Geo 101N 1st Edition Lecture 8Outline of Last Lecture I. Plate TectonicsII. Lithospheric LayersIII. Margins continuedIV. Earthquakes and BoundariesOutline of Current Lecture V.Plate BoundariesVI. Pacific NorthwestVII. Measuring Plate MotionCurrent LectureV. Plate Boundariesa. Oceanic Lithosphere: hot asthenosphere @ the base of a ridgei. Ageing crust moves awayii. Becomes more dense as it agesiii. Beginning subduction: old oceanic lithosphere is more dense than mantleiv. Once the flat lying plate begins subducting it becomes a part of a system of convectionb. Mariana Trench-oldest known ocean crust on the earthc. Wilson Cyclei. Tuzo Wilsonii. Cyclical impacts of platetectonics on globalfeatures VI. Driving Forcesa. Ridge push: elevated mid-oceanic ridge pushes thelithosphere awayb. Slab-pull: gravity pulls asubducting plate downwardc. Convection: in theasthenosphere adds to orsubtracts from thelithosphereThese 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.VII. Convergent Boundary: Oceanic plate to oceanic platea. Where two plates…convergeb. Older, denser plate gets subducted, partially melts into magma, rises forming volcanic islandsc. Key features: trenches, volcanic arcd. Ex: Aleutian Islandse. Evidence for subduction: frequent earthquakes; eq’s occur deeper as the slabs subducts.VIII. Convergent Boundary: Continental to continentala. Subduction creates mountainsb. Subduction related volcanic arcs grow on overriding platec. Accretionary prisms (addition of sediment to a tectonic plate) grow upd. Thrust faults stack up on the far side of the orogen (develop while a continental plate is crumpled and is pushed upwards to form mountain ranges)e. Ex: Alps, Andesf. Subduction consumes ocean basinsg. Ocean closure ends in continental collision; subduction ceases; subducting plate detaches and sinks – makes the largest mountains in the worldIX. Triple junction a. Multiple junction combinationsoccureb. Point where 3 platesboundaries intersectX. Plate motion:a. Relative motion: the perceiveddifference of velocitiesbetween moving bodiesb. Absolute motion: the “actual”velocity of a given thingirrespective of motions arounditc. Measuring: plate vectors aredetermined by