This document introduces the key topics and learning objectives for a geography unit on the dynamic earth. It reviews the previous module, which focused on comparing more and less economically developed countries. It then outlines the four main physical spheres - air, water, life, and rocks - and how they operate as interconnected systems. The main themes of this unit are introduced: 1) the hydrological cycle and river basins, 2) ecosystems and vegetation biomes, and 3) atmospheric processes and climate change.