著者

Koto B.

出版者

東京帝國大學理學部

雑誌

The Journal of the College of Science, Imperial University of Tokyo, Japan

巻号頁・発行日

vol.19, pp.1-61, 1903-04-23

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In recapitulating what has been stated in the foregoing pages, I must first of all say that the geological-structural lines upon which the present paper has been woven, may not be entirely intelligible to the reader without some prefatory geological description accompanied by a geologic map. Some may even cast doubt upon my statements which, of course, must await verification by future observers. In regard to the geology of Korea, I hope I shall be able within a few months to give general outlines with an account of the geological history of the peninsula. Korea is, as I have said, the Italy of Eastern Asia jutting out southward from the main body of Manchuria, just as Italy does from the other end of Eurasia. It is limited on the north by the equatorial chain of Chyang-paik-san which is looked upon by the Koreans as an offshoot of the great Kuen-lun, after being interrupted in its eastward course by the depression of Liau-tung at I-wu-lii-shan. On the southern foot of the Chyang-paik-san range lies the basin of the Am-nok and Tu-man Gang which are separated from each other at Hyoi-san-nyong (700 m.) by a lava-flow from Paik-tu-san, the highest point (8,900 feet) of the Chyang-paik and the cradle of the Korean nation. The Alps and the plain of the river Po are the counterparts of these in the Italian peninsula. They lie nearly in the same latitude, enjoy a favourable climate, and are inhabited by peoples of very ancient culture. The peninsula is divisible on good grounds into two sections-North and South Korea-by a trench, in the geological sense, from the head of Gen-san harbour to Kang-hoa Bay, at one corner of which is located Che-mul-pho, the emporium and entrance to the capital Seoul. This trench or rift-valley is lava-drowned (Pl. I, Fig. 3) and ins the only extensive volcanic field in South Korea, except the large basaltic island of Chyoi-jyu (Quelpart) off the southern coast of Chyol-la Do. This rift-valley or Graben of Chyuk-ka-ryong (510 m.) affords the easiest passage obliquely across the peninsula from the Sea of Japan to the Yellow Sea, and marks the boundary of various geographic elements: a) Historically, North Korea is the land of Old Chyo-syon. The dynasties founded by Tan-gun, Keui-cha, and Ui-man under the name of Chyo-syon, and Ko-ku-ryo or Ku-ryo founded by Chyu-mong, all had their domains mainly in this portion of the peninsula. At a somewhat later time in South Korea sprung up the First Three Hans - Ma-han, Sin-han and Pyon-han, followed by the Second Three Hans of which Sil-la and Paik-chyoi occupied the south, and Ku-ryo only North Korea. From the historical point of view, South Korea is the land of the Hans. b) Climatically, the North is cold while the South is mild; the latter produces the rice, which is the main staple of the country. c) Topographically, the Han-land (South Korea) is hilly, though lofty mountains crown the high coast along the Sea of Japan, slanting gradually westward and disappearing under the shallow, turbid waters of the Yellow Sea. In North Korea we have the two topographic types of the Kai-ma plateau in the north (Figs. 3 and 4.) and the Paleo-Chyo-syon on the south (Fig. 5.), the latter being hilly land of the type of South Korea though on the average considerably lower. Consequently, the land gradually rises towards the east and most of the large rivers, such as the Am-nok, Chhyong-chhyon, Tai-dong, Yoi-syong, Im-jin, Han-gang, Keum-gang and Yong-san-gang empty into the Yellow Sea. d) The physique and temper of the people in both halves differ in no small measures. The peninsula of Korea presents most interesting problems in the arrangement of its mountains and in its underground structure. Professors. F. v. RICHTHOFEN and C. GOTTSCHE have made an attempt at their solution. On my return home from Korea this year, I had the great pleasure of reading SUESS'Antlitz der Erde which was soon followed by RICHTHOFEN'S Geomorphologischen Studien aus Ostasien, I, II, and III. The former author scarcely touches our peninsula, while the latter lets his Tungusic curve pass through the brinks of the East Kan-ma Land as far as to Ho-do (Hoa-do) near Hamheung, and makes the Korean curce start anew from here and go around the outer side of South Korea as far as to the mouth of the