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Earth Science Midterm Notes.docx

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John Mc Namara

Earth Science Midterm Notes 1a: What is geology? • Geology: Ascience that deals with the history of the earth and its life especially as recorded in rocks • Physical Geology: Involved with the processes that act to form the earth and the products of those processes (eg: Minerals, plate tectonics, earthquakes) • Historical Geology: Involved with the interpretation of the history of the earth. • Environmental interpretation of rocks + age of rocks = Earth history • Environmental interpretation: The present is key to the past; examining the characteristics of various environments on earth can interpret the environments in which ancient sediments were deposited • Age of rocks: Based on relative age (relative to associated rocks) or absolute age (radiometric dating) • Science: Is a system of knowledge that is based on general truths or facts as they are known at the time. Science is thus a methodological approach to studying the natural world. • Deductive Reasoning: To draw conclusions regarding a phenomenon based on all that is known about it. D.R examines the available information/data and comes to the most likely answer until proven wrong later. • Hypothesis: Alogically derived explanation that is based on a body of knowledge that is made up of facts • “The greatest obstacle to progress in science is the illusion of knowledge, the illusion that we know what is going on but we don’t” – Professor Mike Disney • ScientificApproach: Start with a hypothesis, identify the ways to prove that hypothesis, identify flaws in the hypothesis, test the hypothesis and null- hypothesis, confirm or disprove the hypothesis, present it as a theory. 1b: Why should be interested in geology? • The availability of mineral resources is a measure of the wealth of a society • Mineral Resources: a useable economic commodity extracted from naturally formed material (elements, compounds, minerals, or rocks) • Mineral Reserve: Is the portion of a resource that is identified and currently available to be extracted legally. The defining factors determining a reserve include: geologic, technological, economic, and legal factors. • Most elements are widely dispersed in earth’s crust. They must be concentrated by geologic processes in order to be economic • The most valuable metallic minerals: nickel, gold, copper, and iron ore • Asbestos: Greek word meaning unquenchable or inextinguishable is a set of 6 silicate minerals with long, thin fibrous crystals exploited commercially for their desirable physical properties: sound absorption, tensile strength, and resistance to heat, electrical and chemical damage. • Most precious stones (diamond, ruby, sapphire, and emerald) are rare and durable and valuable specimens are relatively large • Metallic minerals: are called ores; ores of copper, gold, zinc, silver, and mercury illustrate the characteristic metallic luster of these economic minerals. • Many ores are sulfides (eg: the led ore galena) • Acid Mine Drainage: a serious environmental impact of mining due to the heavy mental concentration in the river (Rio Tinto river) • Many ores are enriched by hydrothermal processes; where hot groundwater dissolves ions and deposits them in high concentrations elsewhere. • Adifferent type of hydrothermal process occurs at spreading centers, where hot, mineral rich water rises to the seafloor, forming black smokers • Environmental impact: occurs from mineral exploration and testing, mineral mining, mineral resources refining, and mining waste disposal. • The impact of resource exploitation depends upon factors like: mining procedures, hydrologic conditions, climate factors, types of rocks and soils, and topography. • 2 Mining Techniques: Surface mining and sub-surface mining (underground) • Surface mining: Done by removing surface material to reach buried ore deposits • Minimizing The Impact of Mining: 1. Knowledge and technology transfer: developed countries to developing countries 2. Environmental Regulations: Forbid bad mining practices, clean air act, and on- and offsite treatment of wastes 3. Land Reclamation: 50% of the land used in the mining industry reclaimed 4. New Biotechnology: Bio-oxidation, bioleaching, bio-sorption, and genetic engineering • Asbestos includes 6 different mineral fibers • Amphibole comprises 5 mineral fibers • Serpentine category comprises only one mineral fiber, called chrysotile • Chrysotile is in a different class of silicate minerals and makes up 99% of world asbestos 2: Mineralogy: The building blocks of Rocks • Chemistry is the foundation of minerals • Minerals: Naturally occurring, inorganic, formed by geological processes, solid, ordered internal molecular structure, and definite chemical composition • Rock:Asolid mass of minerals • Minerals are the basic building block of geologist. In order to build minerals, the atoms of chemical elements must join together by forming bonds. • Ununquadium: Heaviest synthesized element • 114 known elements, 90 are naturally occurring • Atoms: smallest particles of matter, retains all the characteristics of an element • Atomic structure consists of protons (positive) and neutrons (no charge) • Electrons: Negatively charged particles that surround the nucleus, lighter than a proton, located in discrete energy levels called shells • Elements: most basic forms of a chemical, they cannot be broken down by any physical or chemical process • Protons + Neutrons = Mass • NaCl is most abundant in the sea • Atomic number: The number of protons in the nucleus gives each atom its special chemical characteristics. Elements are catalogued by their atomic #. • Uranium: 92 protons, highest atomic number of the naturally occurring elements • Ions: Charged atoms • Cations: Positively charged, loss of electrons • Anions: Negatively charged ions, gained electrons • Molecules: product of the joining of 2 or more like or unlike atoms • Only 8 elements are common within geological materials (rock forming materials) • Oxygen and silicon are the most common element in the earth’s crust and mantle • Hydrogen: Lightest element, highly combustible, most major element in the sun • Helium: Light gas, unreactive • Nitrogen: Most common gas in the atmosphere (78%), essential component of amino-acids • Oxygen: Earth’s most abundant element, comprises 21% of earth’s atmosphere • Neon: Noble gas, unreactive • Sodium: Very reactive, common in the earth’s crust • Calcium: Enriched in bones, reactive metal • Aluminum: Light metal, highly reactive • Silicon: Second most abundant element • Iron: Key element of the earth’s core • Bonding: Joining of 2 atoms in a stable arrangement • Elements will gain, loose, or share electrons to attain the electron configuration of the noble gas closest to them in the periodic table • 3 kinds of bonding: 1. Ionic: result from the transfer of electrons from one element to another (a metal transfers an electron to a non-metal) 2. Covalent: result from the sharing of electrons (two non-metals combine or when a metalloid bonds to a non-metal) 3. Metallic: result from metals held together in a “sea of electrons” • Amineral consists of an ordered array of atoms chemically bonded to form a particular crystalline structure • Polymorph: some elements can join in more than one geometric arrangement (composition stays the same, physical properties differ) • Physical Properties of Minerals: 1. Crystal Habit: Shape 2. Lustre: Appearance of a mineral in reflected light, 2 basic categories: Metallic & Nonmetallic 3. Color 4. Streak: Color of a mineral in its powdered form when rubbed on an unglazed porcelain tile 5. Hardness: Resistance of a mineral to abrasion or scratching • Mohs Scale: Standard scale used to measure a minerals hardness • Physical Properties of Minerals: 1. Cleavage: tendency to break along planes of weak bonding, produces flat, shiny surfaces 2. Fracture: Absence of cleavage when a mineral is broken 3. Specific Gravity: Ratio of the weight of a mineral to the weight of an equal volume of water • Silicates: Most common rock forming mineral (eg: quartz, hornblende) • Non silicate minerals: oxides, hydroxides, sulphides, sulphate, carbonates, native elements, halides, phosphate 3: Igneous Rocks • Igneous Rocks: Formed from molten rocks that solidifies • Partial melting: • Magma is below the surface and Lava is above the surface • Igneou
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