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by: Kassandra Ortega

Geologylecturenotes.pdf Geology 101

Kassandra Ortega

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Lecture notes filled in from Wilkies Class.
Geology 101
Class Notes
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This 118 page Class Notes was uploaded by Kassandra Ortega on Tuesday November 3, 2015. The Class Notes belongs to Geology 101 at Washington State University taught by Wilkie in Fall 2015. Since its upload, it has received 31 views. For similar materials see Geology 101 in Environmental Science at Washington State University.

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Date Created: 11/03/15
Lecture Outline Monday September 8 – Monday September 15 Key Points for today • What is a mineral? • What causes atoms to combine to form minerals? • What conditions are necessary for minerals to form? • What are some of the physical properties that we can test for to help identify/name a mineral? What is a Mineral? • ______________________________________________________________________________ • _____________________________________________ _________________________________ • crystalline solid - atoms are arranged in a _____________________________ (ex: a cube) • Specific chemical compound - contains particular elements in a set ratio. – H O has a set ratio. Is it a m ineral? What about mineral water? Ice? 2 – FeS 2yrite (fools gold) Atoms • Composed of a nucleus – Protons (+) – Neutrons (no charge) • Electrons (- charge) orbit the nucleus in shells (orbitals). Atomic Number = # of ______________ in the nucleus. Ex: Carbon atom (6) Atomic Mass = # of ___________ + ____________. Ex: Carbon atom (6 protons, 6 neutrons: 12) Protons –atomic mass 1 Neutrons –atomic mass 1 Electrons –atomic mass ~ 0 Isotopes = the # of neutrons may change • All carbon atoms have 6 protons (atomic number). The atomic mass = 6 protons + 6 neutrons = 12 Ex: Carbon 13 (7 neutrons) and Carbon 14 (8 neutrons) are all isotopes of Carbon. Electrons • Electrons are attracted to __________________ and form an electron cloud around the nucleus. • For stable atoms, the number of electrons = the number of protons. • Ion, is an atom which has ___________________________________________. ex. Na + (cation) - and Cl (anion) So how does this make minerals? • Minerals form when atoms transfer or share electrons to fill there shells = chemical bonding. Chemical Bonding • Atoms combine (bond) by losing, gaining or sharing electrons to form minerals. Ionic Bonding • ______________ of electrons. • Form when shells are nearly empty or nearly full. • ______________ bond. Covalent Bonding • ______________ of Electrons • Form when shells are about half full • ______________ bond Ionic bonding Covalent bonding Carbon has 4 electrons but would like to have eight. Covalent bonding: Each atom shares electrons Every C atom “sees” 8 electrons. (fills the electron shel-- Diamond! How does this affect the physical properties of diamonds? See Table 3.4 for relationship of property to composition and crystal structure. What Mineral Will Form? (depends on) • Available Elements • Ionic Substitution • Conditions of Crystallization – Polymorphs (same composition but different crystal line structure) • Ex: Diamond and Graphite both formed carbon How do Minerals Form? Chemical reactions between elements. Crystallization – the growth of a solid from a gas or liquid whose constituents come together in the proper chemical proportions and crystalline arrangement What conditions cause minerals to form? • Lower the temperature of a liquid below its freezing point • Liquids evaporate from a solution forming a supersaturated solution and results in precipitate • When atoms and ions in a solid become mobile and rearrange themselves at high temperature (>250 °C) Mineral Identification • Different minerals look different because they have different physical properties. • This is a result of chemical composition (formula) and crystal structure. Mineral Properties Color • least reliable - do not use alone • Color depends on the presence of certain ions, such as iron, chromium, cobalt Luster • How the surface reflects light_____________________________. • Metallic vs. Non -metallic Streak • Color of a mineral in powdered state • The tendency of mineral’s to break along planes of ___________________________. • Weaknesses within the structure allow the mineral to break along specific planes. This is called cleaving. Cleavage – the tendancy of minerals to break long planes of weakneses Fracture • ____________________________________________. Hardness - • A mineral’s resistance to scratching & abrasion. • Based on Moh’s Hardness Scale (Table 3.3) Things that affect hardness 1. Atomic structure of the mineral 2. Type of chemical bonds which hold the mineral together 3. The types of atoms that form the mineral Specific Gravity (SG) • Ratio of weight to an equal volume of water. • Basically, how heavy it feels relative to other minerals. Things that affect density • Atomic weight of the atoms • Crystal structure Crystal Habit • Characteristic shape as it grows. Ex. Quartz (6 sided), Garnet (12 sided) Atomic structure also affects how the mineral grows Special Properties of Select Minerals Smell and Taste • Sulfur or Halite Fluorescence • Some minerals glow under UV rays. Magnetism • Magnetite Effervescence • Calcite reacts with HCl (acid). Double Refraction • Light is split into 2 rays = 2 images Lecture Outline Fri. - Mon. September 12 -15, 2014 Questions ?? Lecture Quiz Friday September 12, 2014 • Type of question: – Short answer – Fill in the blank – Identification of a feature from slides • Length 15-18 questions (20pts) Covers material thru Wed. Sept. 10 Key Points for today • Recognize that mineral are grouped by there crystal structure and composition • What is the controversy associated with Asbestos? • How are mineral deposits formed? • What is a mineral deposit and why is it located where it is? • What are the characteristic properties which make a mineral a gem? • Where do diamonds come from and how do the make there way there? Mineral Groups Silicates • Most abundant mineral group in the crust (clicker question) • Dominates all three rock types -4 • Composed of Silicon and Oxygen= silica tetrahedron (SiO ) unst4ble has a negative charge anion • Crystal structure Isolated, single chain, double chain, sheet, and framework • asbestos is a chain silicate Non-Silicates Carbonates, Oxides, Sulfides, Sulfates, Native Elements Why do some minerals have nice crystal form and others do not? • If the mineral grows slowly and has space it will tend to form nice crystals, • If many different minerals are growing at the same time and they are touching each other then they will grow together. Why are minerals important ? We use minerals in our everyday