Hypothesis Of Drift Research Articles

Uniformitarianism--Or Uniformity: GEOLOGICAL NOTES

Although radiometric dating may at some in the future provide data from which to construct a calendar of geologic time, the chronologic foundation of the present geologic scale has been, and is, fossils. In reality the of stratigraphic classification is the time unit (series and stage) and not the time-stratigraphic unit. From the time-stratigraphic unit we have derived the concept of the time unit. The idea of the type section has been strongly emphasized in the United States from an early date. The type section for a rock-stratigraphic is at best only typical of what the original describer saw and should not be used to freeze the concept intended. Paradoxically, although we give lip-service to an awareness of isochronous but different facies when we write, in practice we say that similarity implies isochroneity - in other words, the doctrine of uniformitarianism becomes the doctrine of uniformity. A long distance today between homotaxial sequences can support the hypothesis of isochroneity or the hypothesis of continental drift without proving either one.

Necessity for Continental Drift

A forthcoming series of publications is designed to re-introduce the hypothesis of continental drift in a modified form. Firstly, therefore, is examined the necessity for thinking in terms of the hypothesis; and the chief reason is found in the lucid explanations it offers of well established geologic correspondences between various continents. Other hypotheses fail signally in this respect. A new and spectacular test of stratigraphic comparison between South Africa and Antarctica is suggested.

THE GEODETIC EVIDENCE CONCERNING WEGENER'S HYPOTHESIS

Twenty years ago there seemed to be many good reasons for supposing that Wegener's hypothesis of Continental Drift was untenable. There seemed to be unsurmountable objections to it from a point of view of a mechanism capable of causing tectonic movements of such magnitude; there was disagreement over the correspondence of the orogenic belts in the areas of the earth which are supposed formerly to have been united, as well as over other major geological factors; there was the gravest discordance between the known palaeontological facts and those demanded by the theory; after examination of the geodetic evidence, at least one distinguished geodesist pronounced that it was insufficient. General opinion to-day has perhaps changed and there now appears to be a marked tendency to recognise the cogency of some of Wegener's general arguments and to pay greater attention to the possibilities which he propounded, because it is becoming increasingly clear that the question of the arrangement and of the stability of the primary structural units of the Earth's surface, during geological time, is one of the fundamental problems of geology, as well as of all the allied subjects of geophysics, geomorphology, geodesy, palaeoclimatology and palaeontology. This is the writer's opinion, for what it is worth, after studying the considerable literature on this important and fascinating subject which has accumulated in the course of the past 30 years, during part of a recent leave spent in “browsing” round the Schools and libraries of Cambridge University.

THE GEODETIC EVIDENCE CONCERNING WEGENER'S HYPOTHESIS

Twenty years ago there seemed to be many good reasons for supposing that Wegener's hypothesis of Continental Drift was untenable. There seemed to be unsurmountable objections to it from a point of view of a mechanism capable of causing tectonic movements of such magnitude; there was disagreement over the correspondence of the orogenic belts in the areas of the earth which are supposed formerly to have been united, as well as over other major geological factors; there was the gravest discordance between the known palaeontological facts and those demanded by the theory; after examination of the geodetic evidence, at least one distinguished geodesist pronounced that it was insufficient. General opinion to-day has perhaps changed and there now appears to be a marked tendency to recognise the cogency of some of Wegener's general arguments and to pay greater attention to the possibilities which he propounded, because it is becoming increasingly clear that the question of the arrangement and of the stability of the primary structural units of the Earth's surface, during geological time, is one of the fundamental problems of geology, as well as of all the allied subjects of geophysics, geomorphology, geodesy, palaeoclimatology and palaeontology. This is the writer's opinion, for what it is worth, after studying the considerable literature on this important and fascinating subject which has accumulated in the course of the past 30 years, during part of a recent leave spent in “browsing” round the Schools and libraries of Cambridge University.

