The Origin of Continents and Oceans/Chapter 4

by Alfred Wegener

CHAPTER IV

GEOLOGICAL ARGUMENTS

A very sharp control on our supposition that the Atlantic is formed of an enormously expanded rift, the margins of which formerly directly adjoined each other, is exercised by a comparison of the geological structures on both sides; for it is to be expected that folds and other structures, formed before the separation, will be continuous from one side to the other, and their terminations on both sides of the ocean must lie exactly in such a position that they appear as immediate continuations in the reconstruction. Since the reconstruction itself is a very restricted one, on account of the well-marked course of the continental margins, and leaves no room for adjustment to fit this requirement, we are dealing with a quite independent criterion which is of the greatest value for the estimation of the accuracy of the displacement theory.

The Atlantic rift is broadest in the south, where it first broke open. Its width amounts here to 6220 km. Between Cape San Roque and the Cameroons there are 4880 km., between Newfoundland Bank and the British shelf 2410 km., between Scoresby Sound and Hammerfest but 1300 km., and between the margins of the shelves of North-East Greenland and Spitsbergen probably only from 200 to 300 km. Here the split appears to have taken place in quite recent times.

Let us commence the comparison in the south. In the extreme south of Africa we find a Permian folded mountain range striking from east to west (the Zwarte Berge). In the reconstruction the westward extension of this range strikes the district south of Buenos Aires, where the map shows nothing remarkable. Now it is an extremely interesting fact that Keidel has discovered in the sierras of this area, especially the more strongly folded southern portion, ancient folds, which from the structure, the succession of rocks and the fossil contents, are not merely absolutely similar to the Pre-Cordilleras on the north-west in the provinces of San Juan and Mendoza, which immediately adjoin the Andean folding, but above all also to the Cape Mountains of South Africa. “In the Sierras of the Province of Buenos Aires, especially in the southern ranges, we find a succession of strata which is very similar to that in the Cape Mountains of South Africa. Good agreement appears to exist in at least three beds: the lower sandstone of the Lower Devonian transgression, the fossiliferous shales which show the maximum of its extension, and a more recent, very characteristic formation, the glacial conglomerate of the Upper Palæozoic. The deposits of the Devonian transgression, as well as the glacial conglomerate, are greatly folded, as in the Cape Mountains, and the movement here, as there, is directed towards the north.”^[1] From this the existence is proved of a lengthy ancient fold which cuts the southern point of Africa and then passes into South America south of Buenos Aires, finally turning northwards to combine with the course of the Andes. The broken pieces of this fold are separated from one another to-day by a uniform ocean floor of more than 6,000 km. In our reconstruction, which allows of no adjustments, the pieces are brought exactly into contact; their distances from Cape San Roque and the Cameroons respectively are exactly the same.^[2] This evidence of the accuracy of the combination is very striking, and reminds me of the use of a visiting-card torn into two for future recognition. The agreement is only slightly affected by the fact that on reaching the coast the range of the Cedar Berge branches to the north, away from the South African strike. This branch, which soon disappears, bears the character of a local deflection, which might well have been caused by a discontinuity at the place where the rift took place later. Such branches are seen to a still greater extent in the European folded mountain systems, both in those of the Carboniferous and in those of the Tertiary, and do not prevent us from combining them in one system and referring them to the same cause. Also, if the African folding has continued into later times, as appears from recent studies, no difference in age can be inferred; for we learn from Keidel: “In the Sierras, the glacial conglomerate, the latest formation, is folded; in the Cape Mountains the Ecca beds at the base of the Gondwana series (Karroo Beds) also show traces of the movements. In both areas the chief movements may therefore have taken place in the interval between the Permian and the Lower Cretaceous.”

But this confirmation of the correctness of our views by the Cape Mountains and their extension in the Sierras of Buenos Aires, is by no means the only one, since we find numerous other proofs along the coasts of the Atlantic. The immense gneissic plateau of Africa, which has not been folded for a very long period of time, shows a striking similarity to that of Brazil. That this similarity is not only confined to broad characters is at once shown by the agreement of the igneous rocks and sediments, and also that of the ancient directions of folding on both sides of the ocean.

The igneous rocks were first briefly compared by H. A. Brouwer.^[3] He found no fewer than five parallels, namely, (1) the older granite, (2) the more recent granite, (3) alkaline rocks, (4) Jurassic volcanic rocks and intrusive dolerite, (5) kimberlite, alnöite, etc. In Brazil the older granite forms part of the so-called “Brazilian Complex,” and in Africa of the “Fundamental Complex” of South-West Africa, the Malmesbury System of the South of Cape Colony, and the “Swaziland System” of the Transvaal and Rhodesia. “The east coast of Brazil in the Serra do Mar, as well as the opposite west coast of South and Central Africa, consist for the greater part of these rocks, and they bestow a similar topographical character on the landscape in both continents.” The younger granite is intrusive into the Minas Series of Brazil in the provinces of Minas Geraes and Goyaz, where it yields auriferous veins, as well as in the province of São Paulo. In Africa, the Erongo granite in the land of the Hereros and the Brandberg granite in the north-western portion of Damaraland correspond to it, as well as the granites of the “Bushveld Igneous Complex” in the Transvaal. The alkaline rocks are found exactly on the corresponding stretches of coast: on the Brazilian side, at different places in the Serra do Mar (Itatiaya, Serra do Gericino near Rio de Janeiro, Serra de Tingua, Cabo Frio); on the African side, on the coast of Lüderitzland, near Cape Cross north of Svakopmund, and again in Angola. At a greater distance from the coast, each with a diameter of about 30 km., are the eruptive regions of Poços de Caldas in the south of the province of Minas Geraes and of Pilandsberg in the Rustenburg district of the Transvaal. These alkaline rocks are very striking in the absolutely similar development of the plutonic, dyke, and volcanic facies. Brouwer says in reference to the fourth group (Jurassic volcanic rocks and intrusive dolerite): “Just as in South Africa, a thick series of volcanic rocks is developed in the lowest portion of the Santa Catharina System, corresponding approximately to the South African Karoo System; these can be considered as Jurassic in age, and cover large areas in the provinces of Rio Grande do Sul, Santa Catharina, Parana, São Paulo and Matto Grosso, and even in Argentina, Uruguay and Paraguay.” Here, in Africa, belongs the Kaoko Formation developed between the latitudes of 18° and 21° S., which corresponds to the similar rocks in the provinces of Santa Catharina and Rio Grande do Sul of Southern Brazil. Finally, the last rock group (kimberlite, alnöite, etc.) is very well known, since its members yield the matrix in which diamonds are to be found, in Brazil as well as South Africa. In both areas the peculiar form of deposits known as “pipes” occurs. “White” diamonds only occur in the province of Minas Geraes in Brazil and in South Africa only north of the Orange River. But, more clearly than in these rare occurrences of diamonds, the agreement is shown in the distribution of the kimberlite matrix. This has also been recognized in dykes in the province of Rio de Janeiro. “Like the kimberlite rocks near the west coast of South Africa, those known from Brazil practically all belong to the basaltic varieties poor in mica.”

