The North American Plate is one of the slowest, averaging around 1 cm/y in the south up to almost 4 cm/y in the north. The Pacific Plate is the fastest at over 10 cm/y in some areas, followed by the Australian and Nazca Plates. Rates of motions of the major plates range from less than 1 cm/y to over 10 cm/y. Figure 10.16 A map showing 15 of the Earth’s tectonic plates and the approximate rates and directions of plate motions.
For example the Juan de Fuca Plate is actually three separate plates (Gorda, Juan de Fuca, and Explorer) that all move in the same general direction but at slightly different rates. There are also numerous small plates (e.g., Juan de Fuca, Nazca, Scotia, Philippine, Caribbean), and many very small plates or sub-plates. The major plates are Eurasia, Pacific, India, Australia, North America, South America, Africa, and Antarctic. By the end of 1967, Earth’s surface had been mapped into a series of plates (Figure 10.16).
10.4 Plates, Plate Motions, and Plate-Boundary ProcessesĬontinental drift and sea-floor spreading became widely accepted around 1965 as more and more geologists started thinking in these terms.
