Book contents
- Frontmatter
- Contents
- Map
- Preface
- Acknowledgements
- Map of main localities mentioned
- Abbreviations and units
- 1 An Australian perspective
- 2 The Earth: A geology primer
- 3 Building the core of Precambrian rocks
- 4 Warm times: Tropical corals and arid lands
- 5 Icehouse: Carboniferous and Permian glaciation
- 6 Mesozoic warming: The great inland plains and seas
- 7 Birth of modern Australia: Flowering plants, mammals and deserts
- 8 The history and evolution of life on Earth
- 9 Eastern highlands and volcanoes barely extinct
- 10 Building the continental shelf and coastlines
- 11 Great Barrier Reef
- 12 Planets, moons, meteorites and impact craters
- 13 A geological perspective on climate change
- 14 Cycles in a continental journey
- Sources and references
- Figure sources
- Index
3 - Building the core of Precambrian rocks
Published online by Cambridge University Press: 05 August 2013
- Frontmatter
- Contents
- Map
- Preface
- Acknowledgements
- Map of main localities mentioned
- Abbreviations and units
- 1 An Australian perspective
- 2 The Earth: A geology primer
- 3 Building the core of Precambrian rocks
- 4 Warm times: Tropical corals and arid lands
- 5 Icehouse: Carboniferous and Permian glaciation
- 6 Mesozoic warming: The great inland plains and seas
- 7 Birth of modern Australia: Flowering plants, mammals and deserts
- 8 The history and evolution of life on Earth
- 9 Eastern highlands and volcanoes barely extinct
- 10 Building the continental shelf and coastlines
- 11 Great Barrier Reef
- 12 Planets, moons, meteorites and impact craters
- 13 A geological perspective on climate change
- 14 Cycles in a continental journey
- Sources and references
- Figure sources
- Index
Summary
What do we know of the origin and age of the Earth? Was the Earth hotter or colder than now? What do we know of the origin of the Earth and of life?
The oldest rocks tell us there was a time when there were no complex life-forms. Then there was a time when life was evident, and there were the first glaciations.
Precambrian plate tectonics involved two supercontinents – Rodinia and Gondwana – of which only fragments now remain.
THE ORIGINAL EARTH
Formation of the Earth
There are some times when I wonder if we have any idea at all of how the Earth was formed. The most accepted scientific theory is that a huge, rotating shell of dust and gas, spread out across billions of kilometres of space, was left behind after the contraction of the matter that formed the Sun. This shell gradually collapsed due to gravity, the dust coalescing into a series of variously sized lumps, or planetismals. The planetismals, which ranged in size from a few metres to Mars–sized objects, then accreted by gravity over a period estimated to have been 29–100 million years. They formed spinning balls of rock, gas and ice – the planets – and Earth is one of them.
The early Earth and other planetismals were bombarded with meteorites and comets, probably the debris left from formation of the Solar System. The craters formed are visible on our Moon through binoculars.
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- Information
- The Geology of Australia , pp. 63 - 88Publisher: Cambridge University PressPrint publication year: 2009