Plate Boundaries
The words "Plate Tectonics" derive from the Latin word tectonics and a Greek word tektovikoc which means to build. Together these words formulate a scientific theory that describes the large scale movement of the Earth's lithosphere. The lithosphere (Ancient Greek: λίθος [lithos] for "rocky", and σφαῖρα [sphaira] for "sphere") is the rigid[1] outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically to pressure that has built up over thousands of years. The lithosphere is broken up into tectonic plates or boundaries. On Earth, there are between seven and eight major plates and many minor plates. The relative movement that occurs, at the place where these plates meet, determines the type of boundaries that form: convergent, divergent, transform
Convergent Boundaries
Convergent boundaries, also known as destructive plate boundaries, are actively deforming regions where two (or more) plates or fragments of the lithosphere move toward each other and collide. When two plates move toward each other, they form either a continental collision or a subduction zone. The nature of the plate movements will be the factor that determines which is formed. In a continental collision or subduction zone, oceanic plates (crusts), move beneath other plates, which are either oceanic or continental plates (crusts). During the collision between two continental plates, large mountain ranges are formed, like the Himalayas. When the crust is affected by pressure, friction, and plate material melting into the mantle, earthquakes and volcanoes usually occur.
Divergent Boundaries
Divergent boundaries, also known as constructive boundaries or an extensional boundary, because of linear features (cracks) that exist between two tectonic plates that are moving away from each other. Divergent boundaries within continents form rifts at first, which grow into rift valleys. Usually, active divergent plate boundaries form between oceanic plates and exist as mid-oceanic ridges. Divergent boundaries also form volcanic islands, which occur when plates move apart to produce gaps which molten lava rises to fill.
Transform Boundaries
Transform boundaries, also known as conservative plate boundaries or faults, they do not create or destroy the crust of the Earth. They are a type of fault whose motion is mostly horizontal in either a sinistral or dextral direction. Transform faults have a distinct abrupt end. They are connected on both ends to other faults, ridges, or subduction zones. These faults are the only type of strike-slip fault that can be classified as a plate boundary. Transform faults are found on the ocean floor as valleys that may be even deeper than a rift valley of spreading ridges. Most transform faults are hidden in deep oceans where they form a series of short zigzag patterns that assist in the spreading of the seafloor, however, the best known and most destructive faults are those on land that are located at the margins of tectonic plates.
"Plate tectonics," 2012, p. 1)
"Plate tectonics," 2012, p. 1)
Images Source: Wheeling Jesuit University. (2004). Earth Floor: Plate Tectonics. Retrieved September 27, 2012 from: http://www.cotf.edu/ete/modules/msese/earthsysflr/plates1.html
References: Plate boundries. (2012). Retrieved from www.wikipedia.com
References: Plate boundries. (2012). Retrieved from www.wikipedia.com