Today the term plate tectonics is not only familiar to scientists, it is entering everyday language and finding its way into dictionaries. The resulting transformation of the way in which we regard the Earth has brought about a reappraisal of the vast accumulation of information about the surface of the Earth collected by geographers, geologists, oceanographers and others over the centuries, reviewing and reinterpreting that information in the comprehensive new framework provided by the new plate tectonic concept. But more than that, this revolution has brought about a change of approach in the scientific study of the Earth. No longer is geology a secondrate descriptive science-it has joined forces with the physical sciences in a new and more cohesive whole to which the term Earth sciences is now so much more appropriate. <...>

Earth is a dynamic planet that has changed continuously during its 4.6 billion years of existence. The size, shape, and geographic distribution of the continents and ocean basins have changed through time, as have the atmosphere and biota. As scientists and concerned citizens, we have become increasingly aware of how fragile our planet is and, more importantly, how interdependent all of its various systems and subsystems are.
We also have learned that we cannot continually pollute our environment and that our natural resources are limited and, in most cases, nonrenewable. Furthermore, we are coming to realize how central geology is to our everyday lives. For example, on March 11, 2011, a magnitude 9.0 earthquake struck Japan, killing more than 20,000 people and generating a tsunami that wreaked destruction along the coast of northeastern Japan, as well as damaging three nuclear power plants and causing radioactive leakage in one of them.

Earth is a dynamic planet that has changed continuously during its 4.6 billion years of existence. The size, shape, and geographic distribution of the continents and ocean basins have changed through time, as have the atmosphere and biota. As scientists and concerned citizens, we have become increasingly aware of how fragile our planet is and, more importantly, how interdependent all of its various systems and subsystems are.

There have been two dominant models used in describing the chemical and electronic behavior of a surface. One is the atomistic model, or the “surface molecule” model; the other is the band model, often called for emphasis the “rigid band” model. The atomistic model has been preferred in general in discussions of the chemical processes at a solid surface; the rigid band model is often preferred in discussions of electron exchange between the solid (especially a semiconductor) and a surface group, where, for example, the conductivity of the solid is changed.