life. Point to think on: Name a time in man’s past where we did not rely on minerals or the materials made from minerals. How far back do we need to go in man’s past? Cavemans as long as there were tools they were using minerals Are all minerals good for us? Asbestos, What’s the deal? • Asbestos is commercial definition for minerals that are flexible, chemically and thermally resistant and can be woven. ( for federal regulation purposes) ( can be used for insulation, textile and cloth products) • Fiberous crystal form • Previously used in building products (tiles, etc.) and insulation products. • Heavy exposure to some types of asbestos has been linked to lung cancer. • Six minerals are considered to be commercial asbestos: – Chrysotile (sheet silicate from the serpentine group) + four other double chain silicates from the serpentine group – Crocidolite (double chain silicate from amphibole group) Asbestos, Do we need to spend $50,000,000,000 to $150,000,000,000 to get rid of it? Crocidolite • Forms sharp fibers (needles) that can puncture lungs and is implicatd in lung disease Chrysotile • Fibers dissolve more easily (not sharp) • Has never been shown to cause lung related diseases. • The only type of asbestos that is currently mined. • The most commonly used type of asbestos in N. America. The key point is not all forms of asbestos are lined to lung disease but the federal gov. treats them alike How do Minerals Form? Chemical reactions between elements. Crystallization – the growth of a solid from a gas or liquid Where do minerals co me from? 1. Lower the temperature of a liquid below its freezing point. Ex. Crystallization of a magma forming an igneous rock 2. Evaporites - Liquids evaporate from a solution causing minerals to precipitate • Lagoon is full of different ions and is restricted so water can not be replenished • Liquids evaporate from a solution forming a supersaturated solution and results in precipitate “NaCl” - halite crystals form • All Na is consumed. However, there are still other ions left w ith more evaporation • Saturation of KCl (sylvite) and KCL crystals form and precipitate – process continues until all water is evaporated Salt deposits are found worldwide – found on almost all continents Examples where evaporates are currently for ming: Bonneville salt flats in Utah and death valley california … great salt lake Other mineral formed by evaporation are gypsum and anhydrite: “Plaster of Paris” and is used to make sheet rock for interior walls of houses. Where do mineral come from ? 3. Hydrothermal Fluids Hydrothermal fluids are created by the circulation of water through hot rock or near a magma chamber. The water is heated and is able to dissolve elements forming a weak acid solution. The hot acid solution is able to leach and pick up small amounts of gold and other metals and elements. The hot fluids rise and as they do they can precipitate the metals (by boiling, a change of temperature, change in acidity, or change in pressure). The result is that the gold and other metals a re left behind and concentrated. Because the metals are concentrated to a sufficient level, it becomes economic for mining operations. Low grade concentration use open pit mining methods and high grade concentrations use much smaller underground tunnels for mining veins associated with faults and fractures in the rock. “Mother Lode” Au in California Au was leached from the surrounding rock by hydrothermal fluids associated with the Sierra Nevada Batholith. The gold was deposited in veins and with milli ons of years of weathering the gold was liberated by erosion and washed into streams. Gold has a density of about 19gm/cc. Gold is very heavy and as a result it sinks to the bottom of the streams in low areas and becomes concentrated (placer deposit – this is a very effective process). Placer gold was discovered in mid 1800’s at Sutters Mill starting the California gold rush. 4. Minerals formed by metamorphism: High heat and pressure allows different minerals to form while still in the solid state (nothi ng melts). Garnets and other metamorphic minerals form in this way. You can find garnets if emerald crust, Idaho. What makes a gem? • Beauty – as reflected by color and luster • Transparency • Brilliance – enhanced by cutting and polishing • Durability – based on hardness • Rarity or perceived rarity Diamonds • Covalent bonds • 10 on hardness scale • Polymorph of carbon along with graphite • Form in a zone with in the upper mantle • Most are believed to be very old (most about 3 billion years old). • Brought to the surface through kimberlite pipes. (Explosive eruption, kinda like a volcano ) • Can be found as placer deposits. (gold panning) • Uses: Gems, Cutting and Polishing Diamonds only exist on the surface because they were brought up fast, if they were allowed to equilibrate on the way to the surface the stable form of carbon would be graphite. Location of kimberlites (get from map) Are there gems more expensive than Diamond? In comparison to clear diamonds there are more expensive gems. Bixbite is a red beryl (same composition as Emerald but different color) and is very rare; maybe 1 or 2 localities in the world. One is in the Wah Wah Mountains in Utah. However, intensely colored _ diamonds such as red___ are by far the most expensive. Lecture Outline Wednesday September 17, 2014 Questions? Key Points for today • Be able to identify differences between intrusive and extrusive igneous rock textures • Understand how the rock composition affect melting and crystallization • Understand tectonically where magmas are generated and how it affects there composition Minerals to rocks • Now we can combine one or more minerals to form different rocks! Rock Appearance Based on: 1. Mineralogy (what mineral are there are they light colored or dark colored) 2. Texture – size, shape and arrangement of the minerals. (coarse, fine, layered, etc.) 3 Major Rock types: Igneouse – form by the solidification of molten rock or melt Sedimentary – form by either cementing together fragments of preexisting rocks or by precipitation of mineral crystals out of water solutions at or near the Earth’s Surface (weathering_ Metamorphic – form when preexisting rocks change character in the solid stat e as a response to a change in pressure and temperature conditions (does not require melting). (continent to continent collision) Where do we see rocks in nature? • Outcrops – rock weathers from the surface • Road cuts • Stream beds • Drilling – to see beneath • Bedrock – starts at surface goes into the earth The Rock Cycle (important - need to understand and state in own words) Now we can combine one or more minerals to form different rocks! Chapter 4 - Up from the Inferno: Magma and Igneous Rocks Igneous Rocks: Why should we care? • Igneous rocks make up the bulk of the Earth’s crust • Earth’s