Yang-tze-Kiang. The two curves are said to enclose the land that corresponds to the inner Staffelland of the Great Khingan (Hsin-gan) and Taipanshan in China. The peninsula seems to have interested our two masters almost as deeply as it has the political leaders of our times. Let me try to reiterate what has been said in the present paper in regard to the geomorphology of the peninsula. i. Archaean formation composed, as elsewhere, of gneiss-granite, gneiss and mica-schists, is thrown into board, undulating folds on the front side of the peninsula, in the western portion of the Han-land and Paleo-Chyo-syon, becoming steeper as we go south. The axis of folding stretches from S.S.W. to N.N.E., or S.W. to N.E. Two prominent crests of this type are the No-ryong and Chhya-ryong ranges which extend obliquely across Chyol-la Do and Chhyong-chhyon Do. Besides, many small swellings of the crust-surface can be seen in the Paleo-Chyo-syon Land, though deeply hidden under the mask of Paleozonic formation. Nearly half of the area of the peninsula is occupied by holds of this class. These specialized folds should be classed, according to my view, with the Sinian System of South China, as was originally intimated by PUMPELLY. It is a well-known fact that F.v. RICHTHOFEN prolongs his ideal line of the Sinian System to the frame-work of South Japan, a view endorsed by DR. E. NAUMANN, and the late HARADA. L.v. Loczy is, on the other hand, disposed to think that its is the Tching-ling-shan that is prolonged to South Japan through the Hwai Mountains and the mouth of the Yang-tze-Kiang where the Sinian System clings to it (Anschmiegung). But no one knows what became of them after they disappeared in the Tung-hai. The broad belt of the Sinian System which obliquely crosses the Korean peninsula, if extended beyond the Tung-hai, will join with the mountains of South China, to which the same Sinian System was originally given by PUMPELLY. Baron v. RICHTHOFEN'S ideal line runs from South Japan to Fuchou and then goes along the coast of Fokien and Kwang-tung, as is well seen on H. FISCHER'S map of East Asia. As may be seen on any tolerably good map of South China, a greater portion of the Sinian System, of which Ta-yu-ling forms the axis, enters the Tung-hai between Fuchou and Shang-hai, and its further prolongation will correspond well both in its direction and its breadth to those which I venture to call the Sinian folds of Korea. It should be specially remarked that, if the Sinian System in Korea be prolonged to the north-east, a greater part of the folds will again unite directly with the tectonic lines of the Sichota-alin, as they are given in Ivanow's work. (Pages 13-17.) ii. The Sinian represents an old system of crustal folds in the peninsula; and contemporaneously with it or a little later, there was generated another system in the Liau-tung direction in the Kai-ma Land, which was posthumously faulted in serial order towards the south, producing the parallel ridges of Myo-hyang-san, Tyok-yu-ryong and Kal-eung-nyong. These trend from W.S.W. to E.N.E. and form apparently the direct continuation of South Manchuria. The well-known Chyang-paik-san stretches, however, cast and west, obliquely meeting the preceding in the basin of the Tu-man Gang. The upper am-nok Gang drains the acute angled area between the two systems which are cut down crosswise by the Syo-Chyang-paik-san at the north-east coast of Ham-gyong Do. (Page 34.) iii. By the Korean System I mean that complex of uplifted edges and sometimes folds which run more or less in north-south direction along the long axis of the peninsula. It is so characteristic to the physiognomy of the land that even native geographers long before us recognized its great importance in the surface-features of the peninsula. It is also so peculiar to Korea that I know of no other mountains bearing the same trend as these in South-east Asia. I presume, however, that something like the Korean direction may perhaps be looked for beyond the Chyang-paik-0san range in Kirin and also at the terminal portion of the long ridge of the Great Khingan. Also a part of Kyu-shu (Japan) may be within its reach. Within the complex of the Korean System, there seem to exist two natural subgroups which are named respectively the Thai-Paik-san and the Syo-Paik-san. a. The first constitutes the backbone of the peninsula extending from the south-east of Kyong-syang Do toward the N.N.W., along the coast through Thai-Paik-san, O-dai-san