Each plate shifts somewhere between 0 and 10 mm annually. Parks near the coast, including Point Reyes National Seashore, Golden Gate National Recreation Area, and Pinnacles National Park, contain volcanic and plutonic rocks that were plucked from the edge of the North American Plate and transported tens to hundreds of miles northwestward as part of the Pacific Plate. These observations about the distribution of earthquakes and volcanoes helped geologists define the processes that occur at spreading ridges and subduction zones. Photo courtesy of Robert J. Lillie. On the east, the North American Plate is subducting westward, forming volcanoes of the Lesser Antilles Island Arc. Like many of the rocks that are caught up in the zone of transform motion between the Pacific and North American plates, the rocks at Channel Islands National Park were deformed as part of the accretionary wedge during earlier subduction of the Farallon Plate. These are also known as compressional or destructive boundaries. The broad zone of transform motion between the Pacific and North American plates formed numerous slivers of mountain ranges with narrow valleys in between. Modified from “Earth: Portrait of a Planet, by S. Marshak, 2001, W. W. Norton & Comp., New York. The plate boundary is a broad zone of deformation with a width of about 60 miles (100 kilometers). Feature labels. Similarly, if the same situation occurred and the fault was left-lateral, the tree would appear to move left. Is the Coronavirus Crisis Increasing America's Drug Overdoses? A plate boundary is a location where two tectonic plates meet. California’s sheared-up landscape and earthquake hazards reflect the movement of the Pacific Plate past the edge of North America along a transform plate boundary that extends from the Mexican border to north of San Francisco. Earthquakes on the San Andreas Fault can greatly upset cities along its length, including the San Diego, Los Angeles, and San Francisco/Oakland areas. Convergent boundaries are home to some of the largest geologic features on the planet including mountain ranges, volcanoes, oceanic trenches and island arcs. Some examples of include the Andes Mountains, the “Ring of Fire”, and the ancient Sierra Nevada batholith. ii. Occasionally one plate forces the other down to form an underwater sea trench. The 16 feet (about 200 inches, or 5 meters) of offset along the fence line thus carries a powerful message. Deformation along the transform plate boundary in California can be visualized by placing a deck of cards between your hands in a praying position. NP = National Park Imagine that your left hand is the undeformed Pacific Plate, your right hand the intact North American Plate. For western California, each slipping card face would be a fault surface. In particular, bends along strike-slip faults can form both basins and mountains like those shown in the image above. Photo courtesy of Robert J. Lillie. The earthquake ruptured a large portion of the San Andreas Fault, including land that is now Point Reyes National Seashore and Golden Gate National Recreation Area. Every century or so a large earthquake is necessary to release stress accumulated along large segments of the San Andreas Fault that lock rather than slip smoothly. The long mountain ridges and narrow bays in the region surrounding U. S. Virgin Islands National Park are a product of compression due to the convergence, in addition to lateral motion due to shearing along the transform plate boundary. The cumulative movement within the broad San Andreas transform plate boundary has had dramatic effects on a landscape that initially developed as part of an ocean/continent subduction zone. Thousands of earthquakes over millions of years have built this landscape not only along the major fault line—the San Andreas Fault—but also on other faults within the broad zone of shearing between the Pacific and North American plates. Instead immense collisional forces and large thrust faults form in response uplifting large mountain ranges like the Himalaya. Will 5G Impact Our Cell Phone Plans (or Our Health?! These plate boundaries can occur both within continents and under oceans. Depending on the type of boundary, the interactions of tectonic plates can cause earthquakes, volcanic activity, or mountain-building. Divergent plate boundaries often occur under the ocean. Convergent plate boundaries are home to the deepest and largest earthquakes on the planet. Strong earthquakes and the volcano formation are common as plates clash at a convergent boundary. @2018 - scienceterms.net. Sometimes the valleys are partially filled with water, as at Point Reyes National Seashore, where Tomales Bay and Olema Valley follow the main trace of the San Andreas Fault. Virgin Islands National Park. Rocks have been disrupted by shearing and other forces associated with the transform plate motion and, in some instances, transported northward a long distance from where they originally formed. Tectonic plate interactions are classified into three basic types:. As mentioned above, transform boundaries are common along divergent plate boundaries where they connect sections of oceanic spreading centers or mid-ocean ridges, helping create some of the longest topographic features on the planet. Both plates are capped by oceanic crust. Some examples of divergent plate boundaries include the mid-Atlantic ridge, the east Pacific rise and the east African rift. This feature includes the famous San Andreas Fault, responsible not only for destructive earthquakes, but also for the spectacular scenery of the San Francisco Bay area and other coastal regions of California. Point Reyes National Seashore and Golden Gate National Recreation Area are the only two NPS sites that are right on the San Andreas Fault. NRA = National Recreation Area These forces also create a sheared-up landscape that includes spectacularly beautiful coastlines and economically important harbors. N&SP = National and State Parks Volcano - Volcano - Volcanoes related to plate boundaries: Topographic maps reveal the locations of large earthquakes and indicate the boundaries of the 12 major tectonic plates. Parks in western California contain blocks of crust that have moved great distances north-northwestward along the San Andreas Fault. Beginning about 30 million years ago, so much of the Farallon Plate was consumed by subduction that the Pacific and North American plates were in contact, forming the San Andreas transform plate boundary in western California. Point Reyes National Seashore and Joshua Tree National Park have granitic magma-chamber rocks of the eroded arc, and Pinnacles National Park preserves volcanic rocks. Channel Islands National Park, Santa Monica Mountains National Recreation Area and Joshua Tree National Park are within the Transverse Ranges, a block of crust that rotated as a result of the shearing motion. Photo by Robert J. Lillie. The Sierra Nevada are the eroded remnants of the volcanic arc developed when the Farallon Plate subducted beneath the continent. Festival of Sacrifice: The Past and Present of the Islamic Holiday of Eid al-Adha. There are three different types of tectonic plate boundaries, which are defined by the relative motion of each plate. At a convergent boundary two plates move towards each other. The cards slip along their faces, forming a broad zone of shearing between your unaffected hands. These plate boundaries can occur both within continents and under oceans.

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