Geography 2133A/B Lecture Notes - Lecture 9: Atomic Mass, Paleoclimatology, Uniformitarianism

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February 9th Lecture
Varves  dierent layers based on seasonal changes, chemical and physical
changes (light vs dark layers….)
How do we know the age ? It is recorded (monitoring, historical data), We can
determine it using incremental or radiometric techniques
Incremental dating (varves, tree rings)…
Radioactive dating (isotopes  knowing the decay period, we can tell how old it is)
Atomic mass = #protons+#neutrons
Nitrogen 14  becomes C 14 when bombarded w. energy…
When we die, we no longer exchange carbon w/ the atmosphere, so when die this
decays…
Were all full on N14+C14
C14 = most important dating piece (200-40,000 years ago)
Calibration, Veri6cation and Regression… tree rings widthstemperatures,
precipitation.
Principle of Uniformitarianism… relationships we have today, existed in the past.
This underlies all of the research being done here with paleoclimate.
Site selection very important…
A.E douglass , was an astronomer, father of dendrochronology – study of tree
rings…
Cross dating of tree rings, using old wood in buildings, to dead trees, to living tress,
to get a timeline of precip along long period of time.
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