The triple junction offshore the west coast is created by which set of plates?

• A. Pacific plate, North American Plate, Gorda Plate
• B. Pacific plate, North American Plate, Juan de Fuca Plate
• C. Pacific plate, Nazca Plate, Gorda Plate
• D. Pacific plate, Australian Plate, North American Plate

Answer: (A)

A triple junction is where three tectonic plates meet. Offshore along the west coast, the Mendocino triple junction is the point where the Pacific plate, the North American plate, and the Gorda plate come together. The Gorda plate lies between the Pacific and North American boundaries in this region, so their edges intersect at a single junction. The Juan de Fuca plate is a separate microplate farther north and does not form this three-way intersection, and Nazca or Australian plates are located in entirely different regions.