The document outlines the theory of plate tectonics, detailing how the Earth's lithosphere is divided into plates that move independently over the mantle, with seismic activity primarily occurring at their boundaries. It discusses the importance of determining earthquake epicenters using triangulation and describes the three types of plate boundaries: divergent, convergent, and transform. Additionally, it explains geological effects associated with divergent boundaries, such as rift valleys and mid-ocean ridges, while also highlighting assessment questions to reinforce understanding.