Planet Earth Week 2
Planet Earth Week 2 Geol 105
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This 6 page Class Notes was uploaded by Abi Sommers on Wednesday September 7, 2016. The Class Notes belongs to Geol 105 at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by John Platt in Fall 2016. Since its upload, it has received 15 views.
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Date Created: 09/07/16
8/29 (Monday Week 2) Syllabus Material Covered The Earth as a System: Earth’s core made of iron, partly liquid partly solid, generates magnetic field ( Geo Dynamo) Sun produces solar wind, made up of charged particles ( protons and electrons), creates electric current which generates magnetic fields Solar winds come from wind, go into magnetic field, field lines bend around and follow direction of solar wind Magnetosheath: Deflects solar wind Charged particles from solar wind on solar atmosphere Impact of solar wind on uper atmosphere has potential to destroy atmosphere which protects from solar radiation * Without magnetic field and solar wind, would be constantly bombarded by solar radiation Core generating magnetic field allows for life on earth Life sequestors carbon, keeping Earth’s surface cool Greenhouse effect, Co2 in atmosphere helps keep heat in and is contributing to global warming * Without life, Earth would be like, Venus, with poisonous atmosphere, no oceans or liquid water or plate tectonic, no magnetic field ( maybe because no plate tectonics) Climate System involves interactions among atmosphere hydrosphere, cryosphere (icey layer), biosphere, and lithosphere System receives heat and matter from space, energy from the sun and material falling into the Earth ( Called an Open System) 8/31 The Scientific Method: Based on the empirical method can understand the world by developing scientific explanations for observations Scientific explanations considered valid only if account for observations What we observe has physical explanation, even if beyond present understanding ● We assume basic physical laws are the same at all places and times Hypothesis: Tentative explanation of observations and experiments Theory: Set of linked hypotheses that survived repeated challenges and accumulated a substantial body of observational support Scientific Model: Predictive description of some aspect of nature based on hypotheses and established theories ● Science advances by continued testing and challenging of ideas against observations and measurements Scientific Method Continued: No explanation is closed to question Theories can never be proved A hypothesis theory, or model is confirmed by repeated observations and experiments gain credibility Longer a theory holds up to all scientific more confidently it is held One of most important tests of scientific explanation is to compare its predictions with observations Earth ’ s crust varies in thickness and density Curst is a compositional layer lying above the mantle Oceanic crust is thin and dense Continental crust is thick and has lower density Isostasy : The Floatation Principle ( example of a theory0 Crust “ floats” on underlying denser mantle Topography controlled by thickness and density of crust The Floatation Principle : A floating object displaces its own mass of fluid. If fluid has higher density than object, volume of displaced fluid is less than volume of object. So part of object stands above surface of the fluid (freeboard) This means thicker block of same material will stand higher than thinner block. Thick crust stands higher than thin crust For same reasons, block of denser material stands lower than block of less dense material, it has to displace a larger volume of fluid ● “ The Present is the key to the past” 9/2 LAB ISOSTASY : balance between gravitational forces pulling down earth’s crust. ; the equilibrium that exists between parts of the earth's crust, which behaves as if it consists of blocks floating on the underlying mantle, rising if material (such as an ice cap) is removed and sinking if material is deposited. Crustal substance Gravitational Force Crustal rebound Buoyancy force Pressure from glacial ice causes crustal subsidence, melting of ice causes crustal rebound Airy: Mountains are higher because they are thicker ( have big root like an iceberg) Volume (thickness of crust) is variable density is constant Pratt : Mountains are higher because they are less dense than other crust (float higher on mantle) Density of crust is variable Volume (thickness of crust) is constant Airy isostasy: all crust has same density, high mountains occur where crust is thickest Blocks of crust have same density Blocks of crust have different thickness Continental blocks either higher than ocean blocks because thicker than ocean blocks 9/2 Lecture Most rocks are aggregates, made up of grains Granite is a rock made up of several dif. Types of mineral grains *Rock is a complex material made of many different grains Minerals are much simpler ● Individual grains often have a simple chemical composition, and crustal structure composed of a mineral Example : Quartz is a mineral, a sand grain usually crystalline SiO 2’ Minerals Naturally occurring substance Solid Fixed chemical composition A particular crystalline structure ( Olivine: Mg2SiO 4 main constitute of Earth’s upper mantle ) Minerals to know ! Gold Au Diamond C Graphite C Halite NaCl Queartz SiO 2 Calcite CaCO 3 Magnetite Fe 3O4 Mica silicate mineral Feldspar silicate mineral (KAlS3O 8) Olivine silicate mineral Crystal Structure All minerals have crystalline structure Controls shape, appearance, and physical properties of the mineral Atomic Bonding in Crystals: Ionic Bonding There are cells in which electrons are located and electrically charged Electrons spin, get together with opposite polar “ spins” Salt is soluable, lots of ionic materials have easily breakable bonds and low densities * Exchanging of electrons Atoms not forced to be next to each other, can float of Covalent Bonding Each carbon atom linked to four others Atoms linked together by covalent bonding where they share electrons instead of exchanging them Atoms forced to stay close to one another, therefore tends to be stronger than ionic bonding Covalent bonding in carbon leads to creation of diamonds Polymorphs: Graphite and diamond are polymorphs of carbon ; have same composition but dif. Crustal structure * Crystal structure is critical in defining the mineral Graphite: So soft because covalent bonding in sheets of cells Sheets of carbon atoms have properties like metals so atoms can migrate through, and is electrical conductor Silicate Minerals silicate linked to 4 oxygens, oxygens then bond to other oxygens Tetrahedron; Si and O atoms are covalently bonded Silicate minerals make up most of planet Silicates constructed of SiO4 tetrahedra The tetrahedra may be linked into chains, sheets or frameworks. Metal ions maintain charge balance Bonding in Quartz: Silica tetrahedra linked covalently in framework, sharing oxugen atoms, formula for quarts SiO2 ● Mica is silicate ○ Has silicate and oxygen, aluminum and potassium ○ Sheet structure : silicate layer, aluminum hydroxide layer, aluminum atom, silicate layer , potassium ions Properties of Minerals: ( will learn more in lecture) color, streak, hardness, crystal shape and symmetry, cleavage, density Color may be misleading: many minerals are colored by trace impurities Sapphire and ruby are both corundum ( Al2O3) ● Garnet : prof’s fave mineral, cubic symmetry, silicate mineral
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