GEOL-1021EL Lecture Notes - Lecture 2: Plate Tectonics, Oceanic Crust, Mid-Ocean Ridge
16 Jun 2018
School
Department
Course
Professor
GEO-1021
September 18th, 2017
October 16th, 2017
Plate Tectonics
•Plate tectonics: a theory explaining the structure of the earth's crust and many associated
phenomena as resulting from the interaction of rigid lithospheric plates that move slowly over
the underlying mantle.
•Plate tectonics is an example of scientific method:
•iterative process: every new set of observations (oceanic ridges, seismic activity etc) helps
refine the explanations
•multiple lines of evidence provide independent support
•conceptual framework of plate tectonics predicts locations of earthquakes, volcanic
eruptions and help explain past geological record
•The geodynamo Interaction with the oceanic crust
•Relative motion of inner core against outer core generates a magnetic filed which shields
earth
•certain magnetic rocks keep a record of orientation of magnetic field (some minerals are
magnetic and align w prevalent magnetic field during cooling of magma)
•Sampling of oceanic floor has shown that the magnetic field of the earth flips every few
thousand years although here are no clear explanations for this
•These magnetic reversals combined with the age dating of the rocks are the fundamental
evidence that the oceanic floor expands continuously
•Key aspects so far:
•Relative motion of plates can be tracked via GPS
•oceanic floor can be dated directly
•Distance from nearest oceanic ridge indicates relative age
•seismic data, experiments at high P and T, deep rocks carried by volcanoes provide
indirect information… please
•Age of oceanic floor: 3.8 billion years (? sources plz)
•Planet: 4.5 billion years old
•google some shit about relative rates of plate motion (: or look on the slide on D2L
