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From Fossils To Space Geology #1 What Do We Know? Solar Nebula Theory The Solar System The Primordial Earth The Primordial Earth The Solar Nebula Theory 5,000 Ma 4,600 Ma Fusion 4,500 MaMars-sized impactor Present Central disk: Sun (98.8%) Hadean Earth accretion and differentiation Hadean Earth Solid inner & liquid outer core generate magnetic field deflect solar wind Formation of Moon followed differentiation. Hadean Earth Solid inner & liquid outer core generate magnetic field deflect solar wind Formation of Moon followed differentiation. Hadean Earth Composition & Timing Hadean Earth Meteorites—leftovers Ordinary chondrites 4,600 Ma Carbonaceous chondrites (5% organics) Iron (nickel) meteorites Stony-iron meteorites Planet density decreases with distance--solar wind Earth to Sun90,000,000 miles (150 mill Km) Earth to Moon225,000 miles (380,000 Km) Earth’s position in the Solar System: Earth to Sun90,000,000 miles (150 mill Km) Extremely important: further awayice closer insteam Hadean Atmosphereoutgassing CO2 (carbon dioxide), H2O (water vapor), CO (carbon monoxide), H2 (hydrogen gas), HCl (hydrogen chloride), N2 (nitrogen gas), CH4 (methane), NH3 (ammonia), CH2O formaldehyde), HCN (cyanide) Hadean AtmosphereWhat’s missing? Oxygen generated by: 1. photochemical dissociation 2. photosynthesis Oxygen RevolutionArchean Evidence: 1. Banded iron formations ocean sediments start ~3,000 Ma: end ~1,800 Ma –UV radiation, purple bacteria, cyanobacteria Oxygen RevolutionArchean Evidence: 1. Banded iron formations ocean sediments start ~3,000 Ma: end ~1,800 Ma –UV radiation, purple bacteria, cyanobacteria Oxygen RevolutionProterozoic Evidence: 1. Banded iron formations 2. Terrestrial red beds red rocks on land start ~2,300 Ma continues today Oxygen RevolutionProterozoic Evidence: 1. Banded iron formations 2. Terrestrial red beds red rocks on land 3. Unstable minerals Uraninite not present since 2,300 Ma Oxygen RevolutionProterozoic Evidence: 1. Banded iron formations 2. Terrestrial red beds red rocks on land 3. Unstable minerals Uraninite 4. Marine copper depositsonly with oxygen began ~1,700 Ma Oxygen RevolutionProterozoic Evidence: 1. Banded iron formations 2. Terrestrial red beds red rocks on land 3. Unstable minerals Uraninite 4. Marine copper depositsonly with oxygen 5. Presence of limestones Proterozoic ocean (2,000 Ma) carbon dioxide rich no carbonates Oxygen RevolutionPhanerozoic Evidence: 1. Banded iron formations 2. Terrestrial red beds 3. Unstable minerals 4. Marine copper deposits 5. Presence of limestones Free oxygen leads to ozoneUV protection Hadean Hydrosphere Hydrologic cycle: Water sweated from interior & condensed as rain Oceans estimated at 4.2 BYA, Australian zircons Ancient crust 4,000 Ma marks beginning of Archean Anatomy of a Tectonic Plate Anatomy of a Tectonic Plate Formation of Archean Continental Crust Granulites: strongly metamorphosed and deformed— tonalite10% quartz Strongly metamorphosed volcanics and sedimentary rocks Formation of Archean Continental Crust Greenstones: Strongly metamorphosed volcanics and sedimentary rocks Granulites: strongly metamorphosed and deformed— tonalite10% quartz Formation of Archean Continental Crust Greenstones: What does the variation in composition suggestsubduction zone separation Formation of Archean Continental Crust Formation of Archean Continental Crust Time line Hadean 4,600 Ma 4,500 Ma 4,400 Ma 4,200 Ma Solar Nebula, Earth forms Moon forms Anoxic atmosphere forms Oceans start forming Archean 4,000 Ma Crustal differentiation 3,000 Ma BIF’s, atmospheric oxygen QUESTIONS?
