Plate Boundaries
Continent and Ocean convergence -
A convergent boundary occurs when two plates are pushing toward each other. At some convergent boundaries, an oceanic plate collides with a continental plate. Oceanic crust tends to be denser and thinner than continental crust, the the oceanic crust gets bent and pulled under, or subducted, beneath the light and thick continental crust, this is called a subduction zone. The magma formed by the melting oceanic crust at the subduction zone rises up toward the earths surface and builds up magma chambers, where it feeds and created volcanoes on the overriding plate. Continent Convergence - When two continental plates collide a subduction zone does not form because the rock making up continental plates is generally lighter and less dense than oceanic rock, it is too light to get pulled under the earth and turned into magma. So when two continental plates collide a mountain range os formed. Mid Ocean Ridge - A divergent boundary marks two boundaries that are moving away from each other.Divergent boundaries in the middle of the ocean contribute to seafloor spreading. As plates made of oceanic crust pull apart, a crack in the ocean floor appears. Magma then oozes up from the mantle to fill in the space between the plates, forming a raised ridge called a mid-ocean ridge. The magma also spreads outward, forming a new ocean floor and new oceanic crust. Transform - At transform boundaries, tectonic plates are not moving directly toward of directly away from each other. Instead two tension plates grind past each other in a horizontal direction. Transform boundaries and the resulting faults produce many earthquakes because edges of tectonic plates are jagged rather than smooth. The edges of tectonic plates are jagged rather than smooth. As the plates grind past each other, the jagged edges strike each other, catch and stick, ‘locking’ the plates in place for a time. Because the plates are locked together without moving, a lot of stress builds up at the fault line. This stress is release in quick bursts when the plates suddenly slip into knew positions. The sudden movement is what we feel as the shaking and trembling of an earthquake. |