PLATE MOVEMENT

The main reason that the earth's plates move is often the force of gravity, if a denser plate meets with another plate, it 'dives' underneath the other plate. This is called subduction. The sinking of this one plate underneath the other then causes the rest of the tectonic plate to be moved as well. The other reason for tectonic plate movement is due to convection currents that occur when mantle rocks near the core of the earth become heated, making them less dense than the upper mantle rocks. The warmer rocks then rise, while the cooler ones sink, this movement creates circulation within the mantle which can cause the plates to move.

Plate movements that cause earthquakes occur when energy inside the earth gets released with great pressure that it can cause the rocks and plates to break the earth's crust. An earthquake always originates at a focus point where the rocks have started to fracture. On the surface of the earth, above the focus point is the epicenter.

Shallow focus and deep focus earthquakes both are caused by the movements of the continental plates. Shallow earthquakes begin when the plates rub up against each other, they have their focus point nearer to the surface of the earth, but usually cause greater damage on the surface or on the earth's crust because they are more wide spread. Deep focus earthquakes occur when two tectonic plates move towards each other, which is followed by subduction (as mentioned above). Deep focus earthquakes occur when the collision of the two plates is more forceful.

Volcanism can also happen when tectonic plates move. When subduction occurs and a continental crust and oceanic crust collide, the oceanic crust moves underneath the continental crust. The sinking crust can sink so deep, that it can reach where it is hot enough for the crust to melt and release fluids that were inside. These fluids mix with the other materials in the earth and then create magma. The magma melts its way to the surface until it erupts and forms volcanic mountains.

Plate motion is known to be carried out by mantle convection, ridge push and slab pull. Mantle convection is when a current heats up a material, making it rise upward, as colder material falls downward. This creates an ongoing cycle that is also horizontal. As the material moves, it continuously pulls the plate with it, thus very slowly moving the plates. Mantle convection is also the cause of ridge push, which is when new material is pushed to the surface of the earth, breaking through to make a ridge, while driving the older material away. Ridge push also helps to create slab pull, which is when a tectonic plate is subducted underneath the crust, into the mantle. Why ridge push can help slab pull is because the new material produced by the ridge push is shoving the older material plate into another one. The more dense material is slid underneath the other one into the mantle. In other words, mantle convection, ridge push and slab pull are all forces that work together in creating plate motion.