Geologic Time Scale

Geologic Time Scale - Geosc 10 Thursday, April 15th, 1999...

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Geosc 10 Thursday, April 15th, 1999 Announcements: none Lecture notes: I. Geologic Time Scale (know these terms) A. Pre-Cambrian (570 million years)--these are the rocks that were present from the first explosion of multi-cellular life; these rocks occupy the vast majority of earth history prior to the beginning of abundant life forms B. Cenozoic --"Young Life" C. Mesozic --"Middle Life"; abundance of life; marks the extinction of the dinosaurs D. Paleozoic --"Old Life"; period between start of life and the events of Pangea E. Each horizontal line on the handout represents an extinction; the larger the space the larger the extinction II. All elements contain the following things A. Electrons B. Neutrons *Neutrons and protons equal the atomic mass C. Protons III. Measuring Radioactive Decay A. "Fission Track" --one atom splits apart; usually deals with Uranium; process begins by placing a rock on photo- graphic paper (Zircon and apatite are good minerals to do this with); then count the number of decays; the number
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Geologic Time Scale - Geosc 10 Thursday, April 15th, 1999...

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