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Transcript
Geologic History of the Earth (with emphasis on Manitoba) Geological History z Age of Earth: 4.5 to 4.6 Ga (4.54 Ga) z Meteorites: extra-terrestrial rocks z Moon: Apollo z Eons: z Hadean z Archean z Proterozoic z Phanerozoic 1 Hadean Eon (4.6 to 3.8 Ga) z High heat flow and development of Earth’s internal structure z Manitoba: ~3.8 near Thompson z NWT: 4.03 Ga Acasta Gneiss – felsic z Australia: 4.4 Ga – from sediments Hadean Eon (4.6 to 3.8 Ga) z High heat flow and development of Earth’s internal structure z Oldest rocks z Felsic – low density / continents (?) z Clastic sediments – hydrosphere z Celestial bodies 2 Archean Eon (3.8 to 2.5 Ga) z Development of continental nuclei and origin of life z Lithosphere: mostly 3.2 to 2.5 Archean Eon (3.8 to 2.5 Ga) z Development of continental nuclei and origin of life z Lithosphere: mostly 3.2 to 2.5 z Greenstone belts: thin slices (<20% of crust) of volcanic and sedimentary rocks crosscut by granitic intrusions z z z z Early volcanism – ultramafic flows Increasingly felsic up sequence – subaerial Deformed and metamorphosed Granite gneiss terrains: abundant – granite intrusions and metamorphic rocks 3 Archean Eon (3.8 to 2.5 Ga) z Development of continental nuclei and origin of life z z Hydrosphere: pillow basalts Atmosphere: outgassing from volcanoes – H2O & CO2 z z z Reducing CO2 rich atmosphere Need ozone (2% free oxygen) – generate remaining atmosphere Biosphere z z Origin of life: extreme environments Prokaryotes: lack nucleus and reproduce asexually; anerobic (no oxygen) Archean Eon (3.8 to 2.5 Ga) z Atmosphere: outgassing from volcanoes – H2O & CO2 z z Reducing CO2 rich atmosphere Need ozone (2% free oxygen) – generate remaining atmosphere 4 Archean Eon (3.8 to 2.5 Ga) z Biosphere z z Origin of life: extreme environments Prokaryotes: lack nucleus and reproduce asexually; anerobic (no oxygen) Proterozoic Eon (2.5 to 0.544 Ga) z Manitoba: Trans Hudson Orogen: 2.2 to 1.6 Ga – suture zone 5 Proterozoic Eon (2.5 to 0.544 Ga) Stabilization of continental platforms and oxidation of atmosphere z z Lithosphere: z z Higher abundance of sedimentary rocks than Archean, Archean, especially carbonates Continents z z z Stable: similar thickness and volume Rifting: brittle and relatively thick Similar tectonic activity as today Proterozoic Eon (2.5 to 0.544 Ga) z Stabilization of continental platforms and oxidation of atmosphere z Hydrosphere: z Well developed oceans z Atmosphere: z Oxidizing atmosphere – CO2 into carbonates 6 Proterozoic Eon (2.5 to 0.544 Ga) z Biosphere z z z z Prokaryotes Æ eukaryotes (nucleus) Single celled to multicelled Asexual to sexual reproduction By end of Proterozoic – explosion of life Phanerozoic Eon (544 Ma to present) z Modern plate tectonic period and expansion of life 7 Phanerozoic Eon z Modern plate tectonic period and expansion of life z Lithosphere: z z Sediment basins (southern Manitoba and along Hudson Bay): limestones and sandstones Volcanic ash beds from west Phanerozoic Eon (544 Ma to present) z Modern plate tectonic period and expansion of life z Hydrosphere: z z Shallow seas through much of time – cratonic sequences and epicontinental seas Glaciations from about 2 Ma to 12,000 years before present z Atmosphere: z Biosphere z z z Modern day atmosphere explosion of life: acquire hard parts Transition from marine to terrestrial 8