But Brouwer also emphasizes the fact that the sedimentary rocks on both sides show a great correspondence. “The similarity between some groups of sedimentary rocks on both sides of the Atlantic is equally remarkable. We need only mention the South African Karoo System and the Santa Catharina System of Brazil. The Orleans conglomerate in Santa Catharina and Rio Grande do Sul corresponds to the Dwyka conglomerate of South Africa, and in both continents the uppermost portions are formed by an already well-known thick series of volcanic rocks, as those of the Drakensberg in Cape Colony and those of the Serra Geral in Rio Grande do Sul.”

According to du Toit,^[4] it even appears as if the Permo-Carboniferous erratic material in South America is partly derived from Africa. “The Southern Brazilian tillite was, according to Coleman, derived from a sheet probably having its centre to the south-east,^[5] off the present coast-line. Both he and Woodworth also record certain erratics of a peculiar quartzite or grit with banded jasper pebbles, which from their accounts are just like those collected by the Transvaal ice from the ranges of Matsap beds in Griqualand West and transported so far westwards at least as the 18th meridian. With the continental disruption hypothesis in mind, could they not possibly have been carried much further westwards still?”

We find further agreement, as already mentioned, in the directions of the ancient folds which traverse the whole of these great gneiss plateaus. For Africa, we can refer to the map taken from Lemoine, given in Fig. 8.^[6]
Fig. 8.—Trend lines in Africa, after Lemoine. It was prepared for other purposes, and therefore does not show very clearly the facts which we need; nevertheless, it does show them. There are two more or less distinct chief directions of strike in the gneiss massive of the African continent. The older north-easterly strike predominates in the Sudan, and is to be observed in the straight, similarly directed upper course of the Niger, as far as the Cameroons. It cuts the coast at an angle of about 45°. South of the Cameroons, on the other hand, the other younger direction of strike—just recognizable on the map—predominates with a direction approximately north and south and parallel to the sinuous coast-line.

We find the same phenomena in Brazil. E. Suess writes: “The map of Eastern Guiana … shows more or less east-west strikes in the ancient rocks of which the area is composed. Also the stratified Palæozoic deposits, which constitute the northern portion of the Amazon basin, follow this trend, and the course of coast from Cayenne towards the mouth of the Amazon is therefore oblique to the strike. … So far as the structure of Brazil is known to-day, it must be assumed that up to Cape San Roque the outline of the continent also crosses the strike of the mountain chains, but from these foothills up to at least near Uruguay the position of the coast becomes defined by the mountain chains.” Here the courses of the rivers also follow in the main the strike direction (R. Amazon on one side, Rio San Franzisco and Parana on the other). It is true that more recent investigations, as shown in the tectonic map of South America given by Keidel (loc. cit.) and reproduced in Fig. 9, indicate the existence of still a third line of strike parallel to the north coast, whereby the relations become somewhat complicated. However, both the other lines of strike are very clearly shown in this map, even if they are not brought right up to the coasts. On account of the considerable rotation which South America must undergo in the reconstruction, the direction of the Amazon becomes distinctly parallel to the upper course of the Niger, so that both these strike directions will coincide with the African. We see in this yet another confirmation of a former direct connection of these continents.

It must be concluded, from palæontological and
Fig. 9.—Diagrammatic tectonic map of South America, after J. W. Evans and Keidel.

biological evidence, as will be shown later, that the exchange of forms between the land areas of South America and Africa ceased in the Lower to Middle Cretaceous. This does not contradict the assumption of Passarge,^[7] that the marginal faults of South Africa were already in existence during the Jurassic, for the rift only opened gradually from the south northwards, and, moreover, the formation of the trough faults long preceded it. In Patagonia the break had as a consequence a peculiar movement of the blocks, which A. Windhausen describes in the following manner: “The new re-orientation began with regional movements of the greatest dimensions at about the middle of the Cretaceous,” when the land surface of Patagonia “was converted from an area with a pronounced slope into a field of depression which was under the influence of arid or semi-arid conditions, and was covered with gravelly desert and sandy plains.”^[8]