mantle is essentially an enormous igneous rock • Igneous rocks are economically important • Many igneous rocks form striking landscape features Types of Igneous rocks Extrusive Igneous Rocks (also called Volcanic) • Form when magma erupts at the surface (= lava). • Cools faster and rapidly are going to be smaller crystals Intrusive Igneous Rocks (also called Plutonic) • Form when magma cools underground. Does not erupt at the surface. • Cools Slower • Forms igneous bodies below the surface. Can see the crystals Igneous rock textures Intrusive (Plutonic) Igneous Textures • Cool slowly • Coarse crystals – Phaneritic (all visible) – Pegmatitic (very large) Extrusive (Volcanic) Igneous Textures • Cool rapidly • Fine or no Crystals • May form when lava or pyroclastic material erupts. • Textures – Aphantitic- crystals are too fine to be distinguished without a microscope. – Glassy - glassy no minerals present (obsidian – _Pyroclastic- Fragments of material ejected explosively into the air. - Pumice - Ash - Tuff – Vesicular- Void spaces that where gas bubbles Mixed Texture • Porphyritic – 2 distinct crystal sizes. • What does this indicate about the rate of cooling? At one point magma came in an started to cyrstalize then cmae to the surface and rapidy grew Phenocrysts (big crystals) – slow cooling Matrix (background) is aphanitic – fast cooling Composition (only need to know order relative to silica content) • The silicates (silica + other elements) are the major constituents of igneous rocks. • Igneous magmas, lavas, and rocks are categorized based on the % silica content relative to other elements. Ultramafic –lowest % silica, dark colored (green) mafic– low % silica, dark colored (green/brown/black) Intermediate– intermediate % silica, intermediate color (grey, grey/green) Felsic – high % silica light color (white, light grey, pink) Distribution of Igneous Rock Types • Ultramafic, Mafic, Intermediate and Felsic Igneous rocks are not evenly distributed around the world. • Why? – Partial Melting – Plate Tectonics Melting Rocks - How do we melt rocks? 3 ways: 1) Raise the temperature (deeper in the Earth the higher the temperature) - “heat-transfer melting” 2) __________________________ - “decompression melting” 3) Add volatiles – H2O, CO2, etc. “reflux melting”______________________ temperature The rock composition affects melting temperature (silicic or felsic -> lower temperature mafic -> higher temperature) Partial Melting • Rocks are composed of different minerals. • Minerals melt at dif ferent temperatures. • Only a fraction of a rock might melt, depending on the temperature and pressure conditions. Analogy: M&M chocolate candies on a hot summer day. Melting Temperatures (do not need to memorize only need to know relative orde r) Felsic 600-800 degrees C Intermediate 800-1000 degrees C Mafic 1000-1200 degrees C Ultramafic greater than 1200 degrees C Magma composition can be affected by other factors: magma mixing and assimilation of country rock From Magma to Igneous Rock • Magma – Cools – Solidifies (freezes) – Forms silicate minerals • Bowen’s Reaction Series - Not all minerals ______________________________________. There is a sequence based on the elements present and the mineral structure - The first minerals to melt are the last one’s to crystallize Generation of Magma Divergent boundaries Mid-Ocean Ridges • _____________ composition Basalts dominate (most of ocean floor) • Partial Melting of Upper Mantle Convergent Boundaries Continental/Oceanic Ocean Island Arcs (Ex. Andes, South America) and Continental Volcanic Arcs (Ex. Cascades) • _______________ to ______________ Composition Andesites/Diorites to Rhyolites/Granites • Partial Melting from Plate Subduction Mantle Plumes - Hot Spot Volcanic Island Chain (Ex. Hawaii) • ______________ composition Basalts dominate • Melting of the mantle Continental Caldera (Ex. Yellowstone) • ____________ to intermediate composition • Partial melting from overlying plate and mantle Important point: The composition of the magma is a reflection of where the melting took place and what type of lithosphere is involved Intrusive Igneous Rocks: types and shapes • Volcano – A hill or mountain that forms from the accumulation of lava that erupts at the surface. • Plutons – Large igneous bodies that cool underground (intrusive). The type and shape of an intrusion is based on the size, shape and emplacement orientation Batholith: The largest of intrusive igneous rocks bodies. Sill: intrudes _____________ to sedimentary bedding, many are ____________ Dike: ____________________________ intrusion which cuts across other rock types Lecture Outline Monday September 29, 2014 Questions? Key Points for today (Interlude B - A Surface Veneer: Sediments and Soils) • Understand what is meant by weathering and erosion • Why do different rocks and minerals weather at different rates? • Be familiar with examples of both physical and chemical weathering • Develop a basic understanding of how soil formation is affected by climate, time, organisms and slope steepness Weathering, Sediments and Sedimentary Rocks Why is weathering and erosion important? • Sedimentary rock makes-up about 75%of land surface • provides soil for growing food and forests • It sculpts and modifies the Earth’s surface – if is responsible for all our landscapes Weathering and Erosion Weathering is the process by which rocks are broken down at the earths surface Erosion is the process that moves pieces of rock and deposits them elsewhere – Wind – Water – Ice – Gravity What Controls Weathering? • Rock properties – Hardness, composition, solubility, zones of weakness • Climate – Wide variations in temperature and moisture accelerate weathering • Soil and vegetation – Exposes rock to variations in moisture and chemistry • Length of exposure 8 Rock Forming minerals Felsic (quartz, k feldspar, muscovite) Mafic (Biotite, amphibole, pyroxene, olivine) What conditions would cause rocks to break down faster? the higher the temperature. And solubility Slower?Mineral stability determines whether a rock is stable or decomposes Mineral stability determines whether a rock is stable or decomposes Which mineral group (felsic or mafic) is more stable? Why? FELSIC Which minerals are the least stable? Why? Calsite, Halite Which minerals are the most stable? Why? Iron Oxide Weathering • Physical –fractures rocks breaks material into smaller pieces • Chemical – converts minerals and rocks into altered solids, solutions and precipitates - only occurs to those materials exposed to the elements “weather” Weathering and Erosion generate sediments. Physical weathering: • Frost wedging – alternate freezing and thawing cycle • Roots – the roots get bigger and break material • Exfoliation, example: Yosemite national park –sheeting on half dome. Chemical weathering: Water is naturally acidic (slightly) .. onto