Geographical Review of Vol. 63 (Ser. B), No. 1, 73-87, 1990

The Uplands and Lowlands of : A Geomorphological Outline

Sumiko KUBO*

Abstract

Landforms of the main part of Tokyo Metropolis consist of Pleistocene uplands and Holocene lowlands. The original forms of upland surfaces are sea bottoms of the Last Interglacial Age, or the fluvial surface of the Last Glacial. These terrace surfaces are covered with thick air-laid tephra layers. They were supplied by westerly sitting volcanoes such as Mt. Fuji and the Hakone Caldera during the late Pleistocene. The uplands are dissected by valleys whose heads are situated on the up land surface. Some valleys in the upland were formed by remnant streams on the upland surface where tephras were accumulated. The origin of these valleys dates back to the Last Glacial. The lowlands were the places where some large valleys were cut during the Last Glacial. The ma rine deposits of the Postglacial Transgression buried these valleys. Fluvial systems, including the Japan's largest river Tone, developed after that. These deposits formed the "soft ground". The outline of the evolution of Tokyo Lowland during the late Holocene is shown by the method of historical ge omorphology. Since the 17th century, river courses have been changed artificially and the coastal area along has been reclaimed and filled up. The Tokyo Lowland is the most transformed area by human activities in Japan. The characteristics of the mobile belt such as crustal movements and volcanic activities have played as important a role as the ecstatic changes in the landform of the uplands and lowlands of Tokyo. Human activities are increasing on the landform of Tokyo.

Key words: MusashinoUpland, TokyoLowland, upland dissecting valleys, historical geomorphology

developed mainly in the Quaternary (KAIZUKA, I. INTRODUCTION 1987a). For instance, the thickness of Quaternary deposits on the Kanto Plain exceeds 1,500m Tokyo is located in the southern part of the (Research Group for Quaternary Tectonic Map, Kanto Plain in central . The Quaternary 1973); therefore, it is called the Kanto Tectonic systems have developed in the Kanto Plain from Basin. the foot of the Kanto Mountains, which consists Situated in the Kanto Tectonic Basin and also of Palaeozoic and Mesozoic rocks, to Tokyo in Japan's largest river basin of the Tone, the Bay. They form hills, terraces and lowlands (Fig. uplands and lowlands of Tokyo represent a type 1). The main part of the capital city, Tokyo, is of Japanese plains. Furthermore, many volca built on the Pleistocene terraces (diluvial up noes are situated around the Kanto Plain. Vol lands) and Holocene lowlands (alluvial canoes such as Mt. Fuji, Hakone Caldera, Mt. lowlands), just the same as for Osaka and Asama, and so on, have supplied many products Nagoya. to the drainge basins. Tephras facilitate the The characteristics of coastal and fluvial plains stratigraphic investigations in this area. in Japan with thick sediments show marked Glacial eustacy has greatly influenced the for differences from continental erosional plains mation of uplands and lowlands of Tokyo. The (OYA et al., 1988). The sediments deposition is sea level change caused to form terraces, valleys strongly connected with crustal movements and plains. The Tokyo Lowland is the latest sur which make mountains and basins. They have face to emerge from the Holocene transgression.

* School of Education, Waseda University, Nishi-Waseda, Shinjuku-ku, Tokyo 169 74 S. KUBO

Figure 1. Study area (revised after KAIZUKA, 1987b)1 : mountain,2: volcano,3: hill, 4: upland,5: lowland,6: centerof subsidence,AL: ArakawaLowland, NL: NakagawaLowland, TL: Tokyo Lowland.