Illustrated Flora of the Pacific States

THE region of the Pacific States with which the book under review deals is of great interest to the student of geographical distribution and the taxonomist. The area is peculiarly rich in endemic genera and species, and this is especially true of California. The Pacific States show interesting geographical connexions with the flora of Eastern Asia in genera, however, which are probably too recent in origin to be adduced in support of any hypothesis of continental drift, but are to be regarded rather as evidence of the similarity of ecological conditions and the high efficiency of dispersal agents, not perhaps excluding man himself. Thus the saxifragaceous species Leptarrhena pyrolifolia is native both to the coastal regions of north-west America and to eastern Asia. Again, the genus Pectiantia comprises five species of which three are endemic to the Pacific States, whereas the other two are natives of Japan. But it is in the endemics of the region that the chief interest of the flora rests. Some of these, such as Romneya Coulteri, the genera Eschscholtzia and Lewisia, are familiar to British horticulturists. In the family Polygonaceae the monotypic genera Gilmania, Nemacaulis and Hollisteria are all endemic to California while of the 150 known species of Eriogonum 80 are found in the Pacific States, many of them endemic. In the Crassulaceae there are some 35 endemic species belonging to the genera Sedella, Budleya, Stylophyllum, Hasseanthus and Gormania. In the Cruciferse most of the species of Thelypodium, Streptanthus and Caulanthus are endemic. The Rosacese, too, provide a large number of endemics, particularly in the genera Horskelia (19 spp.) and Ivesia (17 spp.). In the Leguminosse the outstanding genera in this respect are Lupinus, of which 58 species are probably endemic, Hosackia, of which most of the 39 species are endemic, while Astragalus is represented by 137 species of which 83 are probably endemic. Illustrated Flora of the Pacific States Washington, Oregon and California. By Leroy Abrams. In 4 vols. Vol. 2: Polygonaceae to Krameriaceae, Buckwheats to Kramerias. Pp. viii + 635. (Stanford University, Calif.: Stanford University Press; London: Oxford University Press, 1944.) 45s. 6d. net.

Regionale Geologie der Erde

DR. G. DE P. COTTER, until recently a superintendent of the Geological Survey of India, has utilized the experience of a lifetime spent in the field in India in summarizing the present state of knowledge of the geology of the peninsula. There are no Palaeozoic rocks there older than the Talchir Boulder Bed at the base of the Gond-wanas, which is regarded, with fair confidence, as Upper Carboniferous. The glaciation was more intense in the south, where ice-scratched rockfloors and boulders occur, whereas in the Himalayas (in Spiti and Kashmir) the representative of the Boulder Bed is a basal conglomerate which may have been deposited by floating bergs. Since India is the only land north of the equator where the Boulder Bed occurs, Cotter is inclined to accept the hypothesis of continental drift and to regard the Indian fragment of Gondwanaland as having drifted northwards from its original home south of the equator, leaving behind it portions of its mass in Madagascar, the Chagos archipelago and the submerged land which forms the platform of the Maldives and Laccadives. Elsewhere the latter is regarded as the extension of the Aravalli Range. Regionale Geologie der Erde Herausgegeben von Karl Andree H. A. Brouwer W. H. Bucher. Band 1, Abschnitt 6: The Indian Peninsula and Ceylon, by G. de P. Cotter. Pp. 66 + vi. (Leipzig: Akademische Verlags-gesellschaft m.b.H., 1938.)

Antarctica and Glacial Ages

PROF. A. P. COLEMAN1 contends that the late Palaeozoic glacials of the southern hemisphere could never have been formed upon a large, single continent—Gondwana—as visualized by supporters of the hypothesis of continental drift. He has protested that, for such an ice-cap to have developed, there must have been sources of evaporation at hand in the shape of warm seas, and has accordingly denied the existence of any such continent and along with it the hypothesis of drift. It is difficult to follow his argument in the face of recent work on this problem.

Vorlesungen über Physik der Atmosphäre

IN 1911 there appeared an attractive and highly individual book by Alfred Wegener, entitled “Thermodynamik der Atmosphare”. Under this somewhat forbidding title a wide range of atmospheric topics was discussed, with originality and insight if not always with adequate critical judgment. The book met with a favourable response, and was reprinted without alteration in 1924 and 1928, circumstances preventing the author from making the changes and. extensions called for by the advance of knowledge. Meanwhile Wegener achieved world-wide fame as the author of the hypothesis of continental drift, which he expounded in a well-known and much discussed book; he also led a number of scientific expeditions, and unfortunately, in the last of these, to Greenland, he met his death. Vorlesungen uber Physik der Atmosphare Von Prof. Alfred Wegener Prof. Kurt Wegener. Pp. xii + 482. (Leipzig: Johann Ambrosius Earth, 1935.) 36 gold marks.

The Hypothesis of Continental Drift

THE late Dr. A. Wegener claimed the advantage for his hypothesis of continental drift that it could be tested by making repeated astronomical observations of the positions of land stations; for drifts at the rates of only a few feet a year would suffice to carry the land masses far within the span of geological time. Few geologists would in respect to this problem deny the applicability of the dictum that the present is the key to the past; the question is whether precision determinations of position will give measurable results within a reasonable time.

Wegener's Hypothesis of Continental Drift

Wegener's Hypothesis of Continental Drift

Wegener's Hypothesis of Continental Drift

WEGENER'S hypothesis is based on the idea VV that the continental masses are patches of lighter rock floating and moving in a layer of denser rock, and this denser rock forms the floor of the oceans. Following, with a slight alteration, the terminology of Suess he calls the lighter material the Sial and the denser layer the Sima. Suess uses the words Sal and Sima, and thinks that the Sal covers the globe completely.