The art and science of crystal chemistry lies in the interpretation of threedimensional electron and nuclear density data from diffraction experiments in terms of interatomic bonding and forces. With the exception of meticulous high-resolution studies (e.g. Downs 1983, Downs et al. 1985, Zuo et al. 1999), these density data reveal little more than the possible atomic species and their distributions within the unit cell. Other parameterizations of crystal structures, including atomic radii, bond distances, packing indices, polyhedral representations, and distortion indices, are model-dependent. These secondary parameters have proven essential to understanding structural systematics, but they are all based on interpretations of the primary diffraction data. <...>

Hillslopes occupy most of the land surface of the Earth. In areas of erosional topography the entire landscape, except the valley floors, consists of hillslopes. Consequently, hillslopes are a major focus of research in geomorphology. The study of hillslopes is essential not only in order to understand better the natural landscape but also for numerous practical reasons, such as controlling soil erosion and sedimentation on agricultural lands and mitigating the hazard posed by landslides. Geomorphologists have studied hillslopes since the latter part of the 19th century, but until the late 1950s their research focused almost exclusively on morphology. During the past 30 years, however, there has been a growing interest in hillslope processes, and today research on processes dominates this branch of geomorphology <...>

First, I describe what geology and paleontology aim to study. But in dealing with the history of life, we have to face the most difficult question first: where did Earth’s life come from? Astronomers find that organic compounds exist almost everywhere in space, yet we only know of life on one planet: Earth. I discuss the planets and moons of our solar system, and there are good reasons why none of them (except Earth) have life. Life exists in cells, so I discuss at length how complex organic molecules might have come together inside cells which survived, reproduced, and evolved on the early Earth. Laboratory experiments have already mimicked many of the steps in that process in the laboratory, but there is still a lot of work to be done. <...>