Since it emerged, this area has been inhabited in lands during the historic ages. No comprehen the Late Holocene. sive studies have been done about the paleo The environmental conditions of the Tokyo landforms in the late Holocene, however. Lowland in the historic and prehistoric ages are The main part of Tokyo (23 Wards) developed almost unknown. It once was a sea bottom in around a former castle which was built on the the age of 6,000yBP. After that sea level lowered rim of the uplands in 1457. From 1603 to 1867 several meters and fluvial deposits have covered the TOKUGAWAshoguns used this topographic the lowland surface where we live on. The sea condition effectively for protection of the castle level fluctuations have given changes to coast and the castle town of . After the lines. Moreover, fluvial deposits have formed Restoration in 1868, the former Edo city was The Uplands and Lowlands of Tokyo 75

changed into the new capital Tokyo. Since the gives us more information in order to know why establishment of the city, people in Edo and the present landform exists here. The distribu Tokyo have changed their natural environments tion and evolution of the uplands and lowlands significantly for flood control, cultivation, habi of Tokyo are an important knowledge for the tation and so on, especially in the lowland. Hu foundation of Tokyo. man activity is becoming a more and more important factor for landforms in Tokyo. II. LANDFORMS OF THE UPLANDS Comparing with the sedimentary or strati 1. Previous studies on the uplands graphic studies, fewer studies have been made on landform itself (e.g., shapes and distribution Many have studied the geology of the uplands of uplands, rivers, valleys and some small topog in the Kanto Plain. They described the Pleisto raphies). Geomorphological approaches have cene marine and fluvial deposits covered with the "Kanto Loam" been done mainly from the viewpoints of land , which is a fine-grained deposit form evolution and geomorphological process like loess. The Kanto Loam Research Group es in connection with geology. On the other (1965) defined it as "volcanic ash layer of the hand, the approach focused on landform relief Pleistocene in the Kanto district", and estab

Figure 2. Chronology of terrace surfaces in the Musashino Upland (revised after Research Group for Geology and Geomorphology of Sagami hara City, 1986) 1: buried soil, 2: volcanicash, 3: scoria,4: pumice 76 S . KUBO lished the comprehensive stratigraphy and rela supplied from the westerly located volcanoes tions with the terraces or the archeologic such as Mt. Fuji and Hakone Caldera. Total horizons. thickness of the tephra layers increases toward Recent studies on the upland area have ad the volcanoes. Tephra layers have some key beds: vanced on the basis of the Kanto Loam Research extinct pumice beds, vitric ashes and some bu Group (1965), in relation to the glacial eustacy, ried soil layers. They made it possible to divide tephrochronology and other Quaternary studies surfaces into more details by both stratigraphy (MACHIDA,1973; 1975, KAIZUKA,1979, etc.). and differences in tephra thickness. Figure 2 The following are the simplified results: shows some absolute ages of key beds which were The upland surfaces are covered with thick obtained by the fission-track and radiocarbon "Kanto Loam" or air -laid tephras. They were datings. These ages show that tephras have been

Figure 3. Valleys "dissecting" the Musashino Upland (KuBo, 1988a) 1-3: classificationof valley types (see text); 4: JR Line,S: Shimosueyoshi Surface, M1, M2: Musashino Surfaces, Tc: TachikawaSurface The Uplands and Lowlands of Tokyo 77

supplied constantly by many intermittent erup These small valleys are said to be developed af tions rather than by a few large eruptions in a ter the upland surface emerged. However, this short duration which make key beds. The rate idea needs to be revised because tephra deposi of tephra deposition is estimated to be 1m per tion has taken place on the upland surfaces while 10,000 years around Tokyo, although it becomes they have been dissected by valleys. Therefore, larger toward west. the evolution of these valleys should be under Tokyo develops on the Musashino Upland, stood as a result of these reciprocal processes: consisting of S (Shimosueyoshi), M (Musashino) stream erosion and tephra deposition. and Tc (Tachikawa) Surfaces. The S Surface in KUBO (1988a) explained the evolution of these the main part of Tokyo was formed as a shal valleys under the conditions mentioned above. low sea bottom during the Last Interglacial According to this study, the longitudinal profiles (130-120ka); so that the surfaces are those of of valleys dissecting the Musashino Upland such marine terraces. The M and Tc Surfaces are flu as the Kanda, Meguro and Sen river valleys, can vial surfaces formed during the Last Glacial be divided into upper, middle and lower seg (80-13ka). The altitude of this upland is about ments (Figs. 3 and 4). 20-30m at the eastern edges. They are classi The upper segment with a gentler gradient is fied more precisely into M1, M2, M3, Tc1, Tc2 named here type 1 valley. The longitudinal pro and Tc3 as shown in Figure 2. file of this segment runs parallel with the project 2. Geomorphological features and the origin ed upland surface. Type 1 valleys sometimes of valleys in the Musashino Upland show meandering forms. In such meandering valleys, streams also meander. The wavelength The Musashino Upland is dissected by many of valley meander is, however, far greater than small valleys such as the Shakujii, Kanda, that of stream channels, by about 10 times. The Meguro and river valleys (Fig. 3). Their middle segment, type 2 valley, have a steeper gra valley heads are situated on the upland surface. dient than others. It is bordered by knickpoints.

