OVERVIEW

The aim of this chapter is to introduce you to the subject of physical geography and to show that it is relevant to a wide range of important environmental issues. This chapter also presents the concept of systems: a framework for studying the earth's environmental processes that is used throughout the book.

• Physical Geography is the study of the earth's surface and of how and why it changes. Its focus is the life layer: the shallow surface layer where lands and oceans meet the atmosphere and where most forms of life are found.
• Processes affecting the earth's surface operate in four realms: the atmosphere, the lithosphere, the hydrosphere and the biosphere.
• The four realms and their processes can be studied at global, through continental and regional, to local scales.
• The processes of the four realms interact in the life layer to produce the environments of the earth's surface.
• A helpful way to understand the processes that shape the environments of the life layer is to study them as systems.
• Most natural systems are flow systems in which material (matter flow systems) or energy (energy flow systems) flows along pathways interconnected in a structure.
• All flow systems have a power source.
• Open flow systems have inputs and outputs, while closed flow systems do not.
• Cycles are closed matter flow systems. In a cycle, a fixed amount of material is continually recirculated through a series of pathways or loops.
• Feedback in a flow system occurs when the flow in one pathway affects the flow in another. Positive feedback increases flow while negative feedback reduces it.
• Negative feedback in a flow system tends to produce stability or equilibrium.
• Time cycles are periodic changes in system flow rates that occur over periods ranging from hours to millions of years.
• Studying the systems of the life layer and their interactions leads to a better understanding of the human habitat, environmental problems and global change.

KEY TERMS

physical          systems           open flow system   
geography         flow system       closed flow        
life layer        pathways          system             
atmosphere        structure         cycle              
lithosphere       input             material cycle     
hydrosphere       output            feedback           
biosphere         power source      equilibrium        
human habitat                       time cycle         

STUDY QUESTIONS

1. What is physical geography and what is its main object or focus of study?

2. Name and define the four great realms of the earth.

3. What is a flow system and what are its key components?

4. What is the difference between an open and a closed flow system? A matter and an energy flow system?

5. Give an example of a cycle that might be studied in physical geography and describe its operation in system terms.

6. Describe the concepts of feedback and equilibrium as they apply to systems. Illustrate your answer with an example of a natural system.

7. What is a time cycle as applied to a system? Give an example of a time cycle in a natural system.

8. Discuss the value of systems thinking for natural scientists.