The Atlas mountains lying on the northern margin of the African continent, the folding of which took place chiefly in the Oligocene, but had already commenced in the Cretaceous, find no extension on the American side.^[9] This agrees with our assumption, shown in the reconstruction, that the Atlantic rift in this region had already been open a considerable time. It is indeed probable that here also it was once quite closed, but that the opening took place before the Carboniferous. The great depth of the sea in the western portion of the North Atlantic also seems to indicate that the floor of the sea is more ancient in this region. The contrast of the Spanish peninsula with the opposite American coast has also the same bearing.^[10] The Azores, Canary Islands and Cape Verde Islands are to be conceived as fragments of the continental margin comparable to the pieces of calf-ice in front of a floating iceberg. Thus Gagel also came to the conclusion, in the case of the Canaries and Madeira, “that these islands are pieces broken off the European-African continent, from which they were first separated in comparatively recent time.”^[11]

Farther to the north we find in immediate succession three old zones of folding which extend from one side of the Atlantic to the other, and offer another very impressive confirmation for the assumption of a former immediate contact. The most striking to the eye are the Carboniferous folds, which E. Suess calls the Armorican mountains, and which make the coal deposits of North America appear as the direct continuation of the European. These strongly planed-down chains, coming from the interior of the continent, stretch in Europe at first in a curved course towards the W.N.W., then westwards so as to form a wild jagged type of coast (the so-called rias-coast) in south-western Ireland and Brittany. Traversing France, the most southerly folds of this system appear to bend round completely to the south in the continental shelf in front of that country, and to find their continuation on the Spanish peninsula on the other side of the deep-sea rift, with its book-like opening, forming the Bay of Biscay. Suess called this branch the “Asturian Eddy.” But the principal chains obviously continue westward through the more northern parts of the shelf, and though planed down by the erosion of the waves suggest a continuation into the Atlantic Ocean.^[12] As Bertrand first stated in 1887, this continuation on the American side forms the extension of the Appalachians in Nova Scotia and south-eastern Newfoundland. A folded chain of Carboniferous age also ends here, and is folded, as in Europe, towards the north. It shows, as the former does, a rias-coast, and thence traverses the shelf of the Newfoundland Bank. Its direction, usually north-easterly, changes to practically east near the place of fracture. Already according to former ideas it was assumed that it was a single great system of folds, for which E. Suess employed the term “Transatlantic Altaides.” A great simplification of this is yielded by the displacement theory, in that in the reconstruction both portions are brought into mutual contact, whilst up to the present there had to be assumed a submerged central portion that would be longer than the visible ends known to us, a fact which Penck felt a considerable time ago to be a difficulty. Several isolated elevations of the sea floor lie along the line of junction of the points of fracture which have been considered up to the present to be the tops of the submerged chain. According to our idea, they are fragments from the margin of the separating blocks, the detachment of which is easily explicable in such zones of tectonic disturbances.

Immediately to the north in Europe are folded ranges of a still older mountain system which was thrown up between the Silurian and Devonian and now traverses Norway and Scotland. E. Suess called it the Caledonian System. Andrée^[13] and Tilmann^[14] have dealt with the question of the extension of this system of mountain folding into the “Kanadische Kaledoniden” (Termier), that is, into the Canadian Appalachians, which were folded already by Caledonian movements. Naturally the agreement is not prejudiced by the fact that this Caledonian folding in America was again affected by the Armorican folding described above, which only happened here in Europe in the Hohes Venn and the Ardennes, but not in the northern part of the continent. The portions of these Caledonian folds which have been in contact are to be sought for in the Scottish Highlands and Northern Ireland on one side, and in Newfoundland on the other.

In Europe, just north of the Caledonian System, there lies the still older (Algonkian) gneissic mountain system of the Hebrides and North-west Scotland. On the American side the gneiss folds of Labrador, of similar age, which reach to the Straits of Belle Isle towards the south and extend far into Canada, correspond to these. The direction of strike is north-east–south-west in Europe; in America it varies from this to east–west. Dacqué remarks: “From this one can conclude that the chain extended across the North Atlantic Ocean.”^[15] According to former ideas, the supposed submerged connecting-link must have had a length of at least 3000 km. and the direct continuation of the European portion is, in the present position of the continents, in the direction of South America, several thousand kilometres aside from the American portion. According to the displacement theory, the American portion, in the restoration of the original conditions, undergoes such a transverse movement and simultaneous rotation, that it is directly attached to the European portion, and appears as its continuation.

Again, in the region just dealt with occur the terminal moraines of the great Pleistocene inland ice-cap of North America and Europe. In our reconstruction these also unite without leaving a gap or break, a circumstance which would surely be improbable if the coasts had at the time of their formation their present distance apart of 2500 km. especially as the American termination lies to-day 41/2° of latitude south of the European.

The correspondences of the Atlantic coasts already mentioned, namely, the folding of the Cape mountains and of the Sierras of Buenos Aires as well as the correspondence between the eruptive rocks, sediments, and strike-lines in the great gneissic plateaus of Brazil and Africa, the Armorican, Caledonian and Algonkian systems of folding, and the Pleistocene terminal moraines, in their sum-total, even if the conclusions may be still uncertain in particular questions, yield a proof, which is difficult to shake, of the validity of our supposition that the Atlantic must be considered as an expanded rift. We have also the circumstance of decisive importance that although the adjustment of the blocks must be made on the grounds of other phenomena, especially their outlines; yet by this adjustment the continuation of each structure on one side is brought into exact contact with the corresponding end on the other. It is just as if we put together the pieces of a torn newspaper by their ragged edges, and then ascertained if the lines of print ran evenly across. If they do, obviously there is no course but to conclude that the pieces were once actually attached in this way. If but a single line rendered a control possible, we should have already shown the great possibility of the correctness of our combination. But if we have n rows, then this probability is raised to the nth power. It is not a waste of time to make clear what this implies. We can assume, merely on the basis of our first “line,” the folding of the Cape Mountains and the Sierras of Buenos Aires, that the chances are ten to one that the displacement theory is correct. Since there are at least six such independent controls, 10⁶ or a million to one could be laid that our assumptions are correct. These figures may be exaggerated. But one must bear in mind, when passing judgment, what the increase in the number of independent controls really means.