Figure 4. Longitudinal section along the Valley (KUBO, 1988b) 78 S. KUBO

The slope seems to continue to the bottom of re reach. 3) The valley bottom stands along the top cent deposits which buries the valley formed dur of gravel layers. 4) The wavelength of valley ing the Last Glacial. The lower segment, type 3 meander is far larger than that of stream chan valley, has a gentle gradient because of the depo nels in the valley. KUBO(1988a) assumed for the sition during the Holocene transgression. evolution of these valleys from these features as There are some common features among the follows: a "remnant stream" on the upland sur valleys of the Musashino Upland as follows: 1) face formed a valley by flowing tephras away The valleys dissect the upland which consists of along the stream channel, succeeding to the Pleistocene terrace gravel layers and thick air former river course. In other words, some val laid tephras. 2) The plane forms of valleys are leys in the Musashino Upland can reasonably be consequent to the upland slope direction and interpreted as having been formed by the have few tributaries. The width of these gutter removal of tephras along the former river shaped valleys is uniform throughout the entire courses.

Figure 5. Model showing the evolution of vallyes (KUBO, 1988a) 1: tephra, 2: gravel The Uplands and Lowlands of Tokyo 79

Figure 5 shows the model of evolution of these Geologists and geomorphologists have discussed valleys: 1) A former river course remains on a the geological history of late Pleistocene and terrace surface. 2) Remnant streams flow away Holocene on the basis of the stratigraphy and bu falling tephras along the former river course. 3) ried landforms (HATORI et al., 1962; MATSUDA, Tephras accumulated on both sides of the stream 1974; KAIZUKAet al., 1977, ENDO et al., 1982, form a "valley". and so on). These features are not seen in the marine-origin The stratigraphy of the deposits in Tokyo is S Terraces, Yodobashi and Ebara Uplands. These compiled as Fig. 6. The uppermost part of the terraces consist of shallow sea deposits of fine Tokyo Lowland is occupied by the artificial fills materials, and have small surface gradients and the rubbishes of World War II, large earth (KUBO, 1990). quakes and fires. Under this layer is the Yurakucho Formation mainly consists of loose III. LANDFORMS IN THE LOWLANDS sand in the upper part and very soft clay containing shells in the lower. These are the 1. Previous studies on the stratigraphy and Holocene deposits under which Pleistocene ter buried landforms in the Tokyo Lowland races and valleys are buried. In 1923, the Great Kanto Earthquake (M=7.9) Figure 7 shows the buried landforms of the attacked Tokyo and killed more than 100,000 Tokyo Lowland (MATSUDA, 1974). Two large people. The disaster was especially severe in the valleys stretch to different directions: the Paleo lowland area. After that the Reconstruction Arakawa Valley in the northwest and the Paleo Bureau (1929) made many bore holes to inves Nakagawa Valley in the north. They join in the tigate subsurfce geology. Since then the geolog Tokyo Lowland and form the "Paleo Tokyo ical knowledge of lowland area has increased Valley". The sea level corresponding to the bot with bore-hole data investigations. Recently, the tom of the Paleo Tokyo Valley is estimated to Institute of Civil Engineering of the Tokyo be lower than -100m. The buried terraces a dis Metropolitan Government (1969, 1977) compiled tributed along these two valleys. They contain records of many bore holes for constructions. both abrasion platforms and river, terraces.

