Plate tectonic history of the northeast Pacific and western North America
In the present configuration of tectonic plates, the northeast Pacific region is dominated by the huge Pacific Plate. Along its eastern edge, the Pacific Plate presently interacts with two medium-sized oceanic plates, the Juan de Fuca and Cocos Plates, and a few related small platelets: the Yakutat, Explorer, South Gorda, and Rivera Plates (Fig. 1). All of these occupy relatively small regions along the edge of the Pacific Plate, interacting as well with the North American Plate along its western rim.
The most complex modern plate boundaries in the northeast Pacific region occur where the eastern edge of the Pacific Plate abuts directly against North America. These are primarily strike- slip boundaries with subordinate amounts of extension: the Queen Charlotte-Fairweather fault system, including the oblique motion of the Yakutat block, and the San Andreas fault system, including the oblique extension in the Gulf of California. The diffuse nature of the earthquake zones around these features, depicted in Figure 1, shows that plate boundaries within the continental lithosphere are not as narrow and simple as those within the oceanic plates. The broad zones of activity in the Great Basin show the existence of at least two diffuse inland zones of deformation, as well.
Figures & Tables
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.