North of the region hitherto considered, the Atlantic split bifurcates to both sides of Greenland and becomes narrower. The correspondences between the two sides of the Atlantic lose their value as proof, because their origin can be more and more readily explained in the present position of the blocks. Nevertheless, a complete comparison is not without interest. We find the fragments of an extensive basaltic sheet on the northern margins of Ireland and Scotland, in the Hebrides and Faroe Islands: it then changes via Iceland to the Greenland side, where in particular it forms the great peninsula bordering in the south on Scoresby Sound, and then continues farther along the coast up to latitude 75° N. Wide flows of basalt are also found on the coast of Western Greenland. At all these places coals containing land-plants occur in similar manner between two basaltic flows, whereby a former land connection has been concluded. The same result is yielded by the distribution of the terrestrial Devonian “Old Red” deposits in America from Newfoundland to New York, in England, Southern Norway and the Baltic provinces, and in Greenland and Spitsbergen. In their sum-total these discoveries give a picture of an area, united and continuous at the time of deposition, which to-day is broken up—according to former ideas, by the submergence of intermediate portions, but according to the displacement theory, by fissuring and drifting apart.

In this connection the similar occurrence of unfolded Carboniferous deposits on one side at 81° N. in north-eastern Greenland and on the opposite side in Spitsbergen is also worth mentioning.

The expected correspondence in structure also exists between Greenland and North America. According to the “Geological Map of North America” of the United States Geological Survey, numerous intrusive pre-Cambrian rocks occur in the gneiss-complex near Cape Farewell and north-west thereof. These are to be found again on the American side exactly at the corresponding places, namely, on the north side of the Straits of Belle Isle.

The displacement does not exist in the form of a dragging away from each other of the margins of the rift near Smith Sound and Robeson Channel in the north-west of Greenland, but in a lateral displacement of great dimensions, a so-called tear-fault. Grinnell Land has slid along Greenland, producing the striking straight-lined boundaries of both the blocks. This displacement can be detected in the extract given in Fig. 10, from the geological map of North-west Greenland by Lauge-Koch,^[16] if the boundary between the Devonian and Silurian, which lies in Grinnell Land at 80° 10′ N. Lat., and in Greenland at 81° 30′, is sought for.
Fig. 10.—Geological map of North-west Greenland, after Lauge-Koch.

Some reference may be made here to the manner in which the reconstruction of the pre-Atlantic continental connections was worked out. A more detailed discussion of the phenomena considered here, such as the plasticity of the blocks of sial, the melting from beneath, etc., will be given later. It is, however, necessary to mention something about them in the geological comparison of the margins of the rifts in order to prevent misconceptions.

Abrolhos Bank, on the east coast of South America, must be omitted in the fitting together of the blocks. Its jagged outline stands in sharp contrast to the practically straight course of the margin of the South American shelf, and indicates a special origin. We are probably dealing in this case with molten sialic masses (granite) from the under side of the South American block, which as a result of its displacement have emerged on its posterior edge. In a similar manner the granite masses of the Seychelles have appeared from under the margin of Madagascar or India, and, to anticipate, probably also the substructure of Iceland.

The deltaic projection of the African coast at the estuary of the Niger need not be quite omitted from the reconstruction, for the north-west of Brazil shows a corresponding but too small embayment. This projection must, however, be greatly reduced in order that the blocks may be brought into contact. It has been emphasized by several authors that not merely deltaic deposits exist there. The assumption appears to me very probable that the projection—or at least a part thereof—is a plastic deformation of the African block which we can compare with a squeezing-out. Such a process could easily have taken place in the angle between the two great lobes of North-east and South Africa. We shall learn later of another very similar process in the remarkable triangle of land in the region of the Red Sea between Abyssinia and the Somaliland peninsula. The vulcanicity along the line of fracture which traverses the Cameroons, bears the volcanic Cameroon mountain and is continued in the volcanic islands of Fernando Po, Prince’s Island, St. Thomas, and Anno Bom, may be connected with these manifestations of pressure. The phenomenon will be repeatedly met with, that volcanoes occur where the horizontal movements of the earth’s crust produce a pressure which forces the mobile inclusion of sima out of the sial blocks.

Our reconstruction of North America shows a deviation from the present map in that Labrador appears to have been pushed far to the north-west. It is assumed that the great drag, which finally led to the breaking away of Newfoundland from Ireland, caused a stretching and superficial tearing of the adjoining parts of the two blocks before the break. On the American side, not only was the Newfoundland block (including the Newfoundland Bank) broken off and rotated about 30°, but the whole of Labrador seized the opportunity to give way to the south-east, so that the previously straight rift-valley of the St. Lawrence and Belle Isle Straits acquired its present S-shaped curvature. The shallow seas of the Hudson Bay and the North Sea may have been formed or enlarged by this rupture. Thus the Newfoundland shelf undergoes by this restoration, a double change of position, namely, a rotation and a north-westward displacement, and adapts itself to the line of the shelf near Nova Scotia, over which it now juts out very far.

Iceland is assumed to lie between a double rift, a supposition to which the present depth charts of its surroundings appear to hint. Perhaps a fissure (rift-valley) was first formed between the gneiss massives of Greenland and Norway, which was then partly filled with molten sial from underneath the blocks. But since this was, for the rest, filled with sima, as the Red Sea is to-day, a renewed compression of the blocks would have the effect that this sima would be cut off from its connection with the lower regions and would be forced to the surface, thus causing the great basalt flows. That this took place in the Tertiary appears to be very plausible; the westwardly drift of South America at this time must have transmitted a moment of torsion to North America, which, as long as the anchor formed by the chains stretching from Ireland to Newfoundland remained fast, must have manifested itself in a compression north of that area.

