It is practical knowledge in the sense that we know why some parts of the world are inherently risky to live in. Even though volcanic eruptionis, earthquakes and tsunamis are difficult to predict, it makes sense to have building codes and emergency plans that take this into account.
It is science’s response to the beliefs that natural catastrophes (volcanism, earthquakes and tsunamis) are divine punishments for the evil ways of some individuals.
Even if you will never use or apply this knowledge, knowing about the theory of plate tectonics gives you a current scientific perspective on what we know about the natural world.
It is a good example of how scientific theories proceed by trying to fit several observations into a coherent explanation.
Learning about the observations that needed to be made and explained for the theory to win over scientists helps caution you against people who adopt belief systems without questioning the myths told to them, or those who try to profit from ignorance of how nature actually works.
When it is well taught, it should convince you that, like any scientific theory, plate tectonics is a “work in progress”. New discoveries continue to be made, and it takes creative and logical thinking, debate and a quest for more observations in order to determine which ones prove or challenge the current theory and which ones may lead to its refinement.