Figure 6. Simplified geological cross-section of Tokyo (Inst. of Civil Engineer., Tokyo Met., 1977) 80 S . KUBO

ly done with stratigraphic aspects. Although it is the youngest landform, knowledges about the landforms developed in the recent 6,000 years are not enough at all. In this respect, it is to be not ed that KAIZUKA(1979) described that the coast line of 2,000yBP lied along the boundary of the Nakagawa Lowland and the Tokyo Lowland. The stratigraphic method is hardly applicable to the explanation of such geographical problems: how regression occurred and lowlands developed in the late Holocene. Micro-landforms on the lowland surface are expected to give usable data for considering these problems. Geomorphological land classification maps of Tokyo and its vicinity have been made mainly by governmental offices for disaster mitigation including floods and ground damage caused by earthquakes (e.g., Geographical Survey Institute, 1982). The original land condition before intense urbanization is shown by OYA and HARUYAMA

Figure 7. Distribution of the buried landforms (MA (1988) for Katsushika Ward, a part of the Tokyo TSUDA, 1974) Lowland. This map expresses micro-landforms 1: upland, 2-5: buriedterraces, 6-9: buried abrasionplatforms , 10: based on the interpretation of airphotos of the buried valleyfloor 1940's. They estimated flood damage by this map. These maps aimed to show the ground con ditions of now and the future, rather than histor Recently, detailed studies utilizing microfossils ic background. such as pollen, diatoms and foraminifers in the This study intends to estimate the landforms Holocene deposits have progressed. They urge in the historic and prehistoric times utilizing a to reconstruct the depositional environments and geomorphological land classification map. The to clarify the Holocene stratigraphy in detail author prepared a geomorphological map of the (e.g., ANDO et al., 1987; ENDO et al., 1988 and whole Tokyo Lowland (Fig. 8). In general, the KOSUGI, 1989). Nevertheless, still further studies Nakagawa and Arakawa Lowlands are of com covering the whole Tokyo Lowland should be ex binations of natural levees and back marshes; the pected. Tokyo Lowland is a deltaic area including artifi In the Tokyo Lowland some large valleys were cially land fills. Low ridges where older settle formed during the Last Glacial, and buried with ments located are distributed throughout the marine and fluvial deposits which were related Tokyo Lowland. They are classified into three to the Postglacial Transgression. Transgression groups: 1) a group of low ridges distributed along invaded inland about 50km from the recent coast the upland rims, 2) those along the major rivers in about 6,000yBP. The unconsolidated sand or former major rivers flowing from north to and clay layers were deposited in this Inner south, and 3) a group of ridges stretches west to Tokyo Bay. Attention has been paid to this "soft east. The first group sometimes choke up the ground" in relation with earthquake damage and mouths of dissecting valleys of uplands and is ground subsidence (NAKANOet al., 1969; KAizu estimated as having been sand bars. Second was KA, 1979). natural levees, while the last was sometimes the former and sometimes the latter. These low 2. The method for landform reconstruction ridges and other micro-landforms show the dis in the historic and prehistoric times tribution of former rivers and coastlines. Based Geomorphological studies on Tokyo are main on this geomorphological map, archeological The Uplands and Lowlands of Tokyo 81

Figure 8. Distribution of low ridges in the Tokyo Lowland1 : natural levee, 2: sand bar and historical data were inspected and then used Tone, however, does not flow through the Tokyo for chronology of landforms. Lowland now. It flows into the Pacific Ocean directly via the Kinu River, connected by a canal 3. Landform transformation by the human which was constructed in the 17th century. The activities in the Tokyo Lowland former flowed in the course of the The Tokyo Lowland was created by the Tone Naka River before the 17th century when system, one of the largest in Japan. The was established. 82 S . KUBO

The whole river system in the lower Tone, in da) connected the Tone and the Sumida. Sepa cluding the Ara, the Edo and the Kinu, was ar rated from the Tone, the Ara was given its course tificially changed first in the 17th century. The in a lowland to the west of the Omiya Upland former Ara River flowed along the eastern side so as to be connected with the of the Omiya Upland and drained into the Naka which drained into Tokyo Bay. The upper reach River (Old Tone). The Furu-Sumida (Old Sumi of the Edo River, however, was connected with

