A divergent boundary exists when two plates are moving away from each other. This process can cause earthquakes, faults, or result in shield volcanoes.Divergent boundaries begin as rifts which over time become rift valleys. New crust forms from magma that rises to the Earth's surface between the two plates. Then, the rock solidifies, and becomes part of the plate. The two plates that move apart from the rift zone are mirror images of each other. The mid-Atlantic ridge (Iceland) and east African rift valley are examples of divergent plate boundaries.
Convergence - Subduction Ocean/Continent
When oceanic crust converges with continental crust, oceanic crust goes deeper because of it's higher density. This process is called subduction, and occurs at the oceanic trenches where the ocean meets the continent. This zone is known as the subduction zone.Subduction zones have a lot of intense earthquakes and volcanic eruptions. The subducting plate causes pressure in the mantle above the plate, and the magma rises and erupts, creating volcanoes. These coastal volcanic mountains are found in a line above the subducting plate. The volcanoes are known as volcanic arc, and can be found in Japan, North America, Andes, and Pacific Ring of Fire.
Convergence - Subduction Ocean/Ocean
The features of a subduction zone where an oceanic plate is subducting beneath another oceanic plate are the same as a ocean-continent subduction. An ocean trench marks the location where the plate is pushed down into the mantle. In this case, the line of volcanoes that grows on the upper oceanic plate is known as the island arc. When both plates are oceanic plates, they both have the same density, and therefore, neither one easily dives down. Over time, one will go into the mantle, and excess material works its way back to forma string of volcanic islands. The Philippines, Tonga Islands, and the Aleutian Islands are all ocean-ocean convergent plate boundaries.
Convergence - Collision Continent/Continent
Continent-continent convergence has created some of the world’s largest mountains ranges, such as Himalayas, Rockies, and Alps. These fold mountains have resulted from extended uplifting over millions of years creating a thick continental crust. Magma cannot penetrate this thick crust, so there are no volcanoes because the magma stays in the crust. Metamorphic rocks are common in this region asa result of the stress the continental crust experiences. With enormous slabs of crust smashing together, continent-continent collisions bring on numerous and large earthquakes.
Transform
Transform plate boundaries are locations where one plate slides past another plate. The fracture zone that forms a transform plate boundary is known as a transform fault, or strike-slip fault. Most transform faults are found in the ocean basin, and near the mid-ocean ridges. The San Andreas Fault in California is an example for transform fault. There is a lot of friction as the plates move past each other, when the plates get stuck, pressure builds, and major earthquakes can be the result. There are frequent earthquakes in California because of the transform fault there.
Hot Spots
A hot spot develops above a plume which allows magma to rise up to the service. Super heated plumes rise because of a crack in the lithosphere, and produces active volcanoes at the Earth's surface. Because of the tectonic plates are moving, the oceanic volcanoes move away from the hot spot. Then, they cool and subside, producing older islands, atolls, and seamounts. Hawaii has been created by being on a hot spot plate boundary.