Interpretation of the detailed patterns of ocean‐floor transforms revealed by satellite altimetry enables the creation of the Indian Ocean to be described quantitatively as four consecutive plate‐tectonic regimes separated at 200, 136, 89 and 43 Ma. Each regime is reversed in turn by keeping transform termini coincident and colinear until conjugate points on the margins of pre‐existing plates regain their pre‐regime integrity. Progressive elimination of the Indian Ocean, demonstrable as a smooth computer animation (http://www.kartoweb.itc.nl/gondwana), leads to a refined re‐assembly of the continental fragments of central Gondwana that is substantiated by new geological data. A sequence of Euler interval poles that describes the dispersal of the Gondwana fragments, time‐calibrated against available magnetic anomaly data, is given. The model requires a mid‐Cretaceous position for India’s southern tip about 1000 km south of Madagascar, prior to India’s rapid northward migration.

We present a new plate tectonic model for the breakup and dispersal of East and West Gondwana and subsequent formation of the Indian Ocean, focussed on the early evolution of the Eastern Margin of Africa. We start from a tight reconstruction of all the Precambrian pieces. Using primarily ocean-floor fracture zone data, the development of the ocean between India and Antarctica is resolved into four distinct spreading regimes and that between Antarctica and Africa into seven distinct regimes. The movement of Madagascar against Africa is then investigated as part of the plate–circuit closure between Africa and India in the Madagascar–Africa–Antarctica–India–Madagascar system. We conclude that a distinct change in plate tectonic regime off East Africa occurred at about 153 Ma (Kimmeridgian) when transforms were first activated offshore. Before this time, East and West Gondwana were separated by a rift, propagating from NE to SW and starting between 188 and 170 Ma. The model is defined by Euler interval poles, published here for the first time, and a refined global animation that may be inspected and copied from the URL www.reeves.nl/Gondwana. The analysis points to a small number of disruptive events in the otherwise inexorable growth of the oceans.

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There is a continuous large demand for gravity and magnetic surveys all over the world for a variety of exploration applications, all of which require the geophysicist to provide some new insight into the geology of an area at scales ranging from very large to very small. To achieve this objective, (a) surveys must be carried out accurately, and (b) their results must be interpreted in sympathy with what is already known of the geology. The methodology for acquiring and compiling data appears to be keeping pace with modern technology. Methods of quantitatively interpreting anomalies in terms of models of causative bodies are adapting rapidly to the burgeoning availability of computing power, from large, powerful machines to inexpensive and field‐portable microcomputers. Geologic interpretation, or the identification of physical property distributions in terms of realistic geologic models and processes, is still relatively neglected—in practice and, regretably, in the geophysical literature. Research into the relationships between physical rock properties—particularly magnetite distribution—and geology is gaining momentum, but research still lags behind the requirements of the conscientious geophysical interpreter.

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