Folds where N.A. plate hits Juan de Fuca Plate
The collapse that sent these huge chunks tumbling down the slope was most likely triggered by an earthquake. Such dramatic failures of the continental slope can generate violent tsunamis that may inundate the coast nearby or travel across the Pacific and create havoc on distant shores.
FOLDED CARPET of sediments covers the seafloor offshore of Oregon. The undulations result from the head-on collision between the North American and Juan de Fuca plates. Like a colossal bulldozer, the North American Plate scrapes sediments off the down-going Juan de Fuca Plate and piles them into folds. To the north (lower left), the folds of sediment form distinct ridges. To the south (upper right), where part of the Juan de Fuca Plate breaks through its sedimentary cover, the folds are stacked so closely that they form terraces.