What tells you that earths surface is divided into a dozen or so slow moving plates or pieces?

The Earth's surface is divided into a dozen or so slow-moving tectonic plates, which is supported by evidence such as the distribution of earthquakes and volcanic activity along plate boundaries. Additionally, the concept of plate tectonics explains the fit of continents, like how South America and Africa appear to match. Geological features, such as mountain ranges and oceanic trenches, also indicate the movement and interaction of these plates over time. Satellite measurements further confirm the gradual movement of these plates, typically a few centimeters per year.