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Age of the Earth?
Formed about 4.6 billion years ago
Radioactivity produced by?
Decay over time
For organic materials, contains carbon and comes from a living thing. Can be used up to 75,000 years ago
Carbon 14 Dating Isotopes
Found in all living things. Determined by ration between Carbon 14 and Carbon 12
88% of Earth's history
Gases in original atmosphere
Carbon diaoxide, water vapor, nitrogen, but NO oxygen
Precambrian rocks contains fossils of one-celled organisms, resembling modern “cyanobacteria,” using H2O, CO2 and energy to make oxygen [photosynthesis] these “prokaryotes” had NO nucelus
First period of Paleozoic
Ordovican Period events
- land plants appeared and vertebrates became more common
- Vertebrates appeared as jawless fishes
Mesozoic life extinction
- Dinosaurs and most large
- animals disappeared 65 million years ago b’cause Meteorites impact the Earth
- Evidence? A worldwide layer of sediment,
- containing element Iridium—rare in Earth, but found in meteorites, Volcanic eruptions, Disease
Mammals, mammoths, sloths, sabre-tooth cats, wolves, bison, and homosapiens
Quaternary Period, about 10,000 years ago