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Abstract The general theme of this publication is the assessment and reassessment of various data, observations, and ideas about the earth as they relate to the concept that has come to be known as plate tectonics. Much widely scattered material was brought together for this publication, and its 24 papers contain an abundance of worldwide references that are important in studying plate tectonics.

Abstract Data from field geology, structural geology, stratigraphy, paleontology, geophysics, and oceanography are brought to bear on the problems of plate tectonics. Many data favor the concept, whereas many do not. A definitive work on the correctness, or incorrectness, of the plate-tectonics concept has yet to be written because present data are insufficient to make a final assessment.

Abstract The present ruling theory of geotectonics—commonly known as the "new global tectonics"—includes the concepts of plate tectonics, seafloor spreading, continental drift, and polar wandering. Recent seismic activity defines the positions and relative movements of rigid lithosphere plates. The geomagnetic time scale for polarity reversals seems to be calibrated to about 4 m.y. ago, and extrapolated to about 80 m.y. ago by correlation of oceanic magnetic anomalies with reversals and seafloor spreading. Seafloor spreading and the magnetic anomalies thus indicate the directions and rates of movements of lithosphere plates during the last 80 m.y. The continents drift with the lithosphere plates, and independent paleomagnetic evidence permits location of the relative positions of the continents and the poles to 500 m.y. ago, or more. The theory, which explains phenomena previously unexplainable, is supported by a mass of persuasive evidence. There is no doubt that the theory is a success, but it has been so successful that it has become a ruling theory, and subservience to a ruling theory never has served science well. There are data which do not seem to fit the theory. We should strive to keep open minds and to search for alternate solutions to fit all of the data. The record is clear: today's history was yesterday's model. Dare we conclude that at last we know the answers?

Abstract Many aspects of the so-called “new global tectonics” or plate-tectonics theory were proposed by geologists three or more decades ago. Included among these concepts are continental drift, the worldwide continuity of the midocean ridge and rise system, seafloor spreading, underthrusting of oceanic crust along trenches and the concept of subduction, collision of continental plates to form Alpine-type mountains, and the concept of plate tectonics itself. Geologists who perceptively formulated theories of worldwide interrelations between extensional zones and compressional belts include Daly, Du Toit, Griggs, and Holmes. What was lacking for an initial broad acceptance or refutation of any concept of global tectonics was adequate supporting data, primarily of a geophysical nature and particularly from the vast oceanic regions. The recent geophysical contributions in the formulation of plate-tectonics theory are significant, but the essential role of geology and the imaginative contributions of earlier geologists in the formulation of many concepts basic to plate tectonics should not be minimized or forgotten.

Abstract The validity of a comprehensive hypothesis such as the "new global tectonics" may be tested on the basis of either pragmatic usefulness or scientific acceptability. Unquestionably, this hypothesis has been extremely successful pragmatically in relating diverse geological and geographical observations and conjectures, thus sparking a revolution in the earth sciences, the effects of which will determine the dominant directions of research for years to come. Tests of the scientific validity of such a wide-ranging hypothesis are difficult to design and apply. The most convincing tests will involve prediction of behavior unrelated to the phenomena which the hypothesis was devised to explain. It is not surprising that the hypothesis is especially successful for the oceans. However, its application to orogenic belts, to deformation within continents, and to paleogeologic and paleoclimatic reconstructions is less obvious and has yet to be evaluated. These are difficult exercises. The demonstration that diverse geologic facts and inferences can be rationalized is permissive, but not compelling, evidence of scientific validity; essentially the same data have served to validate other quite different hypotheses. This paper points out some of the apparent weaknesses of the new-global-tectonics hypothesis and suggests some possible tests of the major tenets of the hypothesis.

Abstract Geological and geophysical data from the ocean basins and the continents are now sufficiently abundant to demonstrate that all proposed models for the new global tectonics contain serious errors. For example, several sets of paleoclimatic data—specifically, the distribution on the continents and shelves of ancient evaporites, carbonate rocks, coals, and tillites—appear to be explicable only if the present positions of the rotational axis, continents, and ocean basins have been constant for at least 1,600 m.y. The distributions of fossil invertebrate and tetrapod faunas and floras likewise indicate the constancy of position of the rotational axis, continents, and ocean basins for at least 570 m.y. Faunal-realm studies are proving to be extremely useful, because many of them demonstrate that the continents have been in about their present relative positions since Proterozoic time. A possibly fatal flaw in the plate-tectonics hypothesis is that the topologic requirements for moving the Americas away from Eurafrica eliminate any possibility of such movement unless the earth has expanded greatly during the last 150–200 m.y. Studies of climatic and biozoologic zones of the Mesozoic and Cenozoic show that expansion has not taken place. Other space requirements for the continents do not permit east-west movements since Archean time in the Northern Hemisphere, a conclusion now confirmed by the presence of continental crust across the North Atlantic beneath the Faeroe-lceland-Greenland ridge. North-south movements of individual continents are limited to a few hundred kilometers—on the basis of paleoclimatic and paleontologie data. Movements involving the “opening” and “closing” of the Tethys—from present-day Spain to New Guinea—are restricted to distances of less than 300 km by detailed field geological and geophysical studies. If seafloor spreading is taking place in the Tethyan belt, lateral movements have been—and are—restricted to mantle movements and the overlying lithosphere is detached from the mantle. Ocean-basin studies show that island-arc trench fills, where subduction supposedly takes place, are undeformed. The volumes of undeformed sedimentary rocks in Layer 1 indicate that either (1) seafloor spreading has not taken place since late Mesozoic or earlier time, (2) subduction must take place seaward from the island arc trenches, or (3) there is no such process as subduction. Detailed studies of the Lesser Antilles and Tonga-New Zealand arcs prove that aseismic island chains seaward from both arcs have been in their same relative positions since mid-Mesozoic and late Paleozoic times, respectively. Preliminary studies of several other island-arc systems lead to similar conclusions. Sediment fills in fracture zones crossing midocean ridges also are undeformed—a remarkable fact if seafloor spreading is taking place. Many of these fractures continue onshore into the continents, where the proved senses of movement are the opposite of those predicted by "transform-fault" solutions. “Transform-fault” solutions, moreover, are accounted for more logically by known gravity models of midocean ridges than by hypothetical “plate” motions. JOIDES drilling results have been hailed as a “remarkable confirmation” of plate-tectonics predictions. Numerous alleged basalt basements have baked upper contacts, so that it is doubtful that such basalts really are basement. The first dating of such basalts from JOIDES coreholes beneath Mesozoic rocks showed the basalt to be late Tertiary or younger. Thus another prop of the new global tectonics begins to crumble, and the age of the ocean basins remains unknown. A possible clue to the age of the ocean basins is the increasing number of discoveries of ancient rocks from the ocean basins and midocean ridges. Rocks ranging in age from 797 m.y. to 1,590 m.y. have been found from the Atlantic, the Pacific, and possibly the Indian Oceans. None of the ancient samples fit modern notions of plate tectonics.