The Middle America Trench extends for roughly 3,000 km from the Tres Marias Islands off Mexico near the mouth of the Gulf of California southward to the Osa Peninsula in southwestern Costa Rica (Fig. 1 and Plate 1C). The Tamayo Fracture Zone, a transverse fracture zone associated with the East Pacific Rise, bounds the trench to the north, and the Panama Fracture Zone bounds it to the south. The Tehuantepec Ridge separates the trench into northern and southern segments, each having different and contrasting morphological and structural styles.Convergent plate boundaries, such as the Middle America Trench, constitute a complicated family of structural zones characterized by high relief, intense deformation, large earthquakes, and often by extensive volcanism. The study of modern convergent plate boundaries contributes not only to an understanding of contemporary and recent processes, but of ancient plate boundaries and mountain belts as well.
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This new synthesis includes a section on plate kinematics, documenting the basis for a new interpretation of the magnetic anomaly patterns. It also includes: six chapters on various aspects of tectonics, petrologic characteristics, and hydrothermal processes of active ridges from the Galapagos Rift to the Juan de Fuca Ridge; a section on mid-plate volcanism, including the Hawaii-Emperor chain; five chapters on various aspects of northeastern Pacific sedimentary regimes; and nine chapters on the geology of the Pacific continental margin from the Aleutians to Guatemala, seen from the perspective of marine geology. Three separate oversize plates illustrate the bathymetry of the northeast Pacific; two more on the same base show distribution of sediment samples and types and magnetic anomaly data and tectonic interpretations; and others include a synthesis of the geology and bathymetry of the Hawaiian Islands, details of bathymetry along parts of the East Pacific Rise, and a major seismic profile across the Pacific margin of Guatemala.