Increasing evidence for globally synchronized magmatic episodes, affecting both hot spots and subduction zones, may be of major significance for understanding climatic and other phenomena not accounted for by present plate tectonic models. The dramatic Pliocene-Pleistocene increase in volcanic activity–and coeval climatic deterioration–casts doubt on the uniformitarian view of the Mid-Atlantic rift valley as a wholly steady-state feature. It seems not unlikely that the mid-oceanic ridge–the most impressive volcanic feature on this planet–has also recorded these episodes in some manner, even far from hot-spot influence.

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