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Unformatted text preview: C ra9o decreases » Half‐life = 5700 years • How do we date fossil evidence? Isotopes of other elements are used for longer 9meframes – Requires igneous rocks nearby (embedded) in the sedimentary rocks » 40K/40Ar ra9o used for most events in ancient evolu9on of life » [half life =~1.25 billion yrs] – Or if no igneous rocks nearby » Paleomagne9c da9ng » ‐record of known reversals of Earth’s magne9c ﬁeld preserved in sedimentary and igneous rocks • Table 21.2 – Good summary of major eras, periods, and events in Earth’s history » D...
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This note was uploaded on 02/18/2010 for the course BIO 201 taught by Professor True during the Spring '08 term at SUNY Stony Brook.
- Spring '08