Plate Tectonics, Seafloor Spreading, and Continental Drift: an Introduction1
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?
Figures & Tables
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.