calcite Chemical weathering processes: • Hydrolysis – the reaction of any substance with water - Gains water Ex: Feldspar -------- forms -----Clays • Oxidation – A mineral reacts with oxygen to make a different product Ex: Iron in minerals (like pyroxene) ----- Hematite (Fe2O3) What color does it turn the rock? REDis orangish – rust • Dissolution – Minerals dissolved by water or acids. Ex: Halite, Calcite By-product of weathering: Soils Soil forming factors • Climate - Temperature & precipitation: higher temperatures and more rainfall means more weathering and thinner soils • Time - Longer time = thicker soil • Plants/Animals - Organic matter • Slope - If too steep, little/no soil – increased erosion Soils and Climate • Soil formation is directly linked to climate that the soil forms in and is the product of both physical and chemical weathering Three major groups • Wet climate (thin organic zone, little organic material in A horiz on, extreme chemical weathering) • Temperate climate (thick, abundant organic material in A horizon) • Dry climate (little vegetation, very little soil formation) How do the soils change from forest to desert to rain forest? Which climate develo ps a thicker soil profile? Temperate Why? Why does a soil formed in a wet tropical climate have less organic matter in the A horizon than a soil formed in a temperate climate? The product of weathering is SEDI MENT • Mineral and rock fragments of the parent rock • Solid products of chemical alteration – clay minerals • Ions dissolved in rainwater and soil water Lecture Outline Wednesday October 1 - Friday Oct. 3, Chapter 6 – Pages of the Past: Sedimentary Rocks Key Points for today • Be able to identify the 3 categories of sedimentary rocks using texture and composition • Be able to recognize the different types of sedimentary structures • Understand how sediments are converted to sedimentary rocks Sedimentary Rocks Clastic (Detrital) Biochemical Chemical Where are the different types of sedimentary rock types found? Abundance by Sedimentary rock types Siltstone, mudstone, and shale 75% Sandstone and conglomerate 11% Carbonate rocks 14% What about chemical precipitants? ( very minor) Clastic/Detrital Sedimentary Rocks • Composed of pieces of pre-existing rocks (clastic sediment). • Classified by texture (size, shape and arrangement of sediments.) • Mudstone • Sandstone • Conglomerate or Breccia Texture is affected by transport process (Terms may be used to describe sediment or sedimentary rocks) • Particle size –clay, silt, sand, gravel (pebble, cobble, boulder) • Shape – Angular to Well Rounded – smoothing of fragment edges • Sorting (similarity in size) – Well Sorted to Poorly Sorted Sorting – are the particles about the same size? If yes – well sorted. If no – poorly sorted. How do grain size, shape and sorting change with increase in transport distance? • The more angular the less the transport. The more rounded the greater the transport. • With more transport the particles become smaller and better sorted (similar in size). The size of the particles reflects the energy it takes to move them. Example: for a stream to move large particles like cobbles and bould ers the moving water must be very fast – high energy. However if the stream is only capable of moving fine particles like silt and clay then the water in the stream must be very slow – low energy. Biochemical Sedimentary Rocks • Comprised of the remains of organisms (plants and animals). • Classified by composition. • Ex: Limestone shallow marine – reef; or of vegetation -swamp Chemical Sedimentary Rocks • Composed of minerals precipitated out of solution (like salt from evaporating seawater). • Looks crystalline (but crystals may be very small. • Classified by composition (minerals). • Ex: Rock Salt, Rock Gypsum Sedimentary Structures (be able to recognize or identify from slide or description) Bedding or stratification • Parallel layers of sediments. • Each layer is called a bed. Cross-bedding • Sets of bedded sediments at an angle to horizontal. • Deposited by currents (wind or water). • Ex: Dunes • Cross-bedding indicates the direction of current. ( opposite of what it looks like) Graded Bedding • Beds progress from coarse grains at bottom to fine grains at top of bed. • Indicates waning of current. ripples • Wavy lines formed on top of a bed of sand or silt by waves or currents. • Smaller scale than larger cross -beds. • Can be preserved in rocks. • Common on shorelines. • Ripples can be symmetri cal (beach) or asymmetrical (dune) Mudcracks • Polygonal pattern of cracks that develop in mud as it dries. • Ex: Mudflats (or other areas exposed to wet/dry cycles). Bioturbation • Burrow marks left in sediments by animals. Tracks and trails • Footprints, etc. left in sediment by animals. Why are sedimentary structures so important? Clues to the past environments (earth history). The present is the key to the past – Principal of Uniformiantarianism Sediments are transported and deposited by one of the agents of erosion - wind, water, ice, or gravity The depositional environment is the geographical area in which the sediment is deposited. Depositional Environments are characterized by a combinat ion of: – sedimentary rock types – sedimentary textures – sedimentary structures present Geologists observe these features in sedimentary rock to determine the ancient environment where the sediment was deposited. Diagenesis - the chemical and physical changes that transform sediment into rock • As sediments accumulate, older layers become buried. • Sediments become compacted and heated. • Sedimentary rocks generally form up to about 10km deep (around 300 degrees C). Lithification - hardening of soft sediments into rock: • compaction – pore space volume is reduced due to weight of overlying sediment, and/or • cementation – chemically precipitated minerals in pore spaces (acts as a glue by binding the materials together) – common cements - calcite, silica, hematite Lecture Outline Friday October 3, 2014 Key Points for today • Understand how water, wind, ice, and gravity affect the size of the sediment being moved • Be able to recognize and name some common depositional environments Common Sedimentary Environments – Continental (Clastic dominates) • Rivers /Streams (fluvial) channelized flow transports sediment. Sand and grain fill concave - upward channel. Fine sand, silt and clay are deposited on nearby floodplains • Desert (minor chemical - evaporite ) Deflation “desert pavement” movement by wind • Lake • Glacial • Alluvial fan – particle size gets smaller and smaller get sand at the bottom. Occur in more die regions • Beach – • Sandstone can be found on continental, beaches, deep sea settings, Shoreline (Clastic/Chemical/Biochemical) • Deltaic (where rivers enter the ocean) • Tidal Flat (exposed at low tide ) • Beach Marine (Mostly Chemical