Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgments
- List of abbreviations
- Prologue
- 1 The planets: their formation and differentiation
- 2 A primary crust: the highland crust of the Moon
- 3 A secondary crust: the lunar maria
- 4 Mercury
- 5 Mars: early differentiation and planetary composition
- 6 Mars: crustal composition and evolution
- 7 Venus: a twin planet to Earth?
- 8 The oceanic crust of the Earth
- 9 The Hadean crust of the Earth
- 10 The Archean crust of the Earth
- 11 The Post-Archean continental crust
- 12 Composition and evolution of the continental crust
- 13 Crusts on minor bodies
- 14 Reflections: the elusive patterns of planetary crusts
- Indexes
- References
8 - The oceanic crust of the Earth
Published online by Cambridge University Press: 22 October 2009
- Frontmatter
- Contents
- Preface
- Acknowledgments
- List of abbreviations
- Prologue
- 1 The planets: their formation and differentiation
- 2 A primary crust: the highland crust of the Moon
- 3 A secondary crust: the lunar maria
- 4 Mercury
- 5 Mars: early differentiation and planetary composition
- 6 Mars: crustal composition and evolution
- 7 Venus: a twin planet to Earth?
- 8 The oceanic crust of the Earth
- 9 The Hadean crust of the Earth
- 10 The Archean crust of the Earth
- 11 The Post-Archean continental crust
- 12 Composition and evolution of the continental crust
- 13 Crusts on minor bodies
- 14 Reflections: the elusive patterns of planetary crusts
- Indexes
- References
Summary
If the great ocean were our domain, instead of the narrow limits of the land, our difficulties would be considerably lessened … an amphibious being, who should possess our faculties, would still more easily arrive at sound theoretical opinions in geology
(Charles Lyell)The next five chapters deal with the formation of crusts on the Earth. These occupy a significant fraction of this book, partly on account of their intrinsic importance to us, but also because we know so much about them. We begin by considering the oceanic crust, both because it forms a good example of a secondary crust and because the continental crust, discussed in the succeeding four chapters is effectively derived from it.
The sea floor and plate tectonics
The oceanic crust differs significantly in composition from the continental crust, a fact that has been known only for the past half-century. Before that time, the ocean floors were commonly thought to be underlain by sunken continental crust. Land bridges were invoked to explain puzzling cross-ocean similarities in fossil faunas. But in the 1950s, it was established that the oceanic crust, in great contrast to the continental crust, was both more dense and only a few kilometers thick. Thus it was most likely to be composed of dense basalt, or “sima” in the jargon of the time, that contrasted with the less dense continental granitic crust or “sial”.
- Type
- Chapter
- Information
- Planetary CrustsTheir Composition, Origin and Evolution, pp. 207 - 232Publisher: Cambridge University PressPrint publication year: 2008