![]() ![]() Point Reyes National Seashore, Golden Gate National Recreation Area, and Pinnacles National Park present landscapes affected by the main line of movement, the San Andreas Fault. Modified from “Earth: Portrait of a Planet, by S. 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. The San Andreas Fault is one of the best examples of lateral plate motion.Where tectonic plates slip horizontally past one another, lithosphere is neither created nor destroyed. When two tectonic plates slide past each other, the place where they meet is a transform or lateral fault. This can lead to the formation of huge, high mountain ranges such as the Himalayas. Since neither plate is stronger than the other, they crumple and are pushed up. About 80% of earthquakes occur where plates are pushed together, called convergent boundaries.Īnother form of convergent boundary is a collision where two continental plates meet head-on. Sometimes the molten rock rises to the surface, through the continent, forming a line of volcanoes. The rocks pulled down under the continent begin to melt. Subduction causes deep ocean trenches to form, such as the one along the west coast of South America. When a continental plate meets an oceanic plate, the thinner, denser, and more flexible oceanic plate sinks beneath the thicker, more rigid continental plate. The Great Rift Valley in Africa, the Red Sea and the Gulf of Aden all formed as a result of divergent plate motion.Ĭonvergent (Colliding): This occurs when plates move towards each other and collide. The earthquakes that occur along these zones, called spreading centers, are relatively small. Molten rock from the mantle erupts along the opening, forming new crust. The three main types of plate movements include:ĭivergent (Spreading):This is where two plates move away from each other. The movements of the plates help shape the geological features of our planet. Other plates include continents, and some plates include both continents and ocean. Some of the plates have ocean water above them. When the plates finally give and slip due to the increased pressure, energy is released as seismic waves, causing the ground to shake. Most seismic activity occurs at three types of plate boundaries-divergent, convergent, and transform.Īs the plates move past each other, they sometimes get caught and pressure builds up. ![]() Movement in narrow zones along plate boundaries causes most earthquakes.
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