and Biochemical) • Continental Shelf • Continental Margin • Reefs • Deep Sea Clastic Sedimentary Environment Agents of Transport Wind • Most selective agent • Results in well sorted sediments • Sand, Silt or Dust (sand grains may be frosted) Example description: • Very Well Sorted • Quartz Sandstone • Cross Bedding • What environment is it? _______________ Water • Selection and sorting vary. • Depends of strength of currents. • Ex: Faster moving waves on a beach can move gravel s, deeper, grain size decreases depositional environments Glacial ice (highest viscosity) • Least selective • Results in poorly sorted sediments Note: Lack of bedding or other structures. Gravity • Results in poorly sorted - rock avalanche sediments – angular How can you tell if a sediments which forms a clastic sedimentary rock was transported by water or by air? Examples of Clastic Sedimentary Wind transport be able to recognize from a slide) Dunes can form in _____________or _________________ Water transport ( be able to recognize from slide) _____________________ ______________ Fan ________________ _________________ Sandstone can form in all these locations. The particles that make -up the sandstone will vary depending on where they originated and were they were deposited. Ice transport Glacier ______________________________________________________________________________ Biochemical Sedimentary Environments Carbonate deposition • Marine Setting • Limestone and Dolostone • Composed of Carbonate Minerals (Calcite, Aragonite). Property?? Effervescence • Precipitated by organisms or inorganically • Reefs are mound shaped organic structures composed of carbonate skeletons like coral. How Atolls are formed – reefs formed around extinct volcanoes. The volcanoes erode and sink as the ocean plate subsides, but the reef continues to grow at a faster pace than subsidence. Floating organisms also secrete calcium and silica skeletons. When they die they settle to the ocean floor and creating limey and silica rich sediment which can be lithified into sedimentary rocks like limestone and chert. Where does coal come from? Plant material, for example ancient swamps, high production. 50% of our energy comes from burning coal. Where does the oil and gas that we use in cars and trucks come from? Microscopic organisms , if the material doesn’t break down, organic material is made into liquid substance from heat and pressure. We would did for oil where the shell areas were millions and millions years ago. WARM SHALLOW AREA Chemical Sedimentary Environment Evaporite (deserts and marine) • Salts form as water evaporites from a shallow basin. • Forms minerals like Halite an d Gypsum. • Modern Ex: Great Salt Lake , Death valley • Ancient Ex: Mediterranian sea WHAT ROCK LOOK FOR IN OIL? WHAT DEPOSITIONAL Lecture Outline Friday October 3 - Wednesday October 8, 2014 Announcement: Quiz 2 scheduled for Friday October 10 (Interlude B, Chapters 6,7) • What factors control metamorphism? • How metamorphic rocks are grouped or separated from each other? • How are the different types of metamorphic rock textures identified and how they are related to metamorphic grade? • What are index minerals and how are they used? • How do metamorphic rocks fit into the plate tectonic model? - Where do metamorphic rocks form at? Chapter 7 – Metamorphism: A Process of Change Metamorphic rocks – changed rocks – A rock whose mineralogy, texture, and composition (or all three) has changed due to increased temperatures, pressures, or moving fluids (like hot water). The Rock Cycle and metamorphic rocks ___________________________________________________ ______________________________________________________________________________________ Plate Tectonics and Metamorphism – where does metamorphism occur ____________________________ ______________________________________________________________________________________ What happens when rocks get buried? When they heat up? • Delicate features are obliterated • Minerals or grains in the rock may become deformed • Deformation: If buried deep enough, the rock can undergo plastic deformation. • Diffusion: The movement of atoms due to thermal energy (heat) - _________________________ • ________________: Crystals can gro w larger or change shapes. • The mineral grains will become _____________ when acted on by directed pressure – ex. Slate shows "slaty cleavage" Factors Controlling Metamorphism Temperature, pressure, fluids - Hot water can transport ions (chemical weathering). Temperature – as temperature increases • Minerals convert to new higher temperature minerals - Diffusion: The movement of atoms due to thermal energy (heat) – forming the new minerals • Fluids are released Example: clay = mica +H O 2 • Recystallization- crystals grow larger and change shape • Rocks become weaker and easier to form Pressure • Confining Pressure - general pressure applied equally in all directions • Directed Pressure – (differential stress) unequal pressure, greater in on edirection - like converging plates. - The mineral grains will become aligned when acted on by directed pressure • Directed pressure results in foliation – preferred orientation of platy (flat) or elongate minerals. ex. Slate shows "slaty cleavage" - Looks layered Fluids • Released during recrystallization: H O2 CO , p2us dissolved ions • Effects - speed up reaction rates – catalyst - Deposit or remove certain elements, can lead to formation of ore deposits - copper, silver, gold, etc. Classification of Metamorphic Rocks Metamorphic Rocks are classified as foliated or nonfoliated. Foliated Rocks – need to describe the following • Nature of foliation • Size of the crystals • The degree to which minerals are segregated in different mineral bands. These features tell about the Metamorphic Grade of the rock Metamorphic Grade is the degree to which a rock has changed from the parent rock or protolith (original rock type). • Low Grade = Low Pressure and Low Temperature 200 °-400°C (400-750°F). May still contain features of parent rock - fossils, sedimentary structures, etc. • High Grade = High Pressure and High Temperature 500 °-800°C (950-1475°F) - features of parent usually destroyed. Metamorphic Grade increases as Foliated Rocks – directed pressure Rock Name Grain Size Slate (low grade) very fine Phyllite fine Schist medium-coarse Gneiss coarse - minerals in bands Migmatite (high grade) part igneous/part metamorphic Regional metamorphism - review of textural changes observed in mudstone protolith as metamorphic grade increases. (possible exam question) Mudstoneàshaleàslateàphylliteàschistàgneissàmigmatite Non-Foliated Rocks Determine parent (check mineral properties) (possible exam questions) Rock Parent Quartzite Sandstone Marble Limestone - is made of calcite Hornfels fine grained (mudstone) Coal Compressed Organics Why are quartzite and