Figure 9. Artificial transformation of landforms in the Tokyo Lowland The Uplands and Lowlands of Tokyo 83 the Tone to become a distributary. Many irriga drainage system in the Tokyo Lowland has be tion and drainage canals were made mainly af come very complex by human activities. ter the 17th century (KOIDE, 1975). In the 20th The reclamation of Tokyo Bay has long taken century, the floodways of the Ara, Edo and place since the 17th century, particularly in the Naka Rivers were excavated. In this way, the area between the Sumida and Edo Rivers. The

Figure 10. Distribution of sites and the estimated landform of the Middle Ages (KuBo , 1989) 1: upland, 2: naturallevee, 3: sand bar, 4: tidal flat and marsh, 5: recentriver and coast, 6: Jomonpottery (10,000-2,300yBP),7: Yayoi pottery (300B.C.-300AD.), 8: Kofuntomb (4-6th century),9: Haji and Sue potteries(4-9th century), 10:after Haji, 11:JR Line 84 S. KUBO back marsh areas of the Nakagawa lowland were deposition of the so-called "black clay" in the drained by canals and converted to paddy fields Tokyo Lowland. It is possible to correlate the (Resources Bureau, 1961). After World War II, spread of brackish water with the transgression land filling advanced extremely rapidly along the of the 4-12th centuries (ISEKI, 1983). The Tokyo Bay coasts (Fig. 9). transgression might have caused these marshy According to the industrialization of Tokyo, lands in inland areas. ground subsidence was accelerated by over 5. Former landforms from historical data pumping of groundwater. Ground subsidence and geomorphological land classification recorded a maximum of 4m during these 60 years maps and created a broad "below sea-level areas" in the Tokyo Lowland (NAKAGAWAet al., 1969). The earliest historical description of the Tokyo To consider the landform in prehistoric and Lowland comes from the 7th century, the estab historic times, the original landform without ar lishment of the Sensoji Temple on the tificial transformation is required. Figure 10 is sand bar besides the Sumida River (Sumida the estimated topographic map of the Middle Ward, 1978). The famous ancient "Man'yo Ages (16th century), which shows the original shu" verses edited in the 8th century mentions landforms of the Tokyo Lowland. the Mama Lagoon. This can be correlated with the valley plain still called Mama behind the 4. Former landforms and archeological sites Ichikawa sand bar. An oldest population record Figure 10 also shows the distribution of archeo in Japan for Katsushika District of the Shimou logical sites and their relation to landforms sa Province here describes two village names, (KUBO, 1989). Back marshes were well deve Kowa and Shimamata. The two can be correlat loped in the upper reach of the Lower Tone ed with the modern Koiwa and Shibamata River, while the did not have many. (Edogawa Ward, 1976), located on a sand bar The Tone trifurcated its distributaries into the and a natural levee, respectively. Furu-Sumida/Sumida, Naka and the Edo River In the 8th to 9th century, the provinces in the Tokyo Lowland. The western branch was Musashi and Shimousa were separated by the joined with the Iruma River to form the Sumida Furu-Sumida and the Sumida Rivers, which in the lower reach, while the eastern branch, the probably was a main trunk of the lower Tone Edo, with the Futoi. Thus, the whole area of the River. In the 12th century, boats were used to Tokyo Lowland was subjected to frequent floods go to the Musashino Upland from the right bank of the Tone. of the Sumida River. This means the existence Archeological sites of the Jomon to Yayoi Peri of a water area between the Sumida R. and the ods (about 10,000B.C. to 100A.D.) are not Musashino Upland (SUZUKI, 1975). In this area, numerous in the Tokyo Lowland. Sites of the late there was a broad wetland or a marsh named Yayoi to Kofun Periods (100A.D, to the 6th cen Senzoku-ike Pond or Himega-ike Pond in the tury) are concentrated on the low ridges along 15th century (Sumida Ward, 1978). the Kenaga and in the middle of the lowland. These descriptions suggest that 1) early settle ISEKI(1983) describes that the sand bars along ments were located on the natural levees and the Kenaga and the Ichikawa area are old in ori sand bars, 2) a major branch of the Tone River gin, about 4,000 and 6,000yBP, respectively. Bu flowed through the Sumida via the Furu-Sumida ried abrasion platforms are distributed along the and made the border between Musashi and Kenaga and Edo Rivers (see Fig. 7). Shimousa Provinces, 3) lagoons and marshy A site located at the southern side of the lands were often seen in the inland area, and 4) Ichikawa sand bar shows the former coastline the coastline ran far north from that of recent during the Kofun Period (6th century). Remain times. ing stilts and a shell mound were discovered in From the above-mentioned facts the author a marshy area (Ichikawa City, 1971). The mar concludes that the areas along the Kenaga, Edo shy environment there is estimated to date back and Naka Rivers were inhabited very early. These to the Kofun Period (4-6th century) with the areas emerged earlier because of the existence of The Uplands and Lowlands of Tokyo 85 higher abrasion platforms and deposits of the also in prehistorical and historical times. Using former Tone and Kenaga (probably the former the method of the historical geomorphology, Ara). On the other hand, the areas between the former landforms were reconstructed, in that a Musashino Upland and the Naka River and the small transgression in the historic times is southern side of the Shimousa Upland remained thought to have sunk some areas and how hu as lagoons or ponds even in the Middle Ages. man activities have transformed the area. These facts may suggest a small transgression in The crustal movements, volcanic activities and the historical times. Back marshes in the Nakaga sea level change representatively show the geo wa Lowland and former lagoons in the Tokyo logical and geographical settings of Japanese Lowland were drained, reclaimed and filled up plains. The environment of Tokyo has been artificially (KUBO, 1989). changed not only by the physical conditions produced in the global scale but also by humans. IV. CONCLUSIONS AND Because of cultivation, urbanization and indus SOME FURTHER PROBLEMS trialization, the environment of Tokyo has been changed more and more. Natural disasters The landform of Tokyo was formed in rela caused by earthquakes and floods are also affect tion with the Quaternary history and the geolog ed by the environmental and social change (OYA ical and geographical settings of Japan. On the and HARUYAMA,1989). Historical geomorphol global scale, the Japan Arc is located in a colli ogy is thought to be able to consider the environ sion area of plates. Furthermore, the Kanto Plain mental change during prehistorical and historical is the only place where three plates collide with times effectively. (NAM, EUR and PHS). The movement form (Received Oct. 31, 1989) ing the Kanto-Tectonic Basin transforms its up (Accepted Jan. 31, 1990) land surfaces. The two centers of subsidence are shown by transformation of the S Surface