The submarine bank of the Middle Atlantic may also be very briefly considered in this connection.^[17] The conception of Haug, who wishes to consider the whole of the Atlantic as an enormous geosynclinal and the mid-Atlantic bank as the beginning of its crumpling, is nowadays regarded by most people as insufficient. The reader need only be referred to Andreé’s criticism.^[18] According to the displacement theory, it is the former floor of the rift-valley which was in existence during the period when the Atlantic Ocean was composed of a relatively narrow fracture, which was subsequently filled with sunken margins, shore deposits, and also partly with molten sial. The islands which to-day crown the long bank were certainly formed at this time as fragments of the margins of the rift, an assumption which naturally does not prevent their visible structure being entirely volcanic. During the further continuance of the displacement these infillings still remained together in the middle between the continents. The so-called deep-sea sands, with mineral particles up to 0.2 mm. diameter, which were obviously deposited near the shore-line, but were discovered by the Valdivia Expedition and the German South Polar Expedition under Drygalski in the middle of the ocean, must be regarded as confirming our explanation, for only in this way could all portions of the sea floor have been near the shore at some earlier period.

There is, geologically, much less to be said about the other former continental connections assumed by the theory than for that severed by the Atlantic separation.

Madagascar consists, like its neighbour Africa, of a platform of folded gneiss with a north-easterly direction of strike. On both sides of the line of fracture identical marine sediments have been deposited, which show that both areas have been separated since the Trias by a flooded trough fault, a fact which is also demanded by the land fauna of Madagascar. But according to Lemoine, two animals, Potamochœrus and Hippopotamus, had immigrated from Africa in the Middle Tertiaries, when India had already moved away. These animals, Lemoine thinks, could at the most only swim an arm of the sea of 30 km. breadth,^[19] whilst the Mozambique Channel is now quite 400 km. wide. Thus the block of Madagascar must have broken loose from Africa beneath the sea after this period, which explains the great start India had, compared with Madagascar, in the displacement towards the north-west.

India is also a flat platform of folded gneiss. The folding is still visible to-day, in the very old Aravali mountains in the extreme north-west (on the edge of the Thar Desert) and in the similarly very old Korana mountains. According to Suess, the strike in the former is N. 36° E.; in the latter, to the north-east. Both strike directions thus correspond to those of Africa and Madagascar, especially with the slight rotation of India required in the reconstruction. In this context a somewhat more recent but still Mesozoic folding occurs also in the Ghats of Nellore or in the Vellakonda mountains, the strike of which is from north to south, and which agrees very well with the likewise later north-south trend-lines in Africa. The occurrence of diamonds in India is linked with that of South Africa. It is assumed in our reconstruction that the west coast of India adjoined the east coast of Madagascar. Both coasts consist of a strikingly straight fracture of a plateau of gneiss, which suggests that they could, after the formation of the rift, have slid along one another in a similar manner to Grinnell Land and Greenland. Basalt occurs on both sides at the northern end of the fracture, which on both coasts is about 10° of latitude in length. The basalt sheets of the Deccan, beginning at latitude 16° N. in India, were formed in the early Tertiary, and therefore may be brought into causal connection with the detachment. In Madagascar the most northerly portion of the island is completely built of two different ancient basalts, the date or origin of which has apparently not yet been ascertained.

The enormous folds of the Himalayan mountain system, formed essentially in the Tertiary, denote a compression of a considerable portion of the earth’s crust, by the reconstruction of which the outlines of Asia become very much altered. The whole of Eastern Asia from Tibet and Mongolia to Lake Baikal, and possibly even to the Bering Straits, probably took part in the compression. Recent work has shown that the processes of folding were by no means confined only to the Himalayas, but, for example, Eocene beds have been folded up to an altitude of 5600 m. above sea-level in Peter the Great Mountains, and great overthrusts have been produced^[20] in the Tienshan System. But even where such folding phenomena are absent, the recent elevation of undisturbed country is in just as close connection with this process of folding. The huge masses of sial, which become depressed to great depths by the folds, must be melted there and spread out beneath the adjacent parts of the blocks, which therefore become elevated. If in this connection we confine ourselves to the highest region of the Asiatic block, lying on an average about 4000 m. above the level of the sea, measuring 1000 km. in the direction of thrust, and if, in spite of the much greater elevation, we take only a similar shortening to that of the Alps (namely, to a fourth of its original length), we obtain a displacement of India of about 3000 km. India must therefore have lain near Madagascar before the thrusting began. No room remains for a submerged Lemuria, in the older sense. The traces of this gigantic thrusting together are recognizable right and left of the rather narrow thrust-zone. The breaking away of Madagascar from Africa, the whole system of recent rift-valleys in East Africa, to which the Red Sea and the Jordan valley also belong, form part of this phenomenon. The Somaliland peninsula may have been somewhat dragged round to the north, and thus be connected with the forcing up of the Abyssinian mountain system; the masses of sial, submerged beneath the melting point isotherms flowed beneath the block towards the north-east in order to spurt out in the angle between Abyssinia and the Somaliland peninsula. Arabia also felt the stress towards the north-east, and drove the outlines of the Akdar mountains, penetrating like a spur, into the Persian mountain chains. The fan-shaped grouping of the ranges of the Hindu Kush and Sulaiman mountains denotes that there the western limit of the compression is reached; its replica also occurs on the eastern margin, where the chains of hills of Burma are dragged round from a direction cutting Annam, Malacca and Sumatra to a north-south direction. The whole of the east of Asia was certainly concerned in this

Fig. 11.—The Lemurian Compression.

