Earth Sciences 1022A/B Lecture Notes - Lecture 8: Metamorphic Rock, Unconformity, Nonconformist
20 Oct 2016
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Superposition: each bed is older than the one above, and younger than the one below. Cross-cutting relations: sediment is usually deposited horizontally, a fault is younger than the rock it cuts, a rock is younger than the rock is cuts, inclusions are older than the rock containing them. Angular unconformity: between flat and tilted, eroded beds. Nonconformity: between parallel beds, between flat beds on eroded igneous, metamorphic rock. Dating with radioactivity: organisms evolved along distinct pathways through geologic time, left. Radioactive isotopes (parents) decay to daughters over time. Time it takes to decay to half the amount of parent left is the half-life of the isotope. Compare parent left with half-life, gives time since rock formed. In organisms c14 decays to n14 with half-life of 5730 years but is replaced by. In fossils c14 decays but is not replaced; use c14/12 ratio and half-life to get time since death.
