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This chapter discusses the history of atmospheric oxygen through geologic time. One of the giants in this discussion is Vladimir Vernadsky 1863–1945), a Ukranian mineralogist turned geochemist and visionary thinker. In 1926 he published his magnum opus The Biosphere, in which he systemically explored how life works as a geological force. One subject he touched upon was the history of atmospheric oxygen. He initiated this discussion by stating that in all geological periods, the chemical influence of living matter on the surrounding environment has not changed significantly. He concluded that the phenomena of superficial weathering clearly show that free oxygen played the same role in the Archean Era that it plays now. The chapter then explores early Earth biology, focusing on signs of cyanobacteria, without which oxygen could not have accumulated into the atmosphere.

This chapter provides an introduction to fossils and a geologic time frame, which provides a context for interpreting marine mammal fossils and possible causes for their origin and diversification. The evolution of marine mammal communities through space and time are considered, as well as what may have led marine mammals back to the sea. The use of stable isotope technology is explored for ecologic studies that range from reconstructing paleotemperatures and climate change to documenting diet and foraging ecology among both living and fossil marine mammals.

This essay reviews the book Annals of the Former World, by John McPhee. First published in 1998, Annals of the Former World presents a geological history of North America. The book is a compilation of writing on geology McPhee began in 1978 when he published a short item about a road cut on Interstate 80 west of New York City. Over the following twenty years, that initial story led McPhee to make a series of trips across America in the company of geologists, through whom he would explore both the geologic history of a region and the history of geology itself. Those travels resulted in four separate books: Basin and Range, In Suspect Terrain, Rising from the Plains, and Assembling California. For the publication of Annals of the Former World, these were joined by a fifth and final section, Crossing the Craton. McPhee invokes the notion of “animal time”—as opposed to geologic time—to illustrate how humankind stands in relation to the larger sweep of events.

This chapter explores the host of mechanisms involving biological and physical processes in the context of the evolution of ocean chemistry on geologic time scales. Large fluctuations in the salinity of the ocean are unlikely to have occurred, although periods following the deposition of evaporite “giants” may have been anomalously low in salinity. The Ca concentration and alkalinity of the ocean are regulated by the sensitive response of the ocean’s calcium carbonate compensation depth to variations in the oceanic C_aCO₃ saturation state. Potential metal toxicity is prevented by the production of specific metal-binding ligands by the marine biota. Overall, the system is resilient, but human activity may be perturbing important state variables of the ocean to an extent that will be detrimental to marine life.

This chapter examines scientific ideas that led to the theory of deep time, with particular emphasis on the work of William Thomson, later Lord Kelvin. Kelvin used the laws of physics to reject Charles Lyell's theory of uniformitarianism to explain an eternal, unchanging Earth. The first law of thermodynamics holds that in any process, energy in the form of heat and work is conserved. The second law can be stated simply as: heat flows spontaneously from hotter to colder places, never the opposite. In describing geologic time as infinite and the Earth as unchanging, Lyell claimed that the Earth is a perpetual-motion machine, one that can not only win the energy battle but go on doing so forever. But the first and second laws of thermodynamics prove that such a machine is impossible. According to Kelvin, Lyell's theory “violates the principles of natural philosophy.” This chapter considers Kelvin's argument about the age of the Earth and how he pushed geology toward the twentieth century.

Of the estimated one to four billion species that have existed on the Earth since life first appeared here (Simpson 1952), less than 50 million are still alive today (May 1990). All the others became extinct, typically within about ten million years (My) of their first appearance. It is clearly a question of some interest what the causes are of this high turnover, and much research has been devoted to the topic (see, for example, Raup (1991a) and Glen (1994) and references therein). Most of this work has focussed on the causes of extinction of individual species, or on the causes of identifiable mass extinction events, such as the end-Cretaceous event. However, a recent body of work has examined instead the statistical features of the history of extinction, using mathematical models of extinction processes and comparing their predictions with global properties of the fossil record. In this book we will study these models, describing their mathematical basis, the extinction mechanisms that they incorporate, and their predictions. Before we start looking at the models however, we need to learn something about the trends in fossil and other data which they attempt to model. This is the topic of this introductory chapter. Those well versed in the large-scale patterns seen in the Phanerozoic fossil record may wish to skip or merely browse this chapter, passing on to chapter 2, where the discussion of the models begins. There are two primary colleges of thought about the causes of extinction. The traditional view, still held by most palaeontologists as well as many in other disciplines, is that extinction is the result of external stresses imposed on the ecosystem by the environment (Benton 1991; Hoffmann and Parsons 1991; Parsons 1993). There are indeed excellent arguments in favor of this viewpoint, since we have good evidence for particular exogenous causes for a number of major extinction events in the Earth's history, such as marine regression (sealevel drop) for the late-Permian event (Jablonski 1985; Hallam 1989), and bolide impact for the end-Cretaceous (Alvarez et al. 1980; Alvarez 1983, 1987).

The boreal forest occupies 10% of the ice-free terrestrial surface and is the second most extensive terrestrial biome on Earth, after tropical forests (Saugier et al. 2001). It is a land of extremes: low temperature and precipitation, low diversity of dominant plant species, dramatic population fluctuations of important insects and mammals, and a generally sparse human population. The boreal forest is also a land poised for change. During the last third of the twentieth century, many areas of the boreal forest, such as western North America and northern Eurasia, warmed more rapidly than any other region on Earth (Serreze et al. 2000). This pattern of warming is consistent with projections of general circulation models. These models project that human-induced increases in greenhouse gases, such as carbon dioxide, will cause the global climate to warm and that the warming will occur most rapidly at high latitudes (Ramaswamy et al. 2001). If we accept the projections of these models, the climate of many parts of the boreal forest will likely continue to warm even more rapidly than it has in the past. The ecological characteristics of the boreal forest render it vulnerable to warming and other global changes. Because the boreal forest is the coldest forested biome on Earth, organisms are adapted to low temperatures, and many of its physical and biological processes are molded by low temperature. Permafrost (permanently frozen ground) is widespread and governs the soil temperature and moisture regime of a large proportion of the boreal forest. Yet permafrost temperatures are close to the freezing point throughout much of interior Alaska (Osterkamp and Romanovsky 1999), so only a slight warming of soils could greatly reduce the extent of permafrost. Low temperature and anaerobic soil conditions associated with permafrost-impeded drainage constrain decomposition rate, leading to thick layers of soil organic matter. Consequently, boreal soils account for about a third of the readily decomposable soil organic matter on Earth (McGuire et al. 1995). This represents a quantity of carbon similar to that in the atmosphere. Fire is another process that could rapidly return this undecomposed carbon from the organic layers of the soil to the atmosphere.