Forces in the Earth cause its surface to change over time.
![Picture](/uploads/4/2/9/3/42931405/2980112.png?250)
There are 3 types of stress.Tension,Compression,and Shearing.Tension is when 2 plates are seperated by a pulling force.When they are heading in 2 different directions and new crust is being formed.Another type of stress is called Compression.That is when 2 faults come together.Shearing is when 2 plates move against each other,but it isn't like Tension.The two plates are pulling in the other direction.If you don't understand what I mean then look at the diagram and maybe you will understand then.
This is a diagram of the boundaries. There are 3 types of boundaries, Tension,Compression,and Shearing.