exam question 7 plate tectonics

It has become commonly known in recent years that the surface of the earth is floating on a giant pool of liquid hot magma. This is explained by a concept known as plate tectonics.
Plate tectonics states that the earth is made up of several different and seperate plates. These plates are floating on molten rock far under the ground. This concept explains things such as earthquakes, volcanoes, rifts in the earth, and other motion of the earth's surface.
The outermost part of the Earth's interior is made up of two layers: above is the lithosphere, comprising the crust and the rigid uppermost part of the mantle. Below the lithosphere lies the asthenosphere. Although solid, the asthenosphere has relatively low viscosity and shear strength and can flow like a liquid on geological time scales. The deeper mantle below the asthenosphere is more rigid again. This is, however, due not to cooler temperatures but to high pressure (http://en.wikipedia.org/wiki/Plate_tectonics).
The tectonic plates of the lithosphere float on the viscous rock of the asthenosphere. Moving plates can cause occurances felt by humans on the earth's surface in one of three ways: convergence, divergence, and transformation. These are the actions that cause earthquakes, volcanoes, and other such occurances.
Transformation is the lateral sliding of two plates past each other. When the plates get "caught" on each other, they build up kinetic energy. When this energy is released, it causes earthquakes. An example of this is the San Andreas Fault, on the western coast of North America.
Divergence is the process of tectonic plates moving apart from each other. When this happens, magma from under the earth's crust forces itself up under immense pressure, creating a "hotspot". Divergent movement can also cause the formation of underwater rifts, such as the Mid-Atlantic Ridge.
Convergence is the opposite of divergence. It is the colliding of two plates together. When the two plates collide, one is forced down and the other is forced up creating mountains or volcanoes. An example of convergence is the Cascade Mountain Range in North America (http://en.wikipedia.org/wiki/Plate_tectonics).
The three types of volcanoes that are formed from plate shifting are shield volcanoes, stratovolcanoes, and cinder cones.
Shield volcanoes are fromed from divergence forcing lava up and spreading out to form a wide, flat volcano. Stratovolcanoes are formed by convergence making a mountain come up and forcing lava to flow out. Cinder cones are formed from volcanoes shooting out ashes and cinder, which builds up around the mouth of the volcano.