There is much confusion attached to the term "carbon cycle." It has been applied to different time scales ranging from hours in biological systems, to decades in future global warming, to millennia and hundreds of millennia in climate history. Much neglected is the cycling of carbon over longer time scales, and the purpose of this book is to alleviate this situation. What I call the "long-term carbon cycle" involves the exchange of carbon between rocks and the various reservoirs near the earth's surface, the latter including the atmosphere, hydrosphere, biosphere, and soils. Exchange with the surface involves such processes as chemical weathering of silicate minerals, burial of organic matter in sediments, and volcanic degassing of CO2. I have spent much time worrying about such processes and feel that it is time to show how the long-term cycle works and how to use it in deducing factors affecting the evolution of atmospheric CO2 and O2 over the past 550 million years (Phanerozoic time). This is a new world to most people studying the "carbon cycle," especially as it relates to future global warming. It is not generally realized that global warming due to the burning of fossil fuels is simply a large acceleration of one of the major processes of the long-term carbon cycle, the oxidative weathering of sedimentary organic matter.

Descriptive discussion of the long-term carbon cycle is not enough. The other role of this book is to show how one can make quantitative estimates of rates of carbon flux between rocks and the earth's surface and how these fluxes can be used to estimate past levels of atmospheric CO 2 and O2. In this way, I introduce the reader to a much needed multidisciplinary quantitative approach to earth history, which is sometimes referred to as "earth system science." I, and other workers, have published a number of papers on modeling of the long-term cycle, but there is no central place one can go to get the fundamentals of this cycle. This book is hopefully that place.

I am indebted to the many discussions of the long-term cycle with earth scientists, which are too numerous to list here. However, discussions with Klaus Wallmann, David Beerling, Dana Royer, Tom Crowley, Steve Petsch, Derrill Kerrick, Ken Caldeira, Leo Hickey, Dick Holland, Bill Hay, Fred Mackenzie, Bette Otto-Bliesner, Betty Berner, John Hedges, John Hayes, Lee Kump, and Tony Lasaga at various times over the past 20 years have been unusually helpful. Several of these people will recognize their contribution to the GEOCARB modeling discussed in this book. Special acknowledgment goes to the late Bob Garrels, who introduced me to geochemical cycle modeling in general. Without his influence this book would never have been written. Also, the book would probably not have been written now if editor Cliff Mills, at the suggestion of Brian Skinner, hadn't suggested doing so.

Organic Gardening

Organic Gardening

Gardening is also a great way to provide healthy food for you and your loved ones. When you buy produce from the store, it just isnt the same as presenting a salad to your family that came exclusively from your garden worked by your own two hands.

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