Plate tectonics refers to the theory that the Earth's crust is composed of large rigid plates that slowly move over the mantle. There are 7 major and many minor tectonic plates that are constantly changing through processes like combining, becoming crushed, or being subducted beneath another plate. When the plates shift it can cause earthquakes, tsunamis, elevation changes to land, and structural damage costing lives and property. Scientists are working to better predict plate shifts but preparing for possible impacts through building codes and emergency plans is currently the best approach.