Plate tectonics theory

Plate tectonics is a relatively new theory that has revolutionized the way geologists think about the Earth. According to the theory, the surface of the Earth is broken into large plates. The size and position of these plates change over time. The edges of these plates, where they move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes, and mountain building. Plate tectonics is a combination of two earlier ideas, continental drift and sea-floor spreading. Continental drift is the movement of continents over the Earth's surface and in their change in position relative to each other. Sea-floor spreading is the creation of new oceanic crust at mid-ocean ridges and movement of the crust away from the mid-ocean ridges.

The Theory of Continental Drift has had a long and turbulent history since it was first proposed by Alfred Wegener in 1910. Vigorously challenged yet widely ignored, the theory languished for half a century, primarily due to its lack of a plausible mechanism to support the proposed drift. With the discovery of sea-floor spreading in the late 1950's and early 60's, the idea was reinvigorated, this time as the Theory of Plate Tectonics.

Plate tectonics is now almost universally accepted, its mechanisms plausible and to a degree demonstrable. However, many details of the mechanism are yet to be worked out, and many theories involving various details of plate tectonics rest on some questionable assumptions. This set of pages attempts to define some of the basic principles of the mechanism, and to examine their effect on the creation of landforms.

What follows is NOT a summary of the current thinking about plate tectonics and its mechanisms; rather, many new, and probably highly controversial, ideas are presented for consideration. What IS presented is a broad analysis of the basic principles that should apply to the movements of plates, some new hypotheses about how they apply to convection and landform formation, and some expected scenarios for differing tectonic events.

For those unfamiliar with the theory of plate tectonics, a separate page - The Basics of Plate Tectonics - is provided. This summary offers a brief condensation of the basic principles of Plate Tectonics. A much more comprehensive explanation of Plate Tectonics can be found on the USGS Web Site.

http://webspinners.com/dlblanc/tectonic/ptABCs.php