Read the definition. What word is defined?
The crust of the Earth is not one (even and regular) surface.
uniform
This is because two plates never (move quietly) past each other smoothly.
slide
The crust is broken up into many smaller (separate, not connected to other things) pieces called plates.
independent
This movement travels to the surface in waves that (cause the ground to move backwards and forwards).
shake the ground
The tiny movement of plates has (hard to believe) effects where the plates meet.
incredible
Small earthquakes are useful because they (set free, let go) the dangerous pressure between the plates.
release
Earthquakes tend to (happen) in regions where tectonic plates interact.
occur
Every few years, enough pressure builds up to produce a large earthquake, often with (causing enormous damage) results for human life and buildings in the affected area.
catastrophic
Earthquakes, however, tend to occur at the third kind of (edge of an area of land) – where plates slip alongside each other.
boundary
Afterwards the plates start moving once more until they get stuck again, and so the whole (series of events which lead to a change) starts over.
process