Convergent, transform, AND DIVERGENT boundaries.CONVERGENT
When two plates hit each other, bits of the crust are destroyed and the plates become smaller. Results can vary if different types of plates are involved. A subduction is when oceanic and continental plates collide and the oceanic plate is forced under. When two oceanic plates hit, one will be pushed under, and magma from the mantle rises, forming volcanoes in the area. Where an underwater plate collides with another underwater plate, the more dense plate gives out and crumbles into the mantle. This action results in the partial melting of rock in the lithosphere, above the area of the subduction, causing underwater volcanoes to form. If the volcanoes become big enough to reach the surface, volcanic islands are formed. When two continental plates collide, mountains are created because the plates that are hitting each other push up, creating the mountains. They hit each other because of continental drift caused by earthquakes. The collision though is very slow because the continents only move a little bit each year. Alfred Wegener found out that the continents were drifting. TRANSFORM Transform is when two plate’s slide horizontally by each other. This was discovered in the 1960’s. Transform boundaries were discovered by a scientist named J. Tuzo Wilson. It will cause an earthquake when they slide by. A really famous transform boundary is the San Andreas fault. It was popularly thought that Los Angeles would crack off and fall into the ocean, but that was proven wrong. Although transform boundries are not marked by spectacular surface features but it causes lots of earth quakes. DIVERGENT Divergent Boundaries occur when the crust splits apart and magma from the mantle rises up and generates a new crust. When the lithosphere breaks apart, it breaks along parallel cracks that will tilt slightly outward from each other. During the plates separation along the boundary, the block between the crack cracks itself and falls down and into the Asthenosphere. As the block falls, it creates a rift (a valley) and then the magma goes through the crack and seals the space to create a new crust pushing the rest of the lithosphere farther. The plate separation is a slow process for example the Mid Atlantic Ridge causes the Atlantic Ocean to separate only 2 centimeters per year. It was discovered in the 1960's by Robert Dietz. |