(KAIZUKA, 1987a, b). Acknowledgements Many volcanic products covered and raised the uplands higher. They buried and kept some I am grateful to Dr. Masahiko OYA, Waseda Univer materials which indicate the former environ sity, for his continued support and suggestions. I also ments. Tephra deposition made some relief as would like to thank Dr. Sohei KAIZUKAand Dr. Hiroshi valleys in uplands. They were formed during the MACHIDA, Professors of the Tokyo Metropolitan Pleistocene due to tephra deposition, except University, for their supervisions of the upland studies. This study was supported by a Waseda University Grant along the remnant streams. The surface of the for Special Research Projects, 1989. Kanto Plain would be lower and more flat if tephras did not exist. Volcanic activities have also affected the References lowlands. For instance, the eruption of the Asa ma Volcano in 1783 supplied much volcanic ANDO, K., WADA, M. and TAKANO, T. (1987): On materials into the Tone River basin and caused paleo-environments based on the diatom assemblages fl oods in the lower reaches containing the Tokyo in the Arakawa Lowland, . The Lowland. Volcanic effects on the drainge basin Quaternary Research (Daiyonki Kenkyu), 26, are an important problem to be investigated 111-127. (JE) where there are many active volcanoes. Edogawa Ward (1976): Edogawa-kushi (History of Edogawa Ward), Vol. 1, Edogawa Ward, Tokyo, 942 In the Last Glacial, no glacial relief was seen p. (J) in the drainage basin of the Tokyo Lowland. On ENDO, K., SEKIMOTO,K. and TAKANO,T. (1982): Holo the other hand, the glacial eustacy had a great cene stratigraphy and paleo-environments in the Kan influence on the landforms in Tokyo. The Tokyo to Plain, in relation to the Jomon Transgression. Proc. Inst. Natural Sciences, College of Humanities and Lowland has been constructed by the deposits Sciences. Nihon Univ., No. 17, 1-16. (E) of Holocene transgression and the Tone River ENDO, K., KOSUGI, M. and HISHIDA, R. (1988): Holo system. The form of this area has been changed cene and Late Pleistocene deposits and basal topogra 86 S. KUBO

