EAS105 Lecture Notes - Lecture 7: Synchronicity, Red Beds, Uraninite
7 Mar 2018
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Chapter 19, p. 470-499 the changing earth 7e. It"s time to learn the geologic time scale!! (figs. 1. 18, 17. 1; see also pdf version on eclass) *hadean correct spelling: archean eon the precambrian (pc) runs from 4. 56 to . 542 ga (billion years ago; = 542. Ma), representing 90% of earth"s history, and of that, fully 1/2 is the. Correlation in the archean is done using: radiometric dating, not fossils. Our knowledge of 90% of earth"s time is based on: <20% of the exposed rocks. Based on our understanding that the components of the solar system have a common origin, as explained in the solar nebular hypothesis [eas. Condensation of h2o produced the seas, at least by 3. 8 ga (oldest aquatic sedimentary rocks; geochemical signatures of acasta gneiss complex, and jack hills zircons [next section] argue for a hydrosphere well before. Early crust would have been of a certain type: thin and mafic (mg + fe), like oceanic crust.
