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. <...>

Progradation of Atchafalaya Delta, one of the most dynamic geological events of the century, has produced a sizable new sand body on the Louisiana coast. Evolution of depositional environments in Atchafalaya Bay has been determined from analysis of sediment cores and bathymetric surveys. Use of X-ray radiography has made possible recognition of a number of subenvironments within major environments. Atchafalaya Delta exhibits all the sedimentary environments recorded in earlier Mississippi delta lobes. However, excellent stratigraphic control and current knowledge of the processes of deposition in Atchafalaya Bay make it possible to better link process-response in this than in other Mississippi subdeltas. In contrast to the modem Mississippi subdelta, the Atchafalaya should prograde more rapidly, form thinner sand bodies, and eventually cover a wider area, much like the Lafourche, St. Bernard, and Teche delta lobes. <...>

You are beginning a study of geology—the science of Earth. Your goal is to learn how Earth works. Along the way, you will learn about the importance of geology to humans. You will consider the origin of essential resources and the forces that drive geologic processes that are hazardous to our lives and livelihoods. This text is not simply a collection of facts to memorize. It is an invitation to think about how scientists use creativity, diligence, and technology to arrive at the current body of knowledge about Earth <...>

Life appeared in the oceans in a past so distant that it is diffi cult to imagine. The exact age of life on Earth is debated because the structures once considered to represent the oldest fossils (remains of ancient organisms, or traces which they left) have been reinterpreted as mineral crystallization in microscopic fractures by some paleontologists (this reinterpretation is itself debated). The fi rst life forms were very simple and resembled extant bacteria, some of which formed stromatolites, the oldest of which are about 3 Ga (billion years) old (Fig. p.1). Stromatolites are still being formed today in some coastal regions. For at least 1.5 Ga, life remained in its native aquatic environment. Thus, for the greatest part of the history of the biosphere, life remained in water, diversifi ed, and radiated into several ecological niches. The oceans and seas teemed with life well before the fi rst animal ventured out of the water. <...>