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.
