On the other hand, the age of the birth of the Pacific plate was determined assuming that all triple junctions had kept their configurations for about 30 m.y. Previous studies indicate instability of the configuration of the triple junctions from Late Jurassic to Early Cretaceous (155-125 Ma). The major tectonic events as the formation of oceanic plateaus and microplates during the period occurred in the vicinity of the triple junctions, implying that the study of the triple junctions is indispensable for understanding the tectonic evolution of the Pacific plate. The plate boundary surrounding the Pacific plate from Early Jurassic to Early Cretaceous involved the four triple junctions among Pacific, Izanagi, Farallon, and Phoenix plates. The size of the Pacific plate at 190 Ma was nearly half that of the present Easter or Juan Fernandez microplates in the East Pacific Rise. It was born as a microplate aroud the Izanagi-Farallon-Phoenix triple junction about 192 Ma, Early Jurassic. The Pacific plate is the largest oceanic plate on Earth. We present the tectonic evolution of the Jurassic Pacific plate based on magnetic anomly lineations and abyssal hills. Tectonic Evolution of the Jurassic Pacific Plate
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