westward migration of IT, TTT junction, JT and then NE Japan. This westward motion of NE Japan against the sturdy oceanic lithosphere of the Japan Sea has caused an E-W contraction of NE Japan since northward motion of PHP changed to NW at 3 Ma.It is expected that rifting of the thin, heated lithosphere of the Izu-Ogasawara Arc would reach break-up before the thick, cold lithosphere of the PAP would be torn by the right-lateral transform fault at the TTT junction. Once rifting reaches break-up, the northwestward movement of the PHP would be compensated by back-arc spreading, and this motion would not propagate to the IT, the JT nor NE Japan. Therefore, the present E-W contraction in Japan would cease in the geologically near future when back-arc rifting along the Izu-Ogasawara arc reaches break-up.McKenzie and Morgan (1969) discussed how the TTT triple junction was unstable except under a few uncommon geometrical and kinematic conditions. However, the PHP actually selected this particular Euler pole position at 15 Ma, and the TTT triple junction had been stable for more than 10 m.y. Although the present TTT junction is in an unstable condition, it would become stable again through back-arc basin spreading of the PHP in the geologically near future. Thus, the TTT triple junction offshore central Japan, which controls tectonics of Japan, would be in a stable state in nature.

著者

横山 又次郎

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.525-527, 1932-10-15 (Released:2010-10-13)

著者

遠藤 毅

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.113, no.6, pp.785-801, 2004-12-25 (Released:2009-11-12)

参考文献数

13

被引用文献数

20 14

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The Tone River which has the largest river basin in Japan rises in Mt. Oominakamiyama in the northern part of Gunma Prefecture. It runs down south to Maebashi City, and changes course to the east, then discharges into the Kashimanada Sea at Choshi City in Chiba Prefecture. It, however, used to flow south near Kurihashi Town in Saitama Prefecture, which lies mid-way between Maebashi and Chosi, and flowed in to Tokyo Bay. This rerouting was achieved by the work of the Tokugawa Bakufu in 1654. Before rerouting, the estuary had been in the northern part of the present Sumida Ward, the eastern part of Tokyo. In the estuary area, which corresponds to the Kohtoh region, consisting of Sumida and Koto Wards and the eastern part of Edogawa Ward at present, the sea was shallow and a lot of sand bars scattered over. The Kohtoh region naturally had favorable conditions for reclamation.When Ieyasu Tokugawa entered Edo Castle in 1590, the environs of the castle were limited, because the east side of the castle faced to an inlet called Hibiya Irie, and the other sides were surrounded by rough plateaus. Topographically the site was good for a fortress but too small to make a town and farming estate. Soon after his settlement, Hibiya Irie was reclaimed to build a town for warriors and citizens, and the Onagi cannel was excavated in the shallow sea which spread on the east of the Edo City for transporting food and salt. The soil dredged from the Onagi channel was used for filling the northern part of the channel. It was the first reclamation work in the Koto sea region. Since then reclaiming works have continued in the Koto sea region, which used to be the estuary of the Tone River. A lot of land has been reclaimed due to garbage disposal in the city since 1655.In the Tokyo Bay area, about 2, 700 ha was had reclaimed during the Edo era period over 270 years, and about 6, 000 ha from Meiji Era to the present over about 140 years. As a result of those reclamation works, the sea area of the Koto region has been replaced by man-made lands, with the exception of some ship routes.

著者

河野 常吉

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.2, no.3, pp.129-131, 1890-03-25 (Released:2010-10-13)

著者

山川 修治

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.102, no.2, pp.183-195, 1993-04-25 (Released:2010-11-18)

参考文献数

60

被引用文献数

1 5

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Natural disasters in Little Ice Age (c. 1550-1850) and its climatic variations which formed a significant background for the disasters are mentioned. Cool summers due to a prevailing Okhotsk High were characteristic of this period. Cold winters, summer heavy rains and unstable atmospheric conditions also constituted essential features of Little Ice Age. Aerosol ejected by a series of major volcanic eruptions partly prevented solar radiation from reaching the earth' s surface (parasol effect), which resulted in cool and unusual weather. Agriculture, in particular, was vulnerable to bad weather damage. As a result of decreasing direct insolation, sometimes together with lowering temperature and/or locally increasing precipitation, seven major famines occurred during the Edo Era (1663-1868) which approximately coincided with Little Ice Age. Several cases in this paper suggest that natural environment in Little Ice Age was marked by both volcanism and weakened solar activities which “Maunder Minimum”(1645-1715) represented.