Physical Geography as a science is experiencing a radical change in philosophy. It is changing from a science that was highly descriptive to one that is increasingly experimental and theoretical. This transition represents a strong desire by Physical Geographers to understand the processes that cause the patterns or forms we see in nature, and to understand how these patterns and processes are influenced by (and in turn influence) human activity.
Before 1950, the main purpose of research in Physical Geography was the description of natural phenomena. Much of this description involved measurement for the purpose of gaining basic facts dealing with form (Geomorphology) or spatial appearance. Out of this research Physical Geographers determined such things as: the climatic characteristics for specific locations and regions of the planet; flow rates of rivers; soil characteristics for various locations on the Earth's surface; distribution ranges of plant and animal species; and calculations of the amount of freshwater stored in lakes, glaciers, rivers and the atmosphere. By the beginning of the 20th century Physical Geographers began to examine the descriptive data that was collected, and started to ask questions related to "why?" Why is the climate of urban environments different from the climate of rural environments? Why does hail only form in thunderstorms? Why are soils of the world's tropical regions nutrient-poor? Why do humid and arid regions of the world experience different levels of erosion?
In Physical Geography, and all other sciences, most questions that deal with "why?" are usually queries about process. To answer these questions, physical geographers must be familiar with and drawn upon other scientific disciplines, such as geology, meteorology, and oceanography. Some level of understanding about process can be derived from basic descriptive data. Process is best studied, however, through experimental manipulation and hypothesis testing. This requires the ability to utilize statistics and computer modeling. By 1950, Physical Geographers were more interested in figuring out process than just collecting descriptive facts about the world. This shift in emphasis was motivated by our growing need to understand how humans are changing the Earth and its environment. As a result, the standard undergraduate and graduate curriculum in Physical Geography exposes students to this type of knowledge so they can better ask the question "why?".