GEOL 1 Lecture Notes - Lecture 13: Dendrochronology, Fossil Fuel, Uranium-238
21 Sep 2020
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Galapagos islands the spot discovered (1100 km in depth) Dark/light alternating bands represent deposits during seasons (dark= colder, organic = rich, light = warmer) 1 dark layer + 1 light layer = 1 year. Need body of water to have a biologic activity at bottom. Little critters mess up recording by digging. Dark = when it stopped growing in winter. Take several samples, overlap, extend further back. Not every type of free forms (1 ring/year) Use of radioactive materials for dating specimens. Atoms of same element with different neutrons. Breakdown of an atom to achieve stability. Sequence from parent to stable daughter (some are one step, others are longer) No way to tell when atom will decay. The time it takes parent atoms to break down. Each radioactive isotope has its own half-life. Half-life does not vary with any environmental factor! Need measurable amounts of both parent and specimen daughter in your specimen.
