CLARION FRACTURE ZONE

submarine fracture zone in the Earth's surface in the northeastern Pacific seafloor; 3,200 miles (5,200 km) in length, it was discovered by the U.S. Navy ship Serrano in 1949 and by the Scripps Institution of Oceanography's Mid-Pacific Expedition in 1950. The fracture zone extends along a global small circle, from its western end near a seamount group about 330 miles south of the island of Hawaii, to a point about six degrees of latitude farther north at the base of the continental slope off Puerto Vallarta, Mex. The continuation of the Clarion small-circle trend across southern Mexico is marked by a linear chain of 21 other active volcanoes. This has led some geologists to suggest that the Clarion Fracture Zone may extend into the Caribbean, inasmuch as the Cayman Trench between Cuba and Hispaniola also lies along the same general trend. Magnetic intensity variations of the seafloor along the Clarion Fracture Zone have not been mapped completely; however, the available data, together with the extraordinary length of the feature, suggest that it has been produced by seafloor spreading as the scar of transform faulting that began at least 80,000,000 years ago and that is still continuing at present.