~Introduction to Wilson Cycles~
In practice, science oscillates back and forth between Top-Down and Bottom-Up strategies. Newly discovered facts must naturally fit into a theory, and the theory must predict the existence of new facts. These strategies help bridge the gap between the study of individual rocks and grand theories such as plate tectonic theory.
Science begins with the study of individual phenomena - in the case of geology, minerals and rocks. We study rocks to understand the earth. From the study of our individual rocks we begin to build theories about what all these rocks mean, how they are related - to each other, and to the earth as a whole. We do this by induction. That is, we build our theories from the Bottom-Up by logically piecing together all the thousands of individual pieces (minerals and rocks) of the puzzle, until a theory of the earth's structure emerges. In the diagram below it has built up to the Six Tectonic Regimes that compose the lithosphere of the earth.
Once a theory is constructed, it becomes a powerful tool for understanding other parts of the earth. The theory tells us how everything is related by deductive logic to everything else. The theory also makes predictions about things we have not yet observed that would logically follow if the theory is true.
In the diagram below plate tectonic theory explains how the six tectonic regimes are logically related to each other and other parts of tectonic theory through the earth processes encompassed by the theory.
Thus, the complete diagram below shows how we can begin Top-Down or Bottom-Up and get to the same conclusions. Note that they come together in the Wilson Cycle
where the Six Tectonic Regimes
of the lithosphere can be said to have been constructed inductively from observation, or to exist logically through plate tectonic theory.
Plate tectonic theory as presented in these pages is only a top-down description. We still have to bridge the gap from the theory to the study of individual minerals and rocks, and bring the two together into a model that allows us to switch back and forth between the Bottom-Up and the Top-Down.
The Wilson Cycle
The Wilson Cycle is named after J. Tuzo Wilson who first made the connection between sea-floor spreading and subduction zones. The Wilson Cycle takes all the complex, multidimensional processes operating in a supercontinent Cycle and models them as the opening and closing of a single ocean basin. The Wilson Cycle brings together all the processes of plate tectonics, and all the processes by which individual rocks are generated, and uses them to tell a plausible story of how plate tectonic theory and individual minerals and rocks are related. Please go to the main page on the Wilson Cycle to learn more (Nine Stage Version).
Contributed by Lynn Fichter