Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay
On these diagrams, pairs of parallel lines show boundaries where plates are spreading apart, lines with ticks show boundaries where plates are colliding, and simple lines show other types of boundary. These include places where plates are simply sliding past one another, places where motions are too complex to portray simply, and places where new plate boundaries may be forming.
The Pacific Plate is unusual in that it is almost entirely oceanic crust. Only in a few places like Baja California and southern New Zealand are small slivers of continental crust attached. The continents are moving away from the Atlantic and Indian Oceans and converging on the Pacific. Most of the Pacific is surrounded by subduction zones.
The mid-ocean ridge in the Pacific, the East Pacific Rise, is bounded on the east by the Cocos and Nazca Plates. When North America was further east, the East Pacific Rise extended all the way to Alaska and the Nazca, Cocos and Juan de Fuca Plates were a single large plate, which geologists call the Farallon Plate. About 30 million years ago North America came into direct contact with the Pacific Plate and the Juan de Fuca Plate was cut off from the rest of the Farallon Plate. Today only a small remnant of it remains.
In addition to the large plates, significant small plates are labeled. Very small plates are not labeled.
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Created 25 July 2009, Last Update 15 January 2020