and Keum-gang-san. After a short interruption it seems to stretch to Nang-nim in the Kai-ma Land which is separated by it into east and west halves, while at the same time it forms the boundary of Phyong-an and Ham-gyong. A sudden turn of the upper Am-nok, -the Angle of Mao-erh-shan, -is probably due to its prolongation, while the axial trend of Ko-chyoi Island indicates how the mountains curve a little to S.W. on entering the south Korean Archipelago. Five components of the Thai-Paik-san are the cliffs of tilted blocks sweeping along the coast of the Sea of Japan, from which the right wing was successively thrown down to the sea-bottom, as if it originated in disjunctive faults as an after-effect of the piling and pressing up of Hondo (Japan) toward the pacific ocean. (Pages 17-22.) b. The second or Syo-Paik-san subgroup is also composed of fault-scarps which trend south of south-west. This sub-group builds the water-parting and boundary-wall between Kyong-syang on the one side and Chyol-la and Chhyung-chhyong on the other. Instead of maintaining the nearly parallel course of the members of the Thai-Paik-san, the four component-ridges of the Syo-Paik-san diverge from near the pass of Chhyu-phung-nyong in feather form in South Chyol-la Do. In its north-eastern course the Syo-Paik-san is cut off by the Thai-Paik-san, exactly as the fold-crest of No-ryong, already described, which, however, differs slightly in direction and greatly in its structure from the Syo-Paik-san members. (Pages 22-26.) iv. No less remarkable than the preceding is the direction of the Han-san range which chiefly confines itself to the southern border of South Korea. It trends from W.S.W. to E.N.E.; and corresponds well with the north side of South Japan, but as regards its western prolongation it is no easy matter to conjecture what will be its probable continuation. I simply suggest the idea that we might look for its linear extension in the basin-ranges that govern the course of the Lower Yang-tze Kiang. These low ranges seem to belong neither to the Kuen-lun, nor to the Sinian. (Page 31.) The Han-san Range resulted from a later geologic even than that which produced the Korean System. The former is composed of a number of tilted edges of faults which threw down block after block to the Southern Sea. The sea-coast is dotted with an innumerable number of islets and rocks, and describes complicated in-and-out curves. These peculiar features which characterize the coast, are nothing more than the outcome of the joint-work of the orogenic movements that gave form to the Korean and Han-san ranges. The inlets are the remains of tectonic valleys, while the headlands represent the ridges. Especially remarkable is the narrow canal of the free port, Ma-san-pho which presents the outline of a compound cross with a single axis, due to the Korean and Han-san ridges which intersect each other on both sides of the entrance. (pages 26-31.) This is a special form (PI. III, Fig. 2) which truly deserves an independent position in the list of many coast-types. I name this the Nam-hai type as this special kind of coast-line is seen all along the shores of the Nam-hai or South Sea of South Korea. v. A great number of small ridges or fault-scarps traverse like a gridiron the whole of Paleo-Chyo-syon. The region is somewhat similar in its geological structure to the western half of Shan-tung. Well-established rules can be scarcely discovered in the arrangement of ridges. The whole tract is broken up into a number of long orographic blocks, each being of old sedimentaries, mainly of grey tabular limestone. Each block is tiled along the long side with steep walls, while it slants gradually towards the opposite direction. Some of the equatorial ridges may be brought into connection with the tectonic line of Shan-tung, e.g., Myor-ak-san of Hoang-hai Do, while others of the same group are difficult to correlate with any known system. Meridional ridges, though coinciding in direction with some of the Korean System, do not harmonize with each other in position, nor in magnitude of disturbance; the general plan of the west coast, however, seems to have been greatly influenced by them. (Pages 46-50.) In short, the intercrossing fault-scarps of Paleo-Chyo-syon inserted between the Sinian and Liau-tung systems seem to be the result of a passive movement and after-effect of the still greater tectonic disturbances which gave to the crust-block of the Korean peninsula its present form.