marble generally non -foliated? – not related to pressure , its related to Highest grade of coal (anthracite) moves from the conditions of sedimentary rocks to metamorphic rocks. Regional metamorphism- review of textural changes observed in non-foliated protolith – dominantly _recystallization. Recrystallization: Crystals can grow larger or change shapes. Coal formation and metamorphism • Energy Resource • Forms from the accumulation and compaction of plant materials. • Rapid burial • Low oxygen levels • Ex: Swamps • Lowest grade (peat) is considered sedimentary, highest grade (anthracite) is considered metamorphic. Index Minerals Index mineral are characteristic minerals that define metamorphic zones formed under a restricted range of temperatures and pressures. Ex: Garnet Geologist use index minerals to determine the T and P conditions at which the metamorphic rocks formed. Indicator of metamorphic grade, indicator of protolith. • Prograde path - refers to the T & P path of a metamorphic rock (based on the index minerals) during subduction or burial to higher temperatures and greater depths. • Retrograde path – refers to the T & P path of a metamorphic rock (based on the index minerals) during it journey back to the surface. Types of Metamorphism Contact Metamorphism - Heat from rising igneus intrusions metamorphose pre-exiting rocks. • Low-High Temperatures • Low Pressures regional Metamorphism - Metamorphism caused by deep burial or tectonic forces that increase temperature and pressure over broad regions. (large • Low-High Temperatures • Low-High Pressures • Most common, associated w/ mountain building, intense as “roots” as mountains hydrothermal Metamorphism - Hot water percolates through spaces in rocks. • High Temperatures • Low Pressures Burial Metamorphism - Rocks are metamorphosed by the weight of overlying rocks. • Low Temperatures • Low Pressures Shock Metamorphism – meteorite impact Extremely high temperatures and pressures • Look for Ceosite and Stishovite (shock quartz) – polymorph of quartz, often fractured due to impact • Shatter cone, nuclear explosives are man made shock things… Deformation (Fault) Metamorphism - Rocks along fault planes are crushed and pulverized. • Very Low Temperature • High Pressure Ex: Along the San Andreas Fault Metamorphism and the plate tectonic connection Convergent – regional, _contact, Deformation (fault) Divergent – hydrothermal Transform – Deformation (Fault) Hot spots – Contact, some Hyrdothermal Plate Interiors – Burial Where might you expect to find metamorphic rocks in the US and what type of metam orphic setting did they form in? Convergent boundaries, continent to continent, we expect foliated rocks. Directed pressure creates foliation. Other mountain ranges.. Yellowstone there is hydrothermal possibly contact. None in center of the U.S. Does metamorphism affect any other rock type other than sedimentary rock- mudstone? When u subduct that material there are going to be mostly foliated rocks. So what would happen with a different starting composition - say mafic volcanics? Regional metamorphism: Protolith – Mafic Volcanics - olivine, Results in nonfoliated rocks Why? No clay, other minerals form rather than micas Wrap up – the Rock Cycle revisited Lecture Outline Wednesday. Oct. 8 – 15, 2014 Chapter 10 - Geologic Time Telling time geologically § Earth’s history is concealed in rocks § One of the Goal of geology is to unraveling Earth history Earth’s geologic clock – How do we tell time Absolute dating - determining event’s actual time Relative dating - putting rocks/events in proper order.. newspaper in October Relative Dating: Trying to put rocks in correct order of age without really knowing how old they are. We do this by looking at the physical relationships between the rock units based on their stratigraphy. Stratigraphy- the description, correlation, and classification of strata in sedimentary rocks. Formation is a series of rock layers in a region that has similar physical properties, may contain the same fossils and can be mapped as a unit. Principles of Relative Dating 1) Principle of original horizontality : sediments are deposited in horizontal beds. If rocks do not lie in horizontal beds, they have been disturbed by some kind of tectonic force. Exception: Crossbeds 2) Principle of superposition : In an undisturbed sequence of rocks, each layer is younger than the one beneath it and older than the one above it. 3) Faunal Succession – Fossils as timepieces Use of index fossils to correlate rocks (formations) from different locations Correlation – matching of rock units formations that are the same age. Formation is a series of rock layers in a region that has similar physical properties, may contain the same fossils and can be mapped as a unit 4) Unconformities: markers of missing time (deposition of rocks isn't continuous forever) 1. Disconformity = an unconformity in which the rocks above and below the unconformity are parallel. 2. Angular Unconformity : (in your own words) a period of folding changes the atmerial of the rocks. Then we raise the ocean leve.; and then theres new deposition. Grand canyon 3. Noncomformity : sedimentary rocks in contact with crystalline igneous or metamorphic rocks. (dissimilar rock types in contact with each other) 5) Cross-Cutting Relations: • Dike cross-cuts the pre-existing rock layers. Therefore, it is younger than the rock layers it cuts across. • Fault cross-cuts all rock layers. Therefore, the fault is younger than the rock layers it cuts across. (Block diagram example showing how to handle the relative dating principles) __________________________________________________________________ Please review Figure 10.2 in your text to see how to apply the relative dating principles to construct the geologic history of an area. For additional help, review the Relative Age Dating help document posted on the lecture web page. Key Points for today • How are isotopes used for absolute age dating? • How do you set up a problem and do a simple calculation? • How are fossils preserved and how are index fossils used? • Geologic time 4.6 billion years in the making. What are a few of the important time breaks and why they are important? Absolute Dating Absolute dating provides ages in years. Radiometric Dating- uses _________________________________________ to determine absolute age. The radioactive isotope, the parent isotope, evolves into a decay product, the daughter isotope, at a certain rate. Isotopes: Atoms with identical # of protons, but different # of neutrons. Radiometric Dating The ratio of parent : daughter determines the age of the rock. Half-life of a radioactive element is the time it takes for___________________________________ to decay into daughter product. Not all radioactive elements decay at the same rate, each isotope has a differe nt rate. There are several isotope systems that can be used date rocks and other material (do not memorize, used only for explanation purposes) Parent daughter half life P dating range minerals that can be dated Uranium238 à Lead206 0.7 b.y. 10m.y.