Environmental Geography — Lesson 1
Plate tectonics is the unifying theory of Earth science that explains the distribution of geological features such as earthquakes, volcanoes, mountain ranges, and ocean basins. Earth's lithosphere is divided into approximately 15 major tectonic plates and several smaller ones. These plates move at rates of 1–10 centimeters per year. Plate boundaries are classified into three types: divergent, where plates move apart and new crust forms (e.g., mid-ocean ridges); convergent, where plates collide, leading to subduction, trenches, volcanic arcs, and mountain ranges (e.g., the Himalayas); and transform, where plates slide horizontally past each other (e.g., the San Andreas Fault).