CONTENTS 



Chapter I. introduction 1 



Interest in the origin of hfe on earth 1 



Geologists and the origin of life 2 



The biological approach 4 



Religion and the origin of life 5 



About this book 5 



Acknowledgments 6 



Chapter II. uniformitarianism and actualism 7 



Philosophizing about uniformitarianism and actualism . , 7 



Catastrophism and uniformitarianism 9 



Time in geology 10 



Time through a geologist's eye 11 



Variations in intensity of processes: the pulse of the earth . 12 



Schematization in geologic writing 13 



Smaller catastrophes and uniformitarianism 14 



Uniformitarianism and its implications for the origin of life 19 



Chapter III. measuring time in geology 21 



Relative and absolute dating 21 



Relative dating 22 



Principle of superposition, 22 — Organic evolution, 23 

 ^ Eras of relative age in geology, 23 — Relative age 

 of sediments and igneous rocks, 24 



Absolute dating 25 



Physical clocks: radioactive decay series, 25 — Con- 

 stancy of radioactive decay, 26 — Pleochroitic rings, 26 



— Absolute age of igneous rocks and sediments, 29 — 

 Radioactive decay series in geology, 30 — Isotopes, 31 



— Mass spectrometry, 33 — Isotope dilution. 36 — 

 Reliability of absolute dating, 37 



The long early history- of the earth 39 



Chapter IV'. the biological approach 42 



Moscow .symposium of the International Union of 



Biochemistry 42 



