OCG 110 Lecture 5: Plate Techtonics
Document Summary
Density and pressure increase moving toward the core. Temperature increases as you go deeper and deeper to the core. Based on the total mass and volume of the earth, the average density = 5. 5g/cm^3. Rocks at the surface of the earth have a density of about 2. 8g/cm^3. Must be denser material deeper inside earth. B/c earth doesn"t wobble, it must be distributed evenly (concentric layers) Isostasy: the equilibrium of the earth crust, a condition in which the forces tending to elevate balance those tending to depress. Isostatic balance: explains the heights of the continents and the depths of the ocean basins. Balance to create equal pressure based on gravity, density, crust thickness and resulting height. Released energy is propagated away from the source as seismic waves. P (primary or compressional) wave: displacement is in the direction of wave propagation. The volume of the medium expands and contracts. S (secondary or shear) wave: displacement is perpendicular to the energy propagation.
