Download Exam 2 Study Guide | Planetary Habitability | EAS 1601 and more Study notes Environmental Science in PDF only on Docsity! EAS Exam 2 Study Guide Lecture 9: Segregation (chapter 7 pp 1-17) Progressive stratification of the planet, where dense materials sink to the interior and light materials rise to the surface o Fe and Ni metal core Molten outer core and solid inner core – increase in temperature, lower melting temperature of Fe metal compared to lower mantle rocks (increased with pressure because there is less room of expansion of bonds and over a range) o Upper mantle of mafic minerals olivine and pyroxenes (peridotite) Faults showing mantle reveal rock peridotite; kimberlites erupt with diamonds which show peridotite; ocean ridges form volcanic rocks by partially melting mantle which need peridotite for their composition When volume of solid is less than volume of the liquid, increased pressure and decreased temperature enhance stability of the solid Adding one substance to another lowed the melting temperature (freezing point depression) Range is bounded by inception of melting (solidus), completion of melting (liquidus) Partial melt has different composition than the bulk composition – segregation of melt to form crustal laters that differ from mantle that melted to produce them o Mafic igneous rock basalt and gabbro minerals in ocean o Quartz and feldspar (granite) in continents Oceanic and continental crust are lighter than mantle and float on top of it o Continents float at higher levels than the ocean crust Outermost layers of liquid ocean and gaseous atmosphere formed by degassing of mantle Radionuclide show that core and atmosphere formed in earliest few tens of millions of years, crust formed much later, ocean floors are geologically young because they are constantly created and destroyed o Earliest crust on earth not preserved Achondritic meteorites and study of other planes suggest that process of immiscibility, melting and degassing to produce distinct compositional layers stratified by density is common Siderophile – metal loving and in core, lithophile – rock loving and in mantle and crust (silicates), magmaphile – some lithophiles concentrated into magmas (volatiles: H2O, CO2, N2 and P, Na, K, Cl), atmophile – volatile, noble gases, occur as gas or liquid, low density, in ocean and atmosphere, chalcophile – sulfur loving and overlap with siderophile Segregation of planets from solar nebula – bulk density, low relative abundances of volatiles, preponderance of big four planet forming elements in terrestrial planets Planets not homogenous as shown by meteorites (samples from interiors of disrupted parent bodies around the solar system) Mass of earth = gR2/G F = mg F = GmMe/R2 Earth has density of 5.25 gm/cm3 Continental crust has density of 2.8 gm/cm3 and depth of 35 km Oceanic crust has density of 3.0 gm/cm3 depth of 6 km
