This report presents the results of a detailed correlation analysis which reveals a remarkable correspondence between variations in seafloor spreading rates and marine taxonomic diversity.

Scott and Balleny Islands are volcanic edifices in the Ross Sea. Scott Island rocks are phonolites similar to rocks found in the Hallett volcanic province, Antarctica. New samples from the Balleny Islands presented in this paper are undersaturated alkali lavas identical to those on other oceanic islands. It is suggested that intraplate stress within the Antarctic plate may be responsible for the Scott and Balleny Islands and other large seamount groups within the Ross Sea.

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New aeromagnetic data, K‐Ar age determinations of dredged marine igneous rocks, as well as other geophysical evidence have shed light on the chronology, nature and evolution of the northern Iceland Plateau. Correspondence between seismic refraction profiles taken on the Jan Mayen Ridge and westward through Jan Mayen Island, suppressed aeromagnetic anomalies, earthquake surface wave studies, and ages of dredged igneous rocks suggest these strata may form an extended region of thickened crust, possibly of Caledonian age, extending westward toward the Kolbeinsey Ridge and northwest to the south wall of the Jan Mayen Fracture Zone.

It has long been recognized that the fossil record is characterized by a number of major extinction episodes, but the cause of these remains a controversy. Among the many suggested factors, a correlation with major rifting events has often been postulated [e.g., Hallam, 1984; Valentine and Moores, 1970], and we feel that the implication of this deserves much greater attention. The widespread volcanism, both submarine and subaerial, associated with such mega‐tectonic events with energy much greater than 1030 ergs, offers a natural explanation for several of the features that have been linked with extinction crises. The occurrence of widespread submarine volcanism is likely to have been especially important in promoting massive marine extinctions through chemical and biologic mechanisms. Of the numerous extinction events cited in the literature, there are five major episodes for which there is widespread agreement, and several minor ones (Figure 1). Significantly, each of these can be correlated with an important volcanic event, and the correlation is especially strong for the three more recent major crises for which data is available (Table 1). These are the ones occurring at the ends of the Permian, Triassic, and Cretaceous periods.