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A Convergent Boundary is when plates serving land masses collide, and then the crust crumbles/buckles into mountain ranges. They can also occur where a plate of ocean dives, in a process called subduction, under a land mass. Ex:The Andes Mountain Range of western South America is another example of a convergent boundary between an oceanic and continental plate( continental to continental).Effects of a convergent boundary between an oceanic and continental plate include ( the Nasca Plate and Southern American Plate): a zone of earthquake activity that is shallow along the continent margin but deepens beneath the continent, sometimes an ocean trench immediately off shore of the continent, a line of volcanic eruptions a few hundred miles inland from the shoreline, destruction of oceanic lithosphere. Ex:30 to 50 million years in different stages the Indian Plate has collided with the Eurasian Continental Plate to form the Himalaya Mountains. The Himalaya system is the most common type of mountain formation, folded. They are created by tectonic plates pushing against each other and the only direction for these earth to move is up. At ocean to ocean convergences, one plat usually dives beneath the other forming deep trenches. Ex: Volcanic Island Arcs: When an oceanic plate sub duct under another oceanic plate, as the descending plate reaches depths of at least 100 Kms, ,magma is generated by the partial melting of asthenosphere. The magma moves upward to erupt as an island arc, a curved line of volcano that forms a string of Islands parallel to the oceanic trench. The rocks that occur in these island arcs are basaltic, andesitic and dacitic. (ocean to ocean)

In the oceans, magma from deep in the Earth's mantle rises toward the surface and pushes apart two or more plates, which is called the Divergent Boundary. This process renews the ocean floor and widens the giant basins. A single mid-ocean system connects the worlds oceans, making the ridge the longest mountain range in the world. Ex: The African plate is approximately 1/2 land mass with a diveProxy-Connection: keep-alive Cache-Control: max-age=0 ent plate boundary on the west edge running up through the Red Sea. The center of the plate is on land mass, but not in a good location. The African plate turns at a very slow counter-clockwise direction causing a lot of earth quake and volcanic activity on the west coast of Africa. The center of the plate would be too close to this area.Ex: The Juan de Fuca microplate system consists of a subduction zone along the North American plate at both the Gorda and the Juan de Fuca plates. The system meets the Pacific plate along a divergent zone at the east most boundaries. This divergent zone is composed of three major sea mount ridges (the Gorda, Juan de Fuca, and the Explorer ridges) which feed both the Juan de Fuca microplates to the west and the Pacific plate to the east. The divergent zone also doubles as a transform zone at the extension of the San Andreas lateral motion along the Mendocino, Blanco, and Sovanco Fracture Zones.Ex:The mid-ocean ridge is the world's longest mountain range, although it is submerged. It is a continuous ocean ridge that stretches through all the world's oceans, including the Pacific, Atlantic, Indian, Arctic, and Southern Ocean.





A divergent boundary is when two plates grind past each other along what are called strike-slip faults. They don't produce spectacular features like mountains or oceans too. Most are found on the ocean floor. Commonly offset the active spreading ridges, producing zig-zag margin and generally defined by shallow earthquakes. They also have a halting motion triggers large earthquakes. One earthquake devastated San Francisco in 1906. Ex:The Puerto Rico Trench is an oceanic trench located on the boundary between the Caribbean Sea and the Atlantic Ocean. The trench is associated with a complex transition between the subduction zone to the south along the Lesser Antilles island arc and the major transform fault zone or plate boundary that extends west between Cuba and Hispaniola through the Cayman Trench to the coast of Central America. Ex: The San Andreas Fault is the sliding boundary between the Pacific Plate and the North American Plate. It slices California in two from Cape Mendocino to the Mexican border. San Diego, Los Angeles and Big Sur are on the Pacific Plate.Ex:The Muray Fracture Zone is another example. It is fromed from the pacific and Juan De Fuca Plates. Faults and fracture zones are often found in the ocean floor because of Transform Boundaries. The fractures are typically zig zag.

Citations

http://www.zetatalk.com/info/tinfo05r.htm. 19 Nov. 2009. Web. 1 Jan.

http://www.soest.hawaii.edu/GG/ASK/plate-tectonics2.html. 19 Nov. 2009. Web. 1 Jan.

http://www.colorado.edu/GeolSci/Resources/WUSTectonics/PacNW/juan_de_Fuca_general.html. 19 Nov. 2009. Web. 1 Jan.

http://science.nationalgeographic.com/science/earth/the-dynamic-earth/plate-tectonics-article.html. 19 Nov. 2009. Web. 1 Jan.

http://school.nettrekker.com/authenticate/ipauth/1?np=/home.ftl&pp=/ipauth_error.ftl. 19 Nov. 2009. Web. 1 Jan.

http://www.wisegeek.com/what-is-the-mid-ocean-ridge.htm. 19 Nov. 2009. Web. 1 Jan.