Download Geology 208 History of Earth System Midterm Topics 1 Topics

Geology 208 History of Earth System
Midterm Topics
Topics covered or emphasized in lecture
Uniformitarianism and science
 Fundamental assumption
 Hutton, Lyell
 Curvier and Catastrophism
Compostition of Earth:
 Four major cations and prominence of silicate minerals
Mineralogy:
 Three ways to make minerals and corresponding rock types
 Polymorphs: diamond graphite, olivine to spinel in transition zone
 Diagnostic features from structure and composition
Igneous Rocks questions can include:
 Undercooling and competition between nucleation and diffusion leading to
growth rates. Glass vs. crystalline, course vs. fine
 Implication of a phenocryst
 Hypabyssal rocks and crystal size (diabasic texture)
Sedimentary rocks:
 Diamict texture: glacial deposit (and Lahar)
 Chemical sed: BIF and LS (shallow tropical marine – Uniformitarianism)
Metamorphic Rocks:
 Definition
 Polymorphism and why the transition zone and mesosphere are metamorphic
 Tectonic setting of each type of metamorphism: Burial, hydrothermal,
thermal/contact, regional, high-pressure.
 Geothermal gradient and types of metamorphism
Structure and Composition of Earth
 Four major elements (Fe – 35%, O – 30%, Si – 15%, Mg – 10).
 How we know the composition of each layer (meteorites, geophysics and
experimental mineralogy, xenoliths).
 Moho = seismic discontinuity
 Rheologic layers:
o Lithosphere: Base of Lithosphere at 1280, flexural rigidity
o LVZ and asthenosphere: week/plastic
o Polymorph phase changes of transition zone.
o Mesosphere: Metamorphic, Perovskite, Wustite and Corundum.
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Geology 208 History of Earth System
Midterm Topics
Sedimentary Environments
 Mechanisms for raising sea level and rates of sea level rise
 Transgressive – Regressive sequences and Sloss
 Foreland basin and clastic wedge (flysch and molasse)
 Cyclothems
Relative Age
 Principles of relative age dating and block diagram
 The nature of unconformities – what is implied
 Fossil succession and extinction events
 Biostratigraphy
o Defining geologic time systems
o Problems
o Biomarkers don’t parallel formation boundaries
 Magnetostratigraphy
o DRM
o TRM – Correlate patterns on land to date reversals, construct marine
spreading histories
 Lithostratigraphy
o Define formation
o Formations are facies/environments – not same age everywhere
Absolute Age
 Uniformitarianist clocks
o Kelvin’s real problem was convection in the asthenosphere (not for Perry)
o sediment accumulation works near MOR
 Radiogenic Age Dating
o History
o Logic and the isochron
o Patterson and the Concordia
 Why did he use Pb-Pb?
 Why did he use meteorites and marine sediment
Tectonics
 Continental Drift
o History
o Problems
o Evidence favoring it – example of science: don’t toss data because
hypothesis is flawed
 Seafloor Spreading
o Hess and Dietz’s evidence
o Modern data: magnetics, heat flow, paleontology
o Oceanic crustal model (ophiolite model)
o Melting beneath a ridge
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Geology 208 History of Earth System
Midterm Topics
Tectonics continued (We will begin these on Monday. The exam covers through
Monday’s lecture)
 Subduction
o Wadati-Benioff: observation and interpretation
o Association of Trench, W-B zone and volcanoes
o Melting beneath SZ
 Transform Margins
o Tuzo’s proof
o Why do they exist – spreading on a sphere
 Wilson Cycle and Supercontinent Cycle
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