<P> In the south - west, the Pacific Plate has a complex but generally convergent boundary with the Indo - Australian Plate, subducting under it north of New Zealand forming the Tonga Trench and the Kermadec Trench . The Alpine Fault marks a transform boundary between the two plates, and further south the Indo - Australian Plate subducts under the Pacific Plate forming the Puysegur Trench . The southern part of Zealandia, which is to the east of this boundary, is the plate's largest block of continental crust . </P> <P> The northern side is a convergent boundary subducting under the North American Plate forming the Aleutian Trench and the corresponding Aleutian Islands . </P> <P> The Pacific Plate is almost entirely oceanic crust, but it contains some continental crust in New Zealand, Baja California, and coastal California . </P> <P> The Pacific Plate has the distinction of showing one of the largest areal sections of the oldest members of seabed geology being entrenched into eastern Asian oceanic trenches . A geologic map of the Pacific Ocean seabed shows not only the geologic sequences, and associated Ring of Fire zones on the ocean's perimeters, but the various ages of the seafloor in a stairstep fashion, youngest to oldest, the oldest being consumed into the Asian oceanic trenches . The oldest member disappearing by way of the Plate Tectonics cycle is early - Cretaceous (145 to 137 million years ago). </P>

How much of the pacific plate is oceanic crust vs continental crust