-46b.y. zircon and apatite Potassium40 à Argon40 1.3 b.y. 50,000-4.6b.y. muscoviete, biotite, hornblende Carbon14 à Nitrogen 14 5730 yr 100-70,000yr wood, charcoal, water containing dissolved CO2 What we are actually dating is a mineral that contain the isotope of interest. What kinds of rocks can be dated with radioactive methods? - In __________ rocks, the clock begins when the molten rock cools – dates_________________________ (formation) o No parent or daughter atoms added or removed once started the radioactive decay o No resetting with metamorphism (or get time of metamorphism) - For _________________________ rocks radiometric dating gives the age of all the grains which weathered to form the sediments in the sedimentary rocks - For metamorphic rocks radiometric dating gives the age of_____________________ rather than the initial age of crystallization (formation) Example: You find a pluton with a radioactive element with a known half -life of 100,000 years. You collect samples and send them to WSU for analysis. Your results tell you that 25% of the parent isotope remains. How old is the intrusion? Hint: First determine the # of half lives passed. Number of passed half lives x known half life = age of sample. Answer: Parent Daughter Half -life 100 0 ___ 50 ___ ___ ___ 75 ___ ___ half-lives x 100,000 years = ___________years Example: You collect a sample of Granite and it contains biotite mineral crystals so it can be dated using K-40 to Ar-40 decay pair. If there are 1 K -40 atoms for every 3 Ar-40 atoms in the sample how old is the Granite. The half -life of K-40 is 1.3 billion years. Answer: Parent (Ar-40) Daughter (K-40) Half-life 100 0 ___ ___ 50 1 ___ ___ ___ ____ half-lives x 1.3 by = ______ by Carbon 14: Where does it come from and how do plants and animals takein? ______________________________ _____________________________________________________________________________________ _ _____________________________________________________________________________________ _ Reasons why we don't use C -14 in rocks: 1. ________________________________________________. 2. The half-life is only 5730 years, so you can't date anything older than about 70,000 years. Carbon-14 can be used to determine: - Ages of recent lava flows - Ages of recent ash + pumice falls - Ages of recent landslides, lahars Example: You find a piece of charcoal in an ash bed from a volcanic eruption with 12.5% of the amount of C-14 as it had originally. Approximately how old is this piece of wood (and the volcanic eruption that contains it)? Answer: Parent (C-14) Daughter (N-14) Half-life 100 0 0 50 50 1 25 25 2 ___ ___ __ ___ half-lives x 5730 years = ______________ years Review Application of relative age dating principles Youngest Oldest Geologic Time Scale Can be though of as a relative -age calendar of the Earth’s geologic history A key component to constructing the geologic timescale is the correlation of fossils between outcrops. How do we get fossils? Usually _______________________ is required Examples: - Soft mud - Flood deposits - Volcanic ash _______________________________preserve the best (hard parts) - soft body parts don’t preserve well - hard parts usually undergoes ___________________________. Petrified Wood: Plant cells have been replaced by quartz (SiO2) {many are buried in volcanic landslides or eruptions} Most bones have been replaced by mineral s Trace Fossils: Evidence that the organism was there, although the organism is gone. Casts + molds of footprints Burrows- The burrowing animals are gone, but their burrows remain. Index Fossil : - used to identify the relative age of a rock unit - used in stratigraphic correlation of rock units from one location to another What makes a good index fossil: - Unique and easy to identify - Lived for a period of time (preferably only thousands to hundreds of thousands of years) - widely distributed Geologic Time Scale Can be though of as a relative -age calendar of the Earth’s geologic history 1. Time is divided into Eons, Eras, Periods, and Epochs 2. The time between each division is NOT the same. Geologic Time Scale was constru cted by: 1. Determine the relative ages of sedimentary rocks by simple rule of superposition (relative age dating principles) and by local and global fossil record. 2. Can use deformation and angular unconformities to date tectonic episodes in relationship to the rock sequence. 3. Can use cross-cutting relationships to establish relative ages of igneous bodies or faults cutting through the sedimentary rock. 4. The geological time sale is a worldwide effore The geologic time scale is a worldwide effort by geoscientists spanning over 150 years. • In the last 50+ years, absolute age dating methods are used to refine the time scale. • The time scale is still being refined and updated. For a quiz or exam you need to know the Eon and Era designation. Eons Phanerozoic - last 543 million years Eras Cenozoic - recent life (youngest) 0-65 mya (mammals, humans) Mesozoic - age of middle life 65-251 mya (dinosaurs, 1st small mammals) Paleozoic - ancient life (lots of reefs, ammonites) 251-543 mya (fish, trilobites, clams, corals, ferns ) Precambrian - from birth of Earth (4.6by) up to before complex life forms developed (greater than 543 m.y.) (algae, bacteria, some fossils without shells like jellyfish) Which geological time period covers approximately 88% of all geological time = Precambrian A very brief history of life on Earth The rest of the lecture period addresses the history of life on Earth. The bulk of the material presented is not in the text book and you are only responsible for the information that answers the following questions. Questions: Approximately, when was t he earliest evidence indicating life existed on Earth? 3.5 bya First evidence of liquid water 3800 mya. First hint of life comes from banded iron formations deposited What form did early life take? Single cell organisms Cynobacteria. Stromatolotes: stumpsixed colonies of synobacteria Why is the time break between Proterozoic (Precambrian) and the Phanerazoic (Paleozoic Era) placed at 543mya? This is the first occurrence of shells. What changes are noted in the fossils that exist during this break ? They had hard shells. Criniods (also called sea lillties) these are filter feeder animals not plants. First fish At the end of what Era were all landmasses united to form Pangea? 