 

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compression, which finds its westerly limit in the echeloned folds between the Hindu Kush and Lake Baikal, and is continued up to the Bering Straits, whilst the eastern limit is formed by the bulging forms of the coast with the East Asiatic festoons of islands.

According to our assumption, the east coast of India directly adjoined the west coast of Australia. The former also displays an abrupt fracture of the plateau of gneiss, which only suffers an interruption in the narrow trough-like Godavari coalfield, composed of Lower Gondwana strata. Along the coast the Upper Gondwana beds lie unconformably on their edges. A platform of gneiss, with a rolling surface similar to that of India and Africa, is also found in West Australia. Along the coast it dips towards the sea with a long precipitous slope—the Darling range and its northern extension. In front of the steep slope is a depressed flat strip of land built of Palæozoic and Mesozoic strata which is cut through by basalt in a few places. In front of this again is a narrow strip of gneiss which occasionally disappears. On the River Irwin the strata are also coal-bearing. The strike of the folding of the gneiss in Australia is usually directed in a meridional direction, and would be converted to north-east and south-west when joined to India, and therefore parallel with the principal trend-line there.

In the east of Australia the Cordilleras, mainly folded in the Carboniferous, run from south to north along the coast, and terminate in echeloned folds which retreat successively westwards, and individually always run approximately north to south. This, as in the echelon of folds between the Hindu Kush and Lake Baikal, shows the lateral limit of the compression; the gigantic Andean folding, commencing in Alaska and traversing four continents,^[21] reaches its end here. The most westerly chains of the Australian Cordilleras are the oldest, the most eastern the most recent. Tasmania forms a continuation of this system of folding. The reflected similarity with the South American Andes in the structure of the mountain systems is interesting, for there, on account of the position on the other side of the pole, the more easterly chains are the oldest. However, the most recent chains are absent in Australia. Suess found them again in New Zealand.^[22] To be sure the folding does not extend into the Tertiary in that country: “According to the view of most New Zealand geologists, the main folding of the Maorian mountain chains occurred in the period between the Jurassic and Cretaceous.” Previously it was totally covered by sea, until the folding first “converted the region of New Zealand into a land-mass.” The Upper Cretaceous and the Tertiary are mainly marginal and undisturbed. On South Island, Cretaceous deposits only occur on the east coast, not on the west coast, where a land connection must still be assumed in the Cretaceous. The breaking-away of the west coast followed in the Tertiary, “for Tertiary marine deposits are also found on it.” Finally, in the Upper Tertiary further but smaller folds, faults and overthrusts were formed which gave the mountains their present forms.^[23] All this can be explained by the displacement theory as due to the fact that New Zealand was formerly the eastern margin of the Australian Cordilleras. But when these chains were separated as island festoons, the folding processes ceased. The Upper Tertiary disturbances can very well be brought into connection with the passing and drifting away of the Australian block.

The depth chart of the New Guinea region gives us many details of these later movements of Australia. As explained diagrammatically in Fig. 12, the great
Fig. 12.—The scattering of the chains of islands by New Guinea, diagrammatic. Australian block, with its anvil-shaped, thickened, anterior end, formed by New Guinea being folded into a high and recent mountain chain, forced itself from the south-east between the previously (probably) closed chain of the more southerly Sunda Islands and of the Bismarck Archipelago.
Fig. 13.—Depth chart of the neighbourhood of New Guinea. In the depth chart in Fig. 13,^[24] let us consider both of the southernmost rows of the Sunda Islands. The chain of the islands of Java-Wetter, striking west-east, curves spirally at its end past the Banda Islands to the Siboga Bank, successively north-east, north, north-west, west and south-west. The Timor chain of islands lying in front of it testifies by its disturbed and varying direction to the collision with the Australian shelf, for which H. A. Brouwer has given the geological reasoning in detail.^[25] This chain in addition bends back in another similar energetic spiral to Buru. A very interesting supplement to this process is to be seen on the eastern side of New Guinea. Coming from the south-east, this island has grazed the islands of the Bismarck Archipelago, grasped the island of New Britain by its former south-eastern end, and, dragging it along with itself, has turned the long island round more than 90°, bending it into a semi-circular form. A deep channel remained behind it, and testifies to the violence of this process, since the sima has not yet been able to fill it.

To many it will seem bold to draw such conclusions merely from a depth chart. But practically everywhere this is found to be a reliable guide to the movements of the blocks, especially in the later geological periods. It is also certainly worth noticing, in support of our hypothesis, that the Dutch geologists who are working in the Sunda Archipelago were the first to take up the displacement theory.^[26] As a matter of fact, numerous isolated results show the correctness of our assumptions. Thus, for example, B. Wanner explained the deep water between Buru and Sula Besi, which was unexpected tectonically, by the fact that the former has been displaced horizontally about 10 km., a supposition which fits in very well with our ideas.^[27] G. A. F. Molengraaff^[28] gives a chart of the Sunda islands in which the area with coral reefs elevated more than 5 m. is recorded. This district coincides in an astonishing manner with that in which, according to the displacement theory, the sial must be thickened by compression, that is, the whole of the area lying in front of the Australian block up to and including Celebes, apart from the south-west coasts of Sumatra and Java, as well as the north and north-west coasts of New Guinea. According to Gagel,^[29] at Cape King William in New Guinea, and also in New Britain,^[30] there are quite recent terraces which have been elevated 1000, 1250, and even probably up to nearly 1700 m. This very striking phenomenon shows that very powerful forces manifested themselves in very recent times, and agrees very well with our conception of the collision of these portions of the earth’s crust.

