2-27 - soil etc Age of Earth: 4.5-4.6 billion years...

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Geologic Time and Earth Cycles 17:07 Quiz 1 – Available from 2 PM today until 2 PM tomorrow Early Estimates Before 1700’s, estimates based on religious texts and ancient classical  scholars Estimates: a few thousand years Relative Ages In 1800’s, no way to determine exact ages in years Instead geologists used positions of one rock unit relative to others Absolute Age Radioactive isotopes discovered in late 1800’s Allow age of soil, rocks, and Earth to be determined Age in number of years Calculated with radioactive isotopes “Parent” isotope decays to “daughters” Occurs at known rates Ratio of parent to daughter and decay rates used to calculate age of rocks, 
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Unformatted text preview: soil etc Age of Earth: 4.5-4.6 billion years Timescales of Geologic Hazards Example: super eruptions of large volcanoes 400,000 to 700,000 years o Devastating global effects o Frequent when compared to Earths 4.6 billion years age o But in average human only ~0.011 to 0.019% chance of occurring Example: Great Earthquakes (>9.0 Magnitude) o Last for 3 7 minutes o Regional effects o ~4 per century worldwide Geological processes parts of large cycles Cycles operate over vast range of times scales o Days to billions of years Rock Cycle: Water Cycle: 17:07 17:07...
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This note was uploaded on 04/20/2008 for the course GEOL 105 taught by Professor Kohut during the Spring '08 term at University of Delaware.

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2-27 - soil etc Age of Earth: 4.5-4.6 billion years...

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