18-Earth_History - Origin of the Lithosphere, Hydrosphere,...

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Origin of the Lithosphere, and a quick tour through 4.6 billion years of Earth history !
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True color image of faint blue galaxies More information at the NASA website Credits: Rogier Windhorst and Simon Driver (Arizona State University), Bill Keel (University of Alabama), and NASA. Image of the rich galaxy cluster, Abell 2218. Image of the spiral galaxy NGC 4414 More information at the NASA website Credits: Hubble Heritage Team (AURA/STScI/NASA)
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Edit of black point for Hubble Ultra Deep Field FPC
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Earth History rapid degassing (volcanism) high heat flow (radiogenic decay) intense meteorite bombardment 4600 Ma 4000 Ma Archean Eon 2500 Ma 543 Ma 800 Ma 1700 Ma 245 Ma 65 Ma Phanero- zoic Paleozoic Mesozoic Cenozoic EON ERA Proterozoic Eon 3500 Ma Ma = mega-annums millions of years before present Age of the Solar System Oldest known rocks on Earth Oldest fossils (prokaryotic cells) Mass extinctions ("end-Cretaceous") Mass extinctions ("end-Permian") fish - land plants - amphibians - reptiles dinosaurs - mammals - birds - flowering plants mammals - grasses - humans AGE 2100 Ma 1200 Ma Oldest known eukaryotic cells Oldest known multicellular organisms Widespread shelly fossils ("Cambrian explosion") Hadean (no preserved rock record on Earth) Major changes in Earth's atmosphere drawdown of CO 2 slow buildup of O 2 establishment of ozone layer formation of ocean as surface cooled 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 billions of years before present Ediacaran soft-bodied biota banded iron formations widespread stromatolites growth of continents red beds Geochemical evidence for life Early atmosphere rich in CO 2 and nitrogen (no free O 2 ) greenstone belts Hadean Eon ~4.6-4.0 Ga (giga annums = billion years
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Hadean Eon • little or no rock record preserved • continual and rapid recycling (subduction) of earliest crust due to radiogenic decay and high heat flow (much higher geothermal gradient) •e x t e n s i v e volcanism and outgassing •i n t e n s e meteorite bombardment • establishment of the magnetic field (shields Earth from the solar wind and deadly radiation) •f i r s t atmosphere , ocean(?)
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Oldest Rocks on Earth vs. Age of the Solar System • Age of meteorites and oldest moon rocks: ~4.6 Ga • Age of oldest rocks on Earth: 3.96 4.28 Ga (zircon grains in an Australian sandstone: 4.1-4.4 Ga ; this suggests the presence of crust very soon after Earth formed)
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Early Crust • Probably thin crust of mafic (basalt) or ultramafic (komatiite) composition • Readily recycled (thin and dense) • Little crust of felsic (granite) composition
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early atmosphere were likely the same/similar to those still discharged from volcanoes: Water vapor (H 2 O) Hydrogen Chloride (HCl) Carbon Monoxide (CO) Carbon Dioxide (CO 2 ) Methane (CH 4 ) Nitrogen (N 2 ) Ammonia (NH 4 ) Hydrogen Sulfide (H 2 S) Notice what’s here, …. and what’s not! * * * * The
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18-Earth_History - Origin of the Lithosphere, Hydrosphere,...

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