Two submarine ridges connect New Guinea and North-eastern Australia with the two islands composing New Zealand and appear to show the path of the displacement. They are perhaps molten masses from the underside of the block which have been left behind.

Very little can be said about the connection of Australia to Antarctica, owing to our lack of knowledge of the latter continent. A broad strip of Tertiary deposits follows the whole of the southern margin of Australia and continues through the Bass Straits, after which, however, it is first found again in New Zealand, the east coast of Australia being, however, free therefrom. Perhaps, in the Tertiary, Australia was already separated from Antarctica by a flooded rift-valley, perhaps already (apart from the Tasmanian anchor) even by deep sea. It is generally assumed that the structure of Tasmania is continued into the Antarctic Victoria Land. On the other hand, Wilckens^[31] writes: “The south-westerly curve of the mountain system of New Zealand (the so-called Otago saddle) appears to be suddenly cut short on the east coast of South Island. This termination is not natural, but depends without doubt on a fracture. The continuation of the system can only be sought for in one direction, that of the Cordillera of Graham Land, the Antarctic Andes.”

It remains still to be mentioned that the eastern end of the Cape mountains in South Africa also represent a breaking-away. According to our admittedly uncertain reconstruction of the position of Antarctica, we have to seek the continuation of these mountains between Gauszberg and Coats Land, where, however, the coasts are still quite unknown.

The connection of West Antarctica with Patagonia already mentioned is a good geological example in illustration of the displacement theory (Fig. 14). At least a limited interchange of forms still took place in the Pliocene between Tierra del Fuego and Graham Land, which was only possible if both promontories still lay in the neighbourhood of the crescent-shaped curve of the South Sandwich Islands.
Fig. 14.—Depth chart of the Drake Straits, after Groll. Since then they have drifted westwards, but their narrow connection remains stuck fast in the sima. The manner in which the echeloned successive chains were stripped off one after another from the advancing blocks and were left behind is distinctly seen in the depth chart.^[32] The group of the South Sandwich Islands, lying directly in the middle at the place of rupture, has become most strongly curved by this process of movement; the inclusions of sima were squeezed out by it. The islands are basaltic, and one of them (Zawadowski Island) still shows volcanic activity. Moreover, according to F. Kühn,^[33] the late Tertiary Andean folding is absent on the whole chain of the South Antillean curve, whilst the more ancient folds are known in South Georgia, South Orkneys, etc. These peculiarities are readily explained by the displacement theory, for if the folding in South America and Graham Land was actually produced by the westerly drift of the blocks, it must have ceased in the South Antillean curve at the time when the latter remained stationary.

In this connection the Permo-Carboniferous glacial phenomena which are found everywhere on the southern continents could be adduced to prove the displacement theory, for they form—in a similar manner to the Old Red in the Northern hemisphere—the fragments of a single land-mass which can be explained much more easily by the displacement theory than by that of the submerged bridging-continents, because of their great distance apart. However, this phenomenon will be described in more detail in the sixth chapter, because it is first and foremost a question of climate.

