Letters in ovals are abbreviations for NPS sites listed above. In Mexico, a combinatiion of divergent and transform plate boundary motion is opening the Gulf of California, causing the Baja Peninsula to separate from the rest of Mexico. The San Andreas Fault is responsible for most of the movement in western California, causing a sliver of the state to slide past the rest of the continent. The Pacific Plate slides north-northwestward past the North American Plate along the San Andreas Transform Plate Boundary. They were lifted out of the ocean as part of the accretionary wedge of an ancient subduction zone. The sedimentary and metamorphic rocks across the fault line are similar to those found in Redwood National and State Parks on the North Coast of California. They have been transported about 300 miles (500 kilometers) in a north-northwestward direction along the transform plate boundary. The granite rocks in the foreground are similar to those found in Yosemite National Park in the Sierra Nevada Mountains. Tomales Bay is the surface expression of the San Andreas Fault, seen in the photo below. Point Reyes National Seashore, California. Lateral Movement along a Transform Plate Boundary Virgin Islands is located on another transform plate boundary, where the Caribbean Plate is sliding past the oceanic part of the North American Plate. The landscapes of Channel Islands National Park, Pinnacles National Park, Point Reyes National Seashore and many other NPS sites in California are products of such a broad zone of deformation, where the Pacific Plate moves north-northwestward past the rest of North America. Perhaps nowhere on Earth is such a landscape more dramatically displayed than along the San Andreas Fault in western California. The grinding action between the plates at a transform plate boundary results in shallow earthquakes, large lateral displacement of rock, and a broad zone of crustal deformation. Such boundaries are called transform plate boundaries because they connect other plate boundaries in various combinations, transforming the site of plate motion. Instead, blocks of crust are torn apart in a broad zone of shearing between the two plates. National Park Service lands contain not only active examples of all types of plate boundaries and hotspots, but also rock layers and landscapes that reveal plate-tectonic activity that occurred in the distant past.Where tectonic plates slip horizontally past one another, lithosphere is neither created nor destroyed. Transform plate boundaries are where plates slide laterally past one another, producing shallow earthquakes but little or no volcanic activity.Īnother large-scale feature is a hotspot, where a plate rides over a rising plume of hot mantle, creating a line of volcanoes on top of the plate.At a convergent plate boundary, one plate dives (“subducts”) beneath the other, resulting in a variety of earthquakes and a line of volcanoes on the overriding plate.Plates rip apart at a divergent plate boundary, causing volcanic activity and shallow earthquakes.There are three types of tectonic plate boundaries: The landscapes of our national parks, as well as geologic hazards such as earthquakes and volcanic eruptions, are due to the movement of the large plates of Earth’s outer shell. Katmai National Park and Preserve, Alaska. Active subduction along the southern Alaska coast has formed a volcanic arc with features including the Katmai caldera and neighboring Mount Griggs.
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