phy in the Kanto Plain, Central Japan. Proc. Inst. MACHIDA,H. (1975): Pleistocene sea level of South Kan Natural Sciences, College of Humanities and Sciences, to, Japan, analyzed by tephrochronology. In R. P. Nihon Univ., No. 23, 37-48. (JE) SUGGATE,M. M. CRESSWELLeds: Quaternary Studies, Geographical Survey Institute, Ministry of Construction The Royal Society of New Zealand, Wellington, (1982): Tochi joken chosa hokokusho (Report of the 215-222. (E) land condition surveys), Tokyo Area. 106 p, with 4 MATSUDA, I. (1974): Distribution of the recent deposits Land Condition Maps (1:25,000). (J) and buried landf orms in the Kanto Lowland, Central HATORI, K., INOKUCHI,M., KAIZUKA, S., NARUSE, Y., Japan. Geographical Rep., Tokyo Metropolitan Univ., SUGIMURA,A. and TOYA, H. (1962): Latest Quater No. 9, 1-36. (E) nary features of Tokyo Bay and its environs. The NAKANO, T., KADOMURA,H, and MATSUDA,I. (1969): Quaternary Research (Daiyonki Kenkyu), 2, 69 90. Land subsidence in the Tokyo lowland. Geographical (JE) Rep., Tokyo Metropolitan Univ., No. 4, 33-42. (E) Ichikawa City (1971): Ichikawa shishi (History of Ichika OYA, M., NAKAYAMA, M. and TAKAGI, I. (1988): wa City), Vol. 1, Ichikawa City, Chiba Pref. (J) Studies on the geomorphological features of the flu ISEKI, H. (1983): Chuseki heiya (Alluvial Plains). Univ. vial plains in Japan, focusing the distribution, geomor of Tokyo Press, Tokyo, 145 p. (J) pological land classification and its application. KAIZUKA, S. (1979): Tokyo no shizen shi (The natural Geographical Rev. Japan, 61B, 35-49. (E) history of Tokyo), 2nd edition. Kinokuniya-shoten, OYA, M. and HARUYAMA,S. (1988): Geomorphological Tokyo, 239 p. (J) land classification map of the Katsushika Ward KAIZUKA, S. (1987a): Quaternary morphogenesis and (Tokyo) and its vicinity. Board of Education, Katsushi tectogenesis of Japan. Zeitschrift fur Geomorphologie, ka Ward, Tokyo. (E &J) N. F. Suppl. -Bd. 63, 61-73. (E) OYA, M, and HARUYAMA,S. (1989): Flooding and ur KAIZUKA, S. (1987b): Quaternary crustal movements in banization in the lowlands of Tokyo and vicinity. Kanto, Japan. Journal of Geography (Chigaku Zas Natural Disaster Science, Vol. 9, No. 2, 1-21. (E) shi), 96, 223 -240. (JE) Reconstruction Bureau (1929): Tokyo oyobi KAIZUKA, S., NARUSE, Y. and MATSUDA, I. (1977): Re chishitsu chosa hokoku (Geological research in and cent formations and their basal topography in and around the cities of Tokyo and Yokohama). 144 p. around Tokyo Bay. Quaternary Research, 8, pp. Tokyo (J) 32-50. (E) Research Group for Geology and Geomorphology of the Kanto Loam Research Group (1965): The Kanto Loam. Sagamihara City (1986): Sagamihara no chikei, chishit Shokan, Tokyo, 378 p. (JE) su (Report on the geology and geomorphology of the KOIDE, H. (1975): Tonegawa to Yodogawa (The Tone Sagamihara), No. 3. Board of Education, Sagamihara and Yodo Rivers). Chuo Koron-sha, Tokyo, 220 p. (J) City, Kanagawa Pref., 96 p. (J) KOSUGI, M. (1989): Coastline and adjacent environ Research Group for Quaternary Tectonic Map (1973): ments of the former Tokyo Bay in the Holocene. Ge Explanatory text of the Quarternary tectonic map of ographical Rev. Japan, 62A, 359-374. (JE) Japan. National Research Center for Disaster Preven KUBO, S. (1988a): Geomorphological features of valleys tion, Tokyo, 167 p. (JE) "dissecting" the diluvial uplands of Sagamino and Resources Bureau, Science and Technology Agency Musashino, Kanto Plain: A study of valleys formed (1961): Nakagawa ryuiki teishitchi no chikeibunrui to by remnant streams and air-laid tephra. Geographi tochi riyo (Geomorphological land classificaiion and cal Rev. Japan, 61A, 25-48. (JE) land use in the lowland of the Nakagawa River Ba KUBO, S. (1988b): Some geomorphological features of sin). 140 p. (J) Kanda River valley around Waseda University, Tokyo. Sumida Ward (1978): Sumida-kushi (History of Sumida Gakujutsu Kenkyu, No. 37, 57-73, School of Edu Ward), Zenshi (Early history). Sumida Ward, Tokyo. cation, Waseda University, Tokyo. (J) (J) KUBO, S. (1989): Geomorphological changes of the SUZUKI,M. (1975): Edo to Edojo (Edo and the Edo Cas Tokyo Lowland after the Holocene transgression. tle). Shin-jinbutsu-orai-sha, Tokyo. (J) Gakujutsu Kenkyu, No. 38, 75-92. (J) The Institute of Civil Engineering of the Tokyo KUBO, S. (1990): Geomorphological features of valleys Metropolitan Government (1969): Tokyo-to jiban dissecting the uplands of the Kanto Plain. Geographical chishitsu-zu (Geological map of the ground of Tokyo). Reports, Tokyo Metropolitan Univ., No. 25 (in press). (J) (E) The Institute of Civil Engineering of the Tokyo MACHIDA, H. (1973): Tephrochronology of coastal ter Metropolitan Government (1977): Tokyo-to sogo races and their tectonic deformation in South Kanto. jiban-zu (A comprehensive ground map of Tokyo). Journal of Geograhy (Chigaku Zasshi), 82, 53-76. Giho-do, Tokyo, 210 p. (J) (JE) The Uplands and Lowlands of Tokyo 87

