AST 2037 Lecture Notes - Outer Core, Paleoclimatology, Proterozoic
27 May 2018
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Lecture 8 – Chapter 4 (Earth habitability)
1. Eath’s iteal stutue = ie/oute oe, atle, oky ust
2. Eath’s diffeetiated layes odeed highe desity deepe i the Eath; as liuid,
olte ok ealy i Eath’s histoy
3. Sources on internal heat
a. Impact energy of accreting planetesimals
b. Friction with chemical differentiation
c. Radioactivity
4. 20% of Eath’s uet iteal heat is left over from formation, 80% is created by
radioactive decay or uranium, thorium, & potassium in core and mantle
5. Crust formed 3.7 billion yrs ago; atmosphere formed from outgassing of heated interior
6. Proof: sedimentary layers/strata deposited over time
7. 3 types of rocks = igneous, metamorphic, and sedimentary; Wilson cycle
8. Law of superposition = order of layers of rock compiled over time
9. William Smith = organized geological history into single record by using fossil in layers to
identify geological layers across different geographic regions
10. Geological time scale = know Phanerozoic, Precambrian eons (Proterozoic, Archean,
Hadean)**on test
a. Hadea = hellish, o life
b. Ahea = aiet life, sigle-celled life
c. Poteozoi = ealie life, photosynthetic & multi-cellular life (2 Gya-oxygen
buildup started boom in complexity of life)
d. Phaeozoi = isile life, really complex multi-cellular life
11. Radiometric/radioactive dating = determines age of rock through proportions of various
atom and isotope ratios with half-life unique for each decay sequence
a. Useful to determine age of specific rock layer
b. Carbon 14 works to determine age of organic matter (trees, etc.)
12. Zircons are oldest rocks that show Earth is about 4.37 Gy olds
13. Hadean Eon
a. Late Heavy Bombardment (4.5-3.8 Gya)
b. Atmosphere = main gasses emitted by volcanoes: CO2, N2, SO2; trace amounts
of O2 due to no ozone layer
c. Volatiles and water originated from comets (carboneous chondrites)
14. Alfed Wege = otietal dift led to theoy of tetoi plates
Lecture 9
15. Eath’s geogaphy: past,peset, futue
a. Plates move 2 cm/yr
b. Can project motion of conts into past/future by 108 yr
c. Continental area increases over time (MORs > subduction rate)
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