![]() ![]() Learning Designer: April Millet, The Pennsylvania State University Team Lead: Tim Bralower, Professor, The Pennsylvania State University. Hanegan, Research Assistant University of New Orleans, Li-San Hung, Research Assistant The Pennsylvania State University, Mark Kulp, Associate Professor University of New Orleans, Diane Maygarden, Research Associate University of New Orleans, David Retchless, Research Assistant The Pennsylvania State University, and Brent Yarnal, Professor The Pennsylvania State University, Tim Bralower, Professor The Pennsylvania State University. During the approximately 30 million years that the San Andreas boundary has been active, there have been approximately 550 kilometers of movement.Īuthors: Sean Cornell, Associate Professor Shippensburg University of Pennsylvania, Duncan Fitzgerald, Professor Boston University, Nathan Frey, Research Assistant The Pennsylvania State University, Ioannis Georgiou, Associate Professor, University of New Orleans, Kevin C. The San Andreas Fault of southern California is one of the most recognized transform boundaries where the Pacific Plate interacts with the North American Plate. Transform Boundaries: Transform boundaries exist where plates are sliding past, or more scientifically stated: shearing past one another. The Himalaya Mountains are actively building as the result of the compressional forces put upon the Indo-Australian Plate and the Eurasian Plate pushing against each other during the last 30 to 50 million years. Earthquakes, volcanoes, and mountains are often associated with convergent margins (see Illustration below of the three types of tectonic boundaries), and all three of these occur along the western edge of South America.Ĭontinent-Continent Boundaries: A continent-continent collision, or orogeny, occurs when two continental plates collide, fold, fault, and uplift, creating mountain ranges. This is a margin where the Nazca Plate is in direct contact with the South American Plate. For example, take another look at the global map of the tectonic plates, and you will notice that there is a boundary along the entire length of the western edge of South America. There are two types of convergent boundaries: continental-oceanic and continent-continent.Ĭontinental-Oceanic Boundaries: In the case of a continental-oceanic crust collision, the denser oceanic plate will fold or subduct underneath the less dense continental plate. Convergent BoundariesĬonvergent boundaries are those where plates are colliding with one another, forming either a subduction zone or continental collision. Divergent boundaries can also extend across continental crust – such as where the Arabian Plate is moving away from the African Plate and in the process creating the Red Sea Rift. Because the edges of the continents on opposite sides of the divergent boundary are considered tectonically inactive, they are called passive continental margins. It is referred to as the Mid-Atlantic Ridge because along this margin the oceanic crust is elevated and creates a ridge. At this location, new oceanic crust is forming (see Illustration of three types of tectonic boundaries) as underlying mantle material flows up through the gap created by the separation of the plates. This is a divergent boundary where the North and South American Plates are moving away from the African and Eurasian Plate. For example, if you look at the global base map again, you will see a plate boundary that extends all the way through the middle of the Atlantic Ocean. This is a boundary between two plates that are moving apart from one another. The result of these rigid plates moving around is the creation of one of three different types of plate boundaries: divergent, convergent, and transform boundaries. In the course of very long intervals of time, such as 100,000 years, these very slow rates of motion can add up to hundreds of meters or kilometers of total motion. As previously mentioned, these plates are not static, but, instead, move at very slow rates, averaging just a few centimeters per year. ![]() If you look very closely, you will also see that the margins of the plates are sometimes located on the edge of the continents, and sometimes the margins are located in the middle of the oceans. You will notice that the margins of the plates are very irregular and that the boundaries of the plates fit together similar to a jigsaw puzzle. Take a look at the global base map that shows, and identifies with labels, the different tectonic plates of the Earth. ![]()
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