東 京 の 台 地 と 低 地

久 保 純 子*

東京首部の地形は更新世の台地と完新世の低地とから もの で,厚 い軟 弱 地 盤 を形 成 す る。 完 新 世 後 期 の 東 京低 なっている。台地は最終間氷期の海底面と最終氷期の河 地 の形 成 過 程 は,従 来 ほ とん ど行 なわ れ な か った 考 古 歴 成面に由来 し,そ の表面は後期更新世を通じて富士火山 史 資 料 と微地 形 分 布 との 関 係 の検 討 に よ り明 らか に され ・箱根火山などにより供給された風成テフラに覆われて る で あ ろ う。17世 紀 以 降 に な る と,河 道 の 改 修,海 岸 部 いる。台地には台地上に水源をもつ開析谷が分布する。 の埋 め立 て等 の人 工 改 変 が大 規 模 に行 なわ る よ うにな っ これらの谷のなかには,台 地表面の離水時に現われた名 た 。 残川に由来し,そ の起源が最終氷期 まで遡 る ものが あ 東 京 の台 地 と低地 の地 形 には,変 動 帯 の 特 色 と して の る。 関 東 造 盆 地 運 動 や火 山活 動 に 加 え,ユ ー ス タ テ ィ ックな 低地は最終氷期末に形成 された谷 が 後氷期海進 を 受 海 水 準 変動 の影 響 が あ らわ れ て い る。 そ して 近 年 は 人 類 け,日 本有数の大河である利根川水系により形成された に よる改 変 が最 も大 き な フ ァ クタ ー とな って い る。

* 〒169東 京 都 新 宿 区 西 早 稲 田 早 稲 田 大 学 教 育 学 部