EARTH121 Study Guide - Final Guide: Unconformity, Seafloor Spreading, Mid-Ocean Ridge

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Lecture 1- Introduction to Earth Science
9 ideas of Earth Science:
- Scientific method, Water, Time, Life, System, Changes, Resources, Alter, Humans
APGO- Association of Professional Geoscientists: Protects the public by regulating geoscience in Ontario
GAC- Geological association of Canada: Promotes, discusses and disseminates geological knowledge in
Canada
GSA- Geological society of America: USA geoscience society
GSC- CANADA geoscience society
OGS- Ontario Geological survey: Provincial government geoscience agency in Ontario
What is Geology?
- Geological cycle: Sedimentation-> Burial -> Mountain Building-> Erosion
- Principle of Uniformitarianism: Processes that shaped earth throughout geologic time is the
same as today “Present is the key to the past”
- James Hutton: Theory of the Earth- Geologic time is slow, large changes requires more time
- Sir William Logan: GSC, mapping, natural resources
- J. Tuzo Wilson: Transform faults
What is a system?
- Lithosphere: rocky interior surface of earth
- Atmosphere: gaseous envelope
- Hydrosphere: water, liquid
- Biosphere: living organisms
What is earth?
- Sphere is composed of granite, basalt, peridotite, iron-nickel alloy
- Lithosphere: Crust and mantle, Make up tectonic plates, Outermost layer
- Asthenosphere: Upper mantle, Shallow under oceanic lithosphere
Earth’s layered structure
- Changes with depth
- Pressure: weight of overlying rock increases with depth
- Temperature: heat is generated in earths interior
- Earthquakes: seismic motion as a result of fault energy
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What is age?
- Relative age: order of formation
- Numerical age: actual number of years since event
Lecture 2: Plate tectonics
- Core:
outer core is liquid- magnetic field
inner core is solid- pressure
- Mantle: Solid rock
Lithosphere: solid
Asthenosphere: flow soft
- Crust: upper part of tectonic plate
Continental and oceanic
Plate tectonics Importance:
- Explains the distribution of earthquakes and volcanoes
- Origins of mountains belts and seamount chains
- Origins and age of ocean basins
Alfred Wegener’s idea
- Hypothesized a former supercontinent Pangea
- Suggested that land masses slowly drift
- Earth continually changes: continents move, split apart, and recombine
Criticism of Idea
- Couldn’t explain why continents moved
Ocean floor
- Mid ocean ranges through every ocean
- Deep ocean trenches occur near volcanic island chains
- Huge fracture zone segments the mid-ocean ridge
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- Bathymetric features include: mid ocean ridges, deep ocean trenches, volcanic islands,
seamounts, fracture zones
Harry Hess
- Seafloor spreading explains the stripes
- Upwelling magma erupts at md ocean ridges
- New crust moves away from magma
- At trenches, sea floor sinks into mantle
- Magnetic stripes near ocean’s trenches were discovered by Morley, Vine, Matthews in 1963
Rate of sea floor spreading
- Magnetic polarity reversals are imprinted in seafloor rock
- Width of magnetic anomaly stripes
Ocean Crustal Age
- Oceanic crust spreads away from ridge axis
J. Tuzo Wilson:
- Transform faults connect the ocean ridge system and divide Earth’s lithosphere into rigid plates
- Wilson’s work helped change Continental drift into the theory of plate tectonics
Plate tectonics theory
- Earths major plates:
- Lithosphere: uppermost mantle
- Strong rigid layer
- Asthenosphere: weaker region in mantle
- Explain continental drift, earthquakes and volcanoes
What drives plate motion?
- Ridge push: Elevated MOR pushes away from lithosphere
- Slab-pull: gravity pulls subducting plate downwards
Rocks: assemblage of minerals bound together
Minerals: naturally occurring, inorganic crystalline solid material with a specific chemical composition
and internal structure
Compound: substance formed by the chemical combination of two or more elements in definite
proportions and usually having properties different from those of its constituent element
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