ABSTRACT
Geography, like other academic disciplines, classifi es things in its attempt to understand how they work. e physical environment can be classifi ed in numerous ways, but one of the most commonly used classifi cations is that which breaks it down into four interrelated spheres: the lithosphere, the atmosphere, the biosphere and the hydrosphere. ese four basic elements of the natural world can be further subdivided. e lithosphere, for example, is made up of rocks that are typically classifi ed according to their modes of formation (igneous, metamorphic and sedimentary); these rock types are further subdivided according to the processes that formed them and other factors such as their chemical composition. Similarly, the workings of the atmosphere are manifested at the Earth’s surface by a typical distribution of climates; the biosphere is made up of many types of fl ora and fauna, and the hydrosphere can be subdivided according to its chemical constituents (fresh water and saline, for example), or the condition or phase of the water: solid ice, liquid water or gaseous vapour.
