EES 1030 1st Edition Lecture 12Plate Tectonics Alfred Lothar Wegner- 1915 came up with the theory of continental drif that says large scale horizontal movements of continents across earth’s surface. Evidence:- Computer best fit model using continental slope rather than the coast. - Land dwelling reptiles and plants that are on different continents but of the same species. - Evidence for ice sheets at 300 Ma- Close match of rock types and structures between the continentsObjections:- No evidence for the movement of continents Paleomagnetism - the study of the record of the Earth's magnetic field in rocks, sediment, orarcheological materialsPolar wandering – apparent calculated location of north pole different for north America and Eurasia using current continent locations. Pole path trajectories match when North Americaand Eurasia are pushed back together- 1950’s and 1960’s saw first concerted effort to investigate geology of the earth’s ocean.- Earth’s magnetic field reverses periodicallyLithosphere – outer rigid shell of the earth - Divided into a series of rigid platesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Plates are in motion relative to each other and continually changing in shape and size. Asthenosphere – weak, ductile mantle beneath lithosphere- There are seven major plates and several smaller ones.- Interactions among individual plates occur along their boundaries where most of the geological action is.Three types of boundaries:- Divergent- Convergent- transform fault Divergent plate boundaries – where two plates are moving apart, magma comes up to create new crustContinental drif – continental crust splits apart at rif. Convergent plate boundary – two plates are moving toward each other and one slides under the other – subduction zone- Oceanic lithosphere cools and contracts with increasing age - denser than asthenosphereOceanic-continental convergence – continental lithosphere is denser than oceanic lithosphereContinental-continental convergence – continental lithosphere too dense to subduct. Collision zone -> mountainTransform fault boundaries – plates slide past each other. No new lithosphere is created or destroyed- Most transform faults join two segments of a mid-ocean ridge along breaks in the oceanic crust knowns as fracture zones- Plate tectonics explains global distribution of fossils- Plate tectonics is response to convection of the earthSlab pull – portion of dense lithospheric slab that can be accounted for by its subductionHot spot - volcanic regions thought to be fed by underlying mantle that is substantially hotter than other parts of the mantleMantle plumes – a localized column of hot magma rising by convection in the mantleMeasuring plate motions- ocean floor magnetic anomalies and the magnetic time scale: age of oceanic crust and spreading rate.Thermal convective flows in the upper mantle cause plates to