306 MYA Paleozoic. Vast coal swamps at equator. First amphibians on dry land at end of middle Paleozoic. Turned int o reptiles; can lay eggs on land – first appear in the late Paleozoic. Reptiles are in the air, land and sea. What event marks the Paleozoic – Mesozoic boundary? First land animals in early Paleozoic, Its marked by thte greatest mass extinction of all times, about 90 % marine and 70% land animals. Hypothesis, meteorite impact or expelling vast amounts of basaltic lave – flood basalts What happened? What is the dominate life form in the Mesozoic – Dinosaurs are not reptiles What Era did the dinosaurs flourish? Late Paleozoic What event marks the Mesozoic – Cenozoic boundary? What happened? What was the name of the impact crater in the Yucatan Peninsula, Mexico? The presence of what element supports an impact hypothesis? The ancestors to modern man, Homo Sapiens Sapiens, first appeared approximately how many years ago? Lecture Outline Friday October 17 thru Wednesday October 22, 2014 Questions? Lecture Exam Friday October 24 • Same time, Same room • Bring Pencils and WSU ID • 50 question Multiple Choice, Computer Graded • Interlude B,E; Chapters 6,7,10,9 • Study Guide and review slides are on-line Exam 2 study session in Webster 16 Mon. October 20 from 6 -7pm - Erika Rader from 7-8:30pm - Kurt Wilkie Key Points for today • What are the different types of stress and strain and how do you recognize them. • How can you determine the fault type from one another? - Which side is the hanging wall? - Which side is the footwall? • What does the strike and dip of a rock tell us? Chapter 9 – Crags, Cracks, and Crumples: Crustal Deformation and Mountain Building Structural Geology - The branch of geology devoted to crustal deformation and the creation of non - volcanic mountains. Understand the difference between map view and cross -section view (profile view). Rocks under Stress are deformed or Strained. stress – force acting on the rock strain – the resulting change in shape or volume Types of Stress • Compression - Where rocks are compressed or pushed together. Convergent Boundaries • Tension - Where rocks are pulled apart, away from one another. Divergent Boundaries, zones of Continental Rifting • Shear - Rocks shift past one another in a horizontal motion. Transform Boundaries Strain When a rock is stressed it may become deformed, changing in shape and/or volume = strain. Types of Strain (Deformation) Elastic deformation • Temporary strain, goes back to original form when stress is released. Brittle failure • Permanent strain, cracks or fractures (faults). Plastic deformation • Permanent strain, Flows and bends (folds). Faults Brittle failure results in cracks or fractures in rocks. If no movement has taken place along the fracture, it is called a Joint. If movement has taken place along the fracture it is called a Fault. The fault plane is the surface along which movement takes place. Types of Faults Strike slip faults – Side to Side (Horizontal) Motion. Result of Shear stress. – Left-lateral – Right-lateral Dip-Slip Motion is up – down (vertical motion) along the fault plane; caused by compression or tension. - Reverse (compression) - Normal (tension) • The easiest way to determine the type of vertical motion is to see a cross -section (side view). • Based on relative motion. • Draw a stick figure across the fault plane! Normal – Headwall moves down . = Tension Reverse – Headwall moves up . = Compression How to determine fault type • Is the motion vertical or horizontal? – Can the motion be seen in a cross -section or map view? • If horizontal (map view) - right or left motion? – Right-Lateral Strike Slip Fault – Left-Lateral Strike Slip Fault • If vertical (cross-section view) - HW has moved up or down relative to FW? – Normal (HW down relative to FW) – Reverse (HW up relative to FW) Faults, Stress and Strain All faults are an expression of Brittle strain but each result from different types of stress. Fault: Reverse (headwall moves up) Normal Strike slip -Rightlateral Stress: Compression Tension Shear Plate Tectonic: Convergent Divergent & Rifting Transform Other fault types: • Thrust - _____________________________________________________________________ • Continental Rifting – normal faulting • ________________________ – combining strike slip and normal fault motion Key Points for today • What are the different types of folds and how do you tell them apart? • How do oil and gas deposits form? Where and why does oil and gas accumulate in certain area? • Are there any alternatives to a hydrocarbon based energy sources? ----------------------------------------------------------------------------------------------------------------------------- ---- Review: Name the 3 types of stress: What type of strain (deform ation) do we see in rock? What is the difference between a faults and joints? Strike slip faults – side to side horixzontal motion. Result of shear stress ---------------------------------------------------------------------------------------------- --------------------------------- Geologic information is recorded on maps and includes rock types, the orientation of the rock units, folding and faulting information. All this information is used to create cross -sectional (profile) Strike & Dip: A way to measure rock orientation. Rocks are originally horizontal. With added stress they tilt, fold or fault. Strike – Direction of the intersection of a rock layer with horizontal surface. Dip – the angle of tilting (from horizontal) Strike and Dip Symbol FOLDS - Folds result from compression (ductile or plastic deformation) Most folding occurs at depths where the temperature and pressure are much higher and the rocks can bend without fracturing. Folds • Folds form when rocks are formed. They are a structural feature, different than a hill or valley (which may form only from erosion). • Generally, folds form when rocks undergo plastic deformation (type of strain) from Compression (type of stress). • At what type of plate b oundaries would you expect them to be associated with? __________________ Types of Folds Syncline • down arched fold (like a “U”). • Youngest rocks found at the center of the fold (near axis) Anticlines • up arched folds (like an “A”) • Oldest rocks found at the center of the fold . Parts of a fold (in your own words describe) • Fold axis – imaginary line that divides a fold along its surface • Axial Plane – a imaginary plane that divides the fold symmetrically as possible • Limb – half of the fold Fold Axis • Horizontal Fold Axis • Plunging Fold Axis – axis dips into the Earth Horizontal axis Plunging axis Fold shape Symmetrical folds - beds have about the same dip in each limb Asymmetrical folds - beds in one limb dip more steeply than the other Overturned fold - have limbs that dip in the same direction What do folds look like on the surface (map view)? • Syncline: Horizontal Fold Axis – Series of parallel stripes! • Plunging Fold Axis: Beds are not parallel they converge Look like folds on top (If lines are parallel


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