Wrangell (left) and Mt. Eurasia plate, Pacific plate, Africa plate, Caribbean plate, South America plate, Cocos plate, Juan de Fuca plate. St. Helens. , Divergent boundaries where two plates are moving apart. Four-letter codes indicate the ancient volcanic arc parks listed near the top of this page. When rifting of Pangea started at approximately 200 Ma, the fissuring was along a different line from the line of the earlier collision. 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The map shows the major tectonic plates that compose Earth's crust and upper mantle Arrows indicate direction of plate movement and the size of the arrows indicate rate of movement. Mazama, erupted and collapsed 7,700 years ago, forming the large cavity (caldera) that now holds Crater Lake. Some parks in the Sierra Nevada Mountains reveal igneous magma chamber rocks that represent the eroded remnants of an ancient subduction zone, when volcanoes similar to those found in the modern Cascade Mountains extended southward all the way through California. Is the Nazca Plate a convergent boundary? Mount Rainier National Park showcases a 14,411-foot (4,393-meter) composite volcano. Pangea, which existed from about 350 to 200 Ma, was not the first supercontinent. Before we talk about processes at plate boundaries, its important to point out that there are never gaps between plates. Plate Tectonics and Our National Parks (2020), Text and Illustrations by Robert J. Lillie, Emeritus Professor of Geosciences, Oregon State University [E-mail]. Mount Rainier is a 14,000 foot (4,300 meter) volcano in the Cascade Range developed above the place where the subducting Juan de Fuca Plate reaches sufficient depth to release hot fluids into the overriding North American Plate. The roots of ancient mountain belts, which are present along the eastern margin of North America, the western margin of Europe, and the northwestern margin of Africa, show that these land masses once collided with each other to form a mountain chain, possibly as big as the Himalayas. What caused the Chile earthquake of 1960? South America plate, Pacific plate, Antarctic plate, Cocos plate. The explanation is that plates move in a rotational manner. They contain explosive volcanoes formed as fluids rise from the top of the subducting plate and generate magma as they melt their way to the surface. This beauty is part of the reason that residents and visitors have learned to tolerate, and develop ways to mitigate, the effects of earthquakes, tsunamis and volcanic eruptionsbeasts that are consequences of the same tectonic forces that create the regions beauty. The Cascadia Subduction Zone, extending from northern California through western Oregon and Washington to southern British Columbia, is a type of convergent plate boundary. This plate includes the northeastern part of the Atlantic ocean, all of Europe, all of Russia (except its most eastern part), and down through southeast Asia, including China and Indonesia. Effects of the 1964 earthquake are quite spectacular in the park; the coastline dropped so much that in places it lies submerged beneath about 8 feet (2.5meters) of water. It runs along the north western coast of the United States and the southern British Columbia coast. 40 Million Years Ago To the north it borders the North American Plate, which encompasses the entire north of the continent. Rates of motions of the major plates range from less than 1 cm/y to over 10 cm/y. The Cascade Volcanoes extend in a north-south line from Mt. Similarly the South American Plate extends across the western part of the southern Atlantic Ocean, while the European and African plates each include part of the eastern Atlantic Ocean. Transform boundaries are places where plates slide sideways past each other. Feature labels. Layers of sand and mud, deposited on the ocean floor and later turned into the sedimentary rocks sandstone and shale, are seen above the pillows. Where tectonic plates converge, the one with dense, thin oceanic crust subducts beneath the one with thick, more buoyant continental crust. Usually, one of the converging plates will move beneath the other, a process known as subduction. Photo courtesy of Robert J. Lillie. This subduction forms the volcanoes of Guatemala, El Salvador, Nicaragua, and Costa Rica, also known as the Central America Volcanic Arc. The initial magma formed as mantle rock melts beneath a subduction zone has low silica (basalt) composition. That the Atlantic Ocean rift may have occurred in approximately the same place during two separate events several hundred million years apart is probably no coincidence. Over the next 50 million years, it is likely that there will be full development of the east African rift and creation of new ocean floor. The ocean area along southern Asia up to the India plate is also a part of the Australia plate. Many National Park Service sites are found in active and ancient subduction zones. Crater Lake in Crater Lake National Park partially fills the large depression formed when a composite volcano erupted and collapsed in on itself 7,700 years ago. Volcanic and metamorphic rocks exposed in Kenai Fjords National Park reveal the incredible forces that occur at an ocean/continent subduction zone. The two parallel mountain ranges influence many of the physical and cultural aspects of the Pacific Northwest. CC BY. There is tremendous deformation of the pre-existing continental rocks, and creation of mountains from that rock, from any sediments that had accumulated along the shores (i.e., within geosynclines) of both continental masses, and commonly also from some ocean crust and upper mantle material. This plate is rotating counter clockwise in towards the Pacific plate. Taiwan area is the collision boundary between the Philippine Sea plate and the Eurasia plate, which has complex interaction, attracting much attention[3033]. Mazama, Aniakchak spewed lava across its caldera floor for centuries after its collapse. North America plate, South America plate, Cocos plate. See Appendix 3 for Exercise 10.5 answers. When mixed with water from glaciers, snowmelt, and streams, these materials can make very dense, fast-moving volcanic mudflows (known sometimes by the Indonesian term lahar). This is what has happened in the Sierra Nevada of central and southern California, as represented by the granite-type rocks of Half Dome within Yosemite National Park shown on the California state quarter. It is suggested that this type of valley eventually develops into a linear sea (such as the present-day Red Sea), and finally into an ocean (such as the Atlantic). But thousands of eruptions over less than a million years have built Mount Rainier and other Cascade peaks to elevations of more than 10,000 feet (3,000 meters)! and Alberta are also a result of continent-continent collisions. The Pacific Plate is moving to the northwest at a speed of between 7 and 11 centimeters (cm) or ~3-4 inches a year. Geology This subduction-subduction-transform (SST) triple junction is referred to hereafter as the NACC triple junction. Igneous, sedimentary, and metamorphic rocks are all found in abundance. From 1999 to 2008, the United States Mint issued 25-cent coins representing each of the 50 states. But parks in the Cascade Mountains within the same subduction zone are dramatically different. Rainier were to suddenly and violently eruptso much that its magma chamber empties and the volcanic peak collapses in on itself. This situation may not continue for too much longer, however. The magma, which is lighter than the surrounding mantle material, rises through the mantle and the overlying oceanic crust to the ocean floor where it creates a chain of volcanic islands known as an island arc. The plate boundary is a broad zone of deformation with a width of about 60 miles (100 kilometers). A forearc basin develops in the low area between the two mountain ranges. The Coast Range and Cascades are the two parallel mountain ranges that form the Cascadia Subduction Zone in the Pacific Northwest. The volcanoes are forming above the region where the top of the subducting Juan de Fuca Plate reaches about 50 miles (80 kilometers) depth. Cocos Tectonic Plate Parks in the Cascadia Subduction Zone dramatically display the two distinct mountain ranges the Coast Range just above where the Juan de Fuca Plate begins to subduct, and the volcanic Cascade Range farther inland, where the top of the plate is deeper. Now you should see color coded lines that are the plate boundaries, and the names of Earth's major plates. As the basalt magma rises up through the thick continental crust of North America, it melts some of that rock, too. Observations. Modified from Oregon's Island in the Sky: Geology Road Guide to Marys Peak, by Robert J. Lillie, Wells Creek Publishers, 75 pp., 2017, www.amazon.com/dp/1540611965. Two arms of the triple junction can split to form an entire ocean. Mazama that formed Crater Lake. Adding TravelTime as Impedance in ArcGIS Network Analyst? This subduction-subduction-transform (SST) triple junction is referred to hereafter as the NACC triple junction. But given enough time, the Coast Ranges lift up distances we can measure, while at the same time wind, rain, and the pounding of waves wear the landscape back down. The North American plate is moving to the west-southwest at about 2.3 cm (~1 inch) per year driven by the spreading center that created the Atlantic Ocean, the Mid Atlantic Ridge. Along much of the boundary, the bulk of the motion occurs along the San Andreas Fault. The other piece became the Nazca plate.The Cocos plate also broke into two pieces, creating the small Rivera plate. An ancient volcano, Mt. The rising water melts rock in its path, forming a volcanic arc on the overrriding plate. Novarupta Lava Dome As fluid basalt lava flows into the ocean it forms a pile of globular structures known as pillows. In her version of the Oreo cookie demonstration, the creamy filling is the layers of sediment and basalt on the ocean floor. The southern boundary is a mid-oceanic ridge, the Galapagos Rise. It runs from the tip of South America eastwards to form a barrier between the Antarctic plate and the South America plate. Figure \(\PageIndex{4}\): Steven Earle. The eastern margins of North and South America and the western margins of Europe and Africa are called passive margins because there is no subduction taking place along them. Plate tectonics is the theory that the crust of the earth is broken up into giant slabs of rocks that sort of fit together like puzzle pieces. St. Helens, a lava dome later grew within the breached crater near the mountains summit. This plate is moving north west towards the Eurasia plate. To see the timing of these processes for yourself, go to time lapse of Continental Movements. Another divergent plate boundary is the East Pacific Rise, which separates the massive Pacific plate from the Nazca, Cocos, and North American plates. In this region, the Cocos Plate is subducting beneath the North America and Caribbean Plates (ocean-continent convergence), and the South and North America Plates are subducting beneath the Caribbean Plate (ocean-ocean convergence). Australia plate, Eurasia plate, Africa plate, Arabia plate. South America plate, Antarctic plate, Eurasia plate, North America plate, Arabia plate, India plate, Australia plate. Sandstone and shale layers at Kenai Fjords are commonly metamorphosed and were so deformed during subduction and uplift that they are vertical in places. On the western edge of the plate is a continuous subduction zone where the Cocos, Panama, and North Andean Plates are all converging with the Caribbean Plate. Today And at times, lower-silica components of their magma chambers erupt, producing basalt lava flows as well as cinders and volcanic bombs. At 20,625 square miles (53,396 square kilometers), Wrangell St. Elias National Park and Preserve is the largest U. S. national park six times the size of Yellowstone. The mountain is mainly andesite lava flows and volcanic mudflows covered by numerous glaciers. Compared to the other tectonic plates in the region, the Cocos Plate is converging with the Caribbean Plate at a steady rate of about 78 millimeters per year based on data from ISCO over 10 months. The major plates are Eurasia, Pacific, India, Australia, North America, South America, Africa, and Antarctic. About 200 million years ago a large tectonic plate (called the Farallon Plate) started to subduct beneath the western edge of North America. Find the plate boundary between the Juan de Fuca Plate (JF) and the North American Plate (NA). Silica-rich ash melted and coated the hot engine turbines with glass, causing all four of them to shut down. Pangea began to rift apart along a line between Africa and Asia and between North America and South America at around 200 Ma. Transform faults are not limited to oceanic crust and spreading centers; many of them are on continental margins. Illustrations above modified from Beauty from the Beast: Plate Tectonics and the Landscapes of the Pacific Northwest, by Robert J. Lillie, Wells Creek Publishers, 92 pp., 2015, www.amazon.com/dp/1512211893. The best example is the San Andreas Fault on the Pacific coast of the United States. This page titled 10.4: Plate, Plate Motions, and Plate Boundary Processes is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Steven Earle (BCCampus) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.
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