Geography 2133A/B Lecture Notes - Lecture 9: Atomic Mass, Paleoclimatology, Uniformitarianism
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February 9th Lecture
Varves dierent 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
Were all full on N14+C14
C14 = most important dating piece (200-40,000 years ago)
Calibration, Veri6cation and Regression… tree rings widthstemperatures,
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
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.