No other book comes even close to proposing that there is a huge mass of life living within the earth, that it is sustained in its sunless and airless subterranean environment by hydrocarbons, and that those hydrocarbons--natural gas and petroleum--are not fossil fuels but a primordial basic component of our planet and the universe.

1 Our Garden of Eden.- The Narrow Window for Surface Life.- Chemical Energy for Subsurface Life.- A Preview of This Book.- 2 Life at the Borders.- Energy Deep in the Earth.- The Ecology of Deep-Ocean Vent Life.- Other Borderland Ecologies.- Deep Is Desirable.- Beneath the Borderlands.- 3 The Deep-Earth Gas Theory.- The Origin of Petroleum: Two Conflicting Theories.- Five Assumptions Underlying the Deep-Earth Gas Theory.- 4 Evidence for Deep-Earth Gas.- Petroleum Reservoirs That Refill.- Clues in the Carbonate Record.- The Association of Helium with Hydrocarbons.- 5 Resolving the Petroleum Paradox.- The Deep Hot Biosphere Solution.- Biological Molecules in Non-Biological Petroleum.- The Upwelling Theory of Coal Formation.- Evidence for the Upwelling Theory.- An Exemption for Peat.- 6 The Siljan Experiment.- Drilling in Swedish Granite.- Magnetite and Microbial Geology.- 7 Extending the Theory.- The Origin of Diamonds.- A New Explanation for Concentrated Metal Deposits.- 8 Rethinking Earthquakes.- Mud Volcanoes.- A Challenge to Earthquake Theory.- Eyewitness Accounts.- Earthquake Spots and Earth Mounds.- Upwelling Deep Gas as the Cause of Earthquakes.- 9 The Origin of Life.- The Habitability of Surface and Subsurface Realms.- The Enhanced Probability for Life's Origin.- Darwin's Dilemma.- 10 What Next?.- Microbial Investigations.- Prospects for Extraterrestrial Surface Life.- Deepening the Search for Extraterrestrial Life.- Independent Beginnings or Panspermia?.- Afterword to the Paperback Edition.- Notes.- Acknowledgments.