East Pacific Rise
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The East Pacific Rise is a long north-south welt of seafloor spreading under the eastern Pacific Ocean from near Antarctica in the south northward to its termination at the northern end of the Gulf of California in the Salton Sea basin in southern California. The rise is a constructive tectonic plate margin or divergent boundary lying along the eastern margin of the Pacific Ocean basin. The spreading zone separates the Pacific Plate to the west from (south to north) the Antarctic Plate, the Nazca Plate, Cocos Plate, and the North American Plate.
[edit] Overview
The volcanic Galapagos Islands are located above a hotspot on the Galapagos Rise, a spreading zone that extends east from a triple junction with the Pacific Rise. This triple junction separates the Pacific, Nazca, and Cocos plates, but in a unique manner: a small microplate, the Galapagos Microplate, occupies the triple point, rotating clockwise between the surrounding larger plates.
The rise lies in part under the Gulf of California and southern-most part of the Salton Sea where it terminates at its junction with the San Andreas Fault. The San Andreas is a transform fault boundary between the East Pacific Rise and the Gorda Ridge off the coast of Oregon.
The oceanic crust is moving away from the East Pacific Rise to either side. On the eastern side the eastward moving plates meet the westward moving South American Plate and is being subducted under it. The belt of volcanoes along the Andes and the arc of volcanoes through Central America and Mexico are the direct results of this collision.
South of Easter Island the East Pacific Rise splits at another triple junction with the Chile Rise trending off to the east where is meets the subduction zone along the coast of southern Chile. The southern extension of the East Pacific Rise (called the Pacific-Antarctic Ridge, merges with the Mid-Indian Ridge at a triple junction south of New Zealand.
Along the East Pacific Rise the hydrothermal vents called black smokers were first discovered and have been extensively studied. These vents are forming volcanogenic massive sulfide ore deposits on the ocean floor. Many strange deep-water creatures have been found here. The southern stretch of the East Pacific Rise is one of the fastest-spreading sections of the Earth's mid-ocean ridge system.
