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
3 - A secondary crust: the lunar maria
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
One knew that the Moon had a lower specific gravity than the Earth; one knew, too, that it was sister planet to the Earth and that it was unaccountable that it should be different in composition. The inference that it was hollowed out was clear as day
(H. G. Wells)The maria
The dark lunar maria form a type example of a secondary crust, derived by partial melting from the mantle during ongoing planetary evolution. These enormous plains cover 17% (6.4 × 106 km2) of the surface of the Moon and constitute the familiar dark areas that form the features of the “Man in the Moon” and various other imaginary figures. But despite their prominent visual appearance, the maria form only a thin veneer on the highland crust (Fig. 3.1).
The lavas are mostly less than 500 meters thick, reaching thicknesses of up to 4 km only in the centers of the circular maria such as Imbrium. They cover an area that is only a little more extensive than that of the submerged Ontong Java basaltic plateau, which lies north east of the Solomon Islands in the Pacific Ocean. The total volume of the maria, about 1.8 × 107 km3, is trivial compared to the anorthositic crust or the whole Moon. This compares with the total volume of the current terrestrial oceanic crust of 1.7 × 109 km3, two orders of magnitude larger.
- Type
- Chapter
- Information
- Planetary CrustsTheir Composition, Origin and Evolution, pp. 61 - 85Publisher: Cambridge University PressPrint publication year: 2008