Tectonic plates!!!

The Earth's surface is made up of a series of large plates and several minor plates. These plates, called tectonic plates, are always moving, generally about a few centimetres each year, which doesn’t sound that much at all really. Convection currents underneath the plates move them in different directions, this is because the ocean floors are always moving about, spreading from the centre and sinking at the edges. The edges of these plates, both minor and major, when they move against each one another, create earthquakes, volcanoes and even create mountains!

As the tectonic plates move, the world changes a little and sometimes a lot. About 200 million years ago, all the continents were one big piece of land called Pangea. Alfred Wegener, a German scientist, said that this one big piece of land slowly drifted apart, this was called continental drift. This was said in 1912 when the study of tectonic plates wasn’t around. (This theory also comes into play with the evolution of animals and humans. The ‘out of Africa’ theory for human evolution states man evolved in Africa then moved away to other parts of the world. They couldn’t do this if the world was separated as much as it is today, they didn’t have planes or ships to take them to other parts to the world. So it makes sense that the continents had to be much closer together for them to travel outside of Africa.)

http://www.moorlandschool.co.uk/earth/tectonic.htm

Three main types of boundaries exist between tectonic plates. 

The first is called a divergent boundary which occurs most often at mid-oceanic ridges. This is when two plates move away from each other, forming a break, or rift, in Earth's crust. Magma from the mantle (the middle section of the earth which is the deepest and very hot) rises up to fill the gap made from the separation of the plates, creating new crust. The results of this can be volcanic islands.

The second type is called a convergent boundary which happens when two plates move towards each other and meet. The plates that is made up of a more dense oceanic crust will often slide over the top of the plate that is made up of less dense oceanic crust. If both plates are made up of continental crust, very little subduction occurs. Instead, the plates buckle and fold to create valleys, ridges, and high mountain ranges such as the Himalayas.

The third type of boundary is called a transform boundary. At these locations, plates slide roughly alongside each other in opposite directions. The plates often get stuck as they move past each other, leading to a build-up of tension, which is ultimately released in the form of an earthquake. The more tension, the bigger the earthquake, if this occurs under water, tsunamis may occur.

http://www.teachersdomain.org/resource/ess05.sci.ess.earthsys.tectonic/