1. H. Keidel, Über das Alter, die Verbreitung und die gegenseitigen Beziehungen der verschiedenen tektonischen Strukturen in der argentinischen Gebirgen. Étude faite à la XII^e Session du Congrès géologique international, reproduite du Compte-Rendu, pp. 671–687 (separate, n.d.). See also a detailed account by the same author: J. Keidel, La Geología de las Sierras de la Provincia de Buenos Aires y sus Relaciones con las Montañas de Sud Africa y los Andes. Annales del Ministerio de Agricultura de la Nación, Sección Geología, Mineralogía y Minería, Tomo XI, Núm. 3, Buenos Aires, 1916.
2. This, of course, does not happen if these distances are measured from the 1000 m. depth-contour at Cape San Roque and the Cameroons respectively, as the opponents of the theory have done. The continents do not agree at all well with these depth-contours. It will be shown later that the old contours are much better preserved in the upper part of the continental margin, whilst the lower portions flow sideways. The junction, therefore, must as a rule be made at the upper margin of the steep slope to the deep sea.
3. H. A. Brouwer, “De alkaligesteenten van de Serra do Gericino ten Noordwesten van Rio de Janeiro en de overeenkomst der eruptiefgesteenten van Brazilië en Zuid-Afrika,” Kon. Akad. van Wetensch. te Amsterdam, Deel 29, pp. 1005–1020, 1921.
4. Alex. L. du Toit, “The Carboniferous Glaciation of South Africa,” Trans. Geol. Soc. S. Africa, 24, pp. 188–227, 1921.
5. This is written, by an oversight, as “south-west” in the original.
6. P. Lemoine, “Afrique occidentale,” Handb. d. Regionalen Geologie, vol. vii, 6a, Part 14, p. 57. Heidelberg, 1913.
7. S. Passarge, Die Kalahari, p. 597. Berlin, 1904.
8. A. Windhausen, “Ein Blick auf Schichtenfolge und Gebirgsbau im südlichen Patagonien,” Geol. Rundsch., 12, pp. 109–137, 1921.
9. Gentil, however, is able to see such a continuation in the contemporary mountains of Central America, especially the Antilles. Jaworski, on the other hand, has rejected this on the ground that it is incompatible with the generally accepted idea of E. Suess, according to which the eastern cordilleran curve of South America crosses over into the Lesser Antilles, and thence bends back again to the west without sending off projections to the east.
10. This is held by many to be an objection to the displacement theory. The Devonian strata in particular on the North American coast require a greater land mass to the east than could be given by Spain, with its anomalous structure. On the other hand there is the continental shelf to be taken into account, which extends far in front of the American coast. But it is impossible to take up any strong view on this question so long as the size and the outline of the Spanish block in the Devonian period are not known. At present this is impossible, because the Carboniferous as well as the Tertiary folds which traverse the Iberian peninsula in thick swarms would have to be smoothed out. But as long as the displacement theory declares itself for these reasons unable to carry out the reconstruction of this region for the Devonian period, no one can tell whether the American Devonian will afford refutation or confirmation.
11. C. Gagel, “Die mittelatlantischen Vulkaninseln,” Handb. d. regional. Geologie, vol. vii, Part 4. Heidelberg, 1910.
12. The view of Koszmat (“Die Mediterranen Kettengebirge in ihrer Beziehung zum Gleichgewichtszustande der Erdrinde,” Abh. d. Math.-Phys. Kl. d. Sächsischen Akad. d. Wiss., 38, No. 2, Leipzig, 1921) differs from that of Suess in that the European folds collectively turn round in the oceanic area and return towards the Iberian peninsula. This is very difficult to uphold, since such a great curve of folds cannot be provided for in the continental shelf.
13. K. Andrée, “Verschiedene Beiträge sur Geologie Kanadas,” Schriften d. Ges. z. Beförd. d. ges. Naturwiss. zu Marburg, 13, 7, p. 437. Marburg, 1914.
14. N. Tilmann, “Die Struktur und tektonische Stellung der kanadischen Appalachen. Sitzber. d. Naturwiss., Abt. d. Niederrhein. Ges. f. Natur-. u. Heilkunde in Bonn, 1916.
15. E. Dacqué, Grundlagen und Methoden der Palägeographie, p. 161. Jena, 1915.
16. Lauge-Koch, “Stratigraphy of North-west Greenland,” Meddelelser fra Dansk geologisk Forening, 5, No. 17, pp. 1–78, 1920.
17. Compare the chart of the Atlantic Ocean given in Schott, Geographie des Atlantischen Ozeans. Hamburg, 1912.
18. K. Andrée, Über die Bedingungen der Gebirgsbildung, p. 86, etc. Berlin, 1914.
19. P. Lemoine, “Madagaskar,” Handb. d. regional. Geol., vol. vii, 4, Part 6, p. 27. Heidelberg, 1911.
20. R. von Klebelsberg, “Die Pamir-Expedition des Deutsch. u. Österr. Alpen-Vereins vom geologischen Standpunkt,” Zeitschr. d. Deutsch. u. Osterr., A.–V., 1914 (45), pp. 52–60, as well as communications by letter to the author. His chief work has not yet been published.
21. North and South America, Antarctica and Australia.
22. E. Suess, Das Antlitz der Erde, Vol. 2, p. 203. Vienna, 1888. Sollas, English edition, Vol. 2, p. 162. Oxford, 1906.
23. O. Wilckens, “Die Geologie von Neuseeland,” Die Naturwissenschaften, 1920, Heft 41. Also in Geol. Rundsch., 8, pp. 143–161, 1917.
24. The excellent map of the Sunda Islands in G. A. F. Molengraaff, “Modern Deep-sea Research in the East Indian Archipelago,” Geogr. Journ., 1921, pp. 95–121, giving land elevations and sea depths at similar intervals, is the clearest for this purpose.
25. H. A. Brouwer, “On the Crustal Movements in the Region of the Curving Rows of Islands in the Eastern Part of the East Indian Archipelago,” Kon. Ak. v. Wetensk. te Amsterdam Proceed., 22, Nos. 7 and 8, 1916. (Also Geol. Rundsch., 8, Heft 5–8, 1917, and Nachr. d. Ges. d. Wissensch. z. Göttingen, 1920.)
26. G. A. F. Molengraaff, “The Coral Reef Problem and Isostasy,” Kon. Akad. van Wetensch., 1916, p. 621 (note). L. van Vuuren, Het Gouvernement Celebes, Proeve eener Monographic, 1, 1920 (especially pp. 6–50). Wing Easton, “Het onstaan van der maleischen Archipel. bezien in het licht van Wegener’s hypothesen,” Tijdschrift van het Kon. Nederlandsch Aardrijkskundig Genootschap., 38, No. 4, pp. 484–512, 1921; also, “On Some Extensions of Wegener’s Hypothesis and their Bearing upon the Meaning of the terms Geosynclines and Isostasy,” Verh. van het Geolog.—Mijnbouwkundig Genootschap voor Nederland en Kolonien, Geolog. Ser., Deel V, pp. 113–133, 1921. (I cannot in any way agree with the proposed modifications of the displacement theory by this author.)
27. B. Wanner, “Zur Tektonik der Molukken,” Geol. Rundsch., 12, p. 160, 1921.
28. G. A. F. Molengraaff, De Geologie der Zeeën van Nederlandsch Oost-Indië (Overgedrukt uit: De Zeeën van Nederlandsch Oost-Indië. Leyden, 1921).
29. C. Gagel, “Beiträge zur Geologie von Kaiser-Wilhelmsland,” Beitr. z. geol. Erforsch. d. Deutsch. Schutzgebiete, Heft 4, pp. 1–55. Berlin, 1912.
30. K. Sapper, “Zur Kenntniss Neu-Pommerns und des Kaiser-Wilhelmslandes,” Petermann’s Mitt., 56, pp. 89–123, 1910.
31. O. Wilckens, “Die Geologie von Neuseeland,” Geol. Rundsch., 82 pp. 143–161, 1917.
32. The best chart of the Drake Straits is that drawn by H. Heyde, which is reproduced by F. Kühn (see page 72). The deviations of our figure from it are unimportant.
33. F. Kühn, “Der sogenannte ‘Sudantillen-Bogen’ und seine Beziehungen,” Zeitschr. d. Ges. f. Erdk. z. Berlin, pp. 249–262, 1920.