Geology 1610 notes for exam 2
Geology 1610 notes for exam 2 GEOL 1610
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This 9 page Class Notes was uploaded by Olivia Brooksbank on Friday March 4, 2016. The Class Notes belongs to GEOL 1610 at University of North Texas taught by Johnny Byers in Spring 2016. Since its upload, it has received 65 views. For similar materials see Physical Geology in Geology at University of North Texas.
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Date Created: 03/04/16
Notes: Metamorphism 2/22 Metamorphic rocks: - Sir Charles Lyell: From the latin - Came up with Metamorphosis: to change - The transformation of pre-existing rock from igneous, sedimentary, or metamorphic origins through a continuum of change - Three primary agents of metamorphism: HEAT, PRESSURE, CHEMICAL/FLUIDS - Ultimate sources of heat energy are: EARTHS INTERIOR and STRESS from PLATE TECTONICS - Two scales of Metamorphism: REGIONAL, CONTACT - (Country rock that comes into contact with magma chambers, heated) Major settings of metamorphism: Regional Contact or Thermal Fault zones Impact Hydrothermal Burial Regional - Large Scale, highest degree of metamorphism where the rocks collide - - Gneiss > Schist > Phyllite >Slate: High to low grade metamorphism Contact metamorphism: Large scale, Sharp, highest degree Regional Metamorphism degree from low to high: 1. chlorite rich rock 2. biotite rich rock 3. garnet rich rock 4. starlight rich rock 5. similinite rich rock 6. igneous rock Tishomingo granite intruded by mafic dike > SHARP contact metamorphism Fault Metamorphism: (Fault zones) - (Ex: Pacific plate and North american plate collide, fault) - Can be high or low grade - Light and dark minerals that segregate, line perpendicular to lines of stress (busy) - Echelon Fault: Low grade metamorphism (less busy) Impact Metamorphism Meteor Crater:Arizona, aka Barringer Crater - 5 impact craters identified in Texas - Meteor made of iron and nickel smashes into earths surface - Chicxulub Hydrothermal: - Elements deposited by solution when waters are heated by nearby magma chambers. - As the water cools when moving through the subsurface the elements precipice out - (Vein of quartz rich in silver…Native copper) Hydrothermal Minerals: Sphalerite = Zinc Galena = Lead Chalcopyrite = copper Bornite = copper Magnetite = Iron Talc = talc Graphite = Lead Notes: Metamorphism 2/22 Burial Metamorphism: - Coal is sedimentary rock - The process by which coal beds form begins with the deposition of vegetation - Pressure to Coal into anthracite coal that is dent and fuels the industrial revolution - Deform sedimentary rock Agents of Metamorphism: - Heat - Deeper into earth the HOTTER it will get - Pressure - Deeper in the earth the HIGHER the pressure will be - Fluids:Accelerate chemical reactions, become hot enough they force up to the surface of the earth, dissolving atoms and ions dissolved in fluid can migrate through a rock and react with solids to form new minerals Increasing Pressure and Temperature: - Low Heat and pressure: Low grade metamorphic rocks - High Heat and pressure: High grade metamorphic rocks - In-between Two groups of metamorphic rock - Difference is the chemical composition - FOLIATED: Different minerals come out at different temperatures - NON FOLIATED: Only one mineral, calcium carbonate (example: sandstone into quartzite; and marble) Textural Terms for Metamorphic rocks: Reflects the degree of metamorphism - Salty - Phyllitic - Schistose - Gneissic APolymorph: DIFFERENT FORMS Different degrees of metamorphism: same chemical signature BASED ON HEATAND PRESSURE! - Kyanite (Low degree; Grade) - Sillimanite (medium, Grade) - Andalusite (high degree, Grade) Index Minerals: - Used to estimate the degree of metamorphism - Quartz and Feldspar > not good index minerals Change of minerals with increase pressure and temperature: Chlorite Muscovite biotite < Increasing metamorphism (Low to high) garner staurolite sillimanite Notes: Metamorphism 2/22 INCREASING METAMORPHISM: Shale - Shaly Texture (Layers) (PAIRING MATERIALFOR SLATE) - Formed by consolidation of clay, silt or mud - Characterized by finely laminated structures Slate - Slaty Texture (Cleavage) - Slate - Chlorite starting to glow - Exhibits rock cleavage - Harder than shale - more sheen - NO fossils - Denser than shale Slate USES: because of cleavage - Pool tables - rooftops Phyllite - Phyllitic - Mica starts to grow - More sheen than slate - Microscopic crenelations - Platy material (micas) - Larger than shale but not visible Schist - Schistose (higher degree of meta) - Visible mica - Index materials - Schistose texture (leafy) Gneiss - Gneissic (even higher) - Separation of dark and light minerals - Augen - eyes (MORE pressure) Migmatite - partially melted metamorphic rock - Melt at low temp. liquefy first and will flow - If majority of the rock melts and refreezes it becomes igneous! WHO WILL MELT FIRST > FELDSPARAND MICA Granite Gneiss - Look for sharp boundaries between minerals Non-Foliated or Granoblastic Foliation is absent Crystals grow in equant shapes such as cubs or spheres DEFINED BY COMPOSITION INSTEAD OF TEXTURE (Ex: massive, solid, one piece, altogether) Marble - Calcium carbonate pressure Quartzite - Silicon dioxide rich sandstone Notes: Metamorphism 2/22 Parent Metamorphosed Rock Foliated: - Shale, sandstone = slate, phylite schist, Gneiss Non-foliated - Quartz rich sand = Quartzite - Limestone = Marble - Basalt = Greenstone What drives metamorphism? - PLATE TECHTONICS Friday special Alayer of rock and mineral fragments that covers the earths surface is called REGOLITH (LAYER OF ROCKSAND MINERALS THAT COVERS THE EARTHS SURFACE) The US can be divided into two generalized soil type areas. Which of the following are generalized area types? Pedocal and pedalfers Amigmatire rock that has undergone partial meltingg It is approx half igneous and half metamorphic - TRUE Which of the following is not one of the three things that effect the rate of weathering and the formation of soils - Consistence You are testing a sedimentary rock for SiO2 cementation the defensive test would be…? - Scratching of glass Mass Wasting 3/2/16 Mass Wasting: The dislodgment and down slope transformation of soil or rock under direct application of gravitational stress Gravity = Primary Control Water = amount present - Adds mass - Makes clay slick Slope =Angle of repose Classification of Mass Wasting process: - Type of material: Debris, mud, earth, and or rock - Type of motion - Slide = Cohesive materials (dirt, rock, and debris) - flow = Fluid type motion - Fall = free fall in response to gravity - Rate of movement - Slow or creep, imperceptible movement - Floating on air (125 mph) Mass wasting events: - Slump = coherent mass of loose consolidated materials or rock layers moves short distance down slope - creep = slow adjustment of soil and rocks to make fenceposts shift out of alignment, or phone poles - rock slides - landslide or earth flow - mudflow or debris flow - rock fall - Solifluction (Freeze, lifts up and expands soil and when melts it drops back down) Chapter 6: Our Earth Is Dynamic: - Plutonic, Volcanic, and orogenic forces are constantly elevating parts of the earth - opposing forces are removing materials from higher elevations - ALL materials are subject to weathering Terms: - Geomorphology = the study of landforms, their origin, evolution, form, and spatial distribution - Denudation = any process that wears away or rearranges landforms - Base Level = a level below which a stream cannot erode its valley further (Ultimate base level: Sea Level) -eathering: When rock is broken into increasingly smaller parts, each maintaining the characteristics of