GEOL107 Lecture Notes - Lecture 19: Continental Crust, Oceanic Crust, Outer Core
9 Nov 2018
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Document Summary
Mostly iron and nickel with some silica. We know that outer core is liquid based on modeling of seismic waves. At angular distances of greater than 104 degrees, no s-waves arrive and between angular distances of 104 degrees to 140 degrees, no p-waves arrive at seismograph stations. Regions of no arrivals of s-waves and p-waves are known as shadow zones. S-wave shadow zone is created because s-waves don"t travel through liquids (therefore outer core must be liquid) P-wave shadow zone is created because p-waves slow down (longer travel path) when they travel through liquids (therefore outer core must be liquid) Can be defined as working model based on two fundamental principles: Outer shell of earth is divided into series of 12 or so individual lithospheric plates. These plates are in motion with respect to one another (relative motion) and with respect to underlying lower mantle (absolute motion) Plates move at velocities of 2-16 cm/yr as fast as your fingernails grow.
