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Clerical:
Quizzes 1 - 4 are posted.
Exam #1 will be given during class on Wednesday (2/10/10). The Exam #1 Study Guide is posted.
Themes of the Day:
- Geologic Time (continued)
- Geologic History of the Earth
Geologic Time
Geologic History of the Earth
- Age of the Earth ~4.6 to 4.5 Ga (billion years old) - equivalent to formation of our solar system
- Oldest terrestrial mineral ~4.4 Ga (zircon, western Australia); Oldest surviving rocks on Earth ~4.0 Ga (Acasta gneiss - northern Canada)
- Outgassing and evolution of the atmosphere and oceans
- Earliest fossil evidence for life (single celled organisms) ~3.5 Ga - stromatolites (algal mounds) common throughout Precambrian
- Formation of continental cratons (shields) - Plate Tectonics operational
- Cambrian explosion (rapid diversification of multicelled organisms) ~570 Ma (million years ago)
- Geologic time scale - many subdivisions since ~500 Ma reflect a preservational bias in the geologic record
- Paleozoic Era
- Mesozoic Era
- Cenozoic Era
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