Around 30 years ago, two things happened that were to revolutionize the understanding of our home planet. First, geologists realized that the continents themselves were drifting across the surface of the globe and that oceans were being created and destroyed. Secondly, pictures of the entire planet were returned from space. Suddenly, the Earth began to be viewed as a single entity; a dynamic, interacting whole, controlled by complex processes we scarcely understood. This Introduction explores emerging geological research and explains how new advances in the understanding of plate tectonics, seismology, and satellite imagery have enabled us to begin to see the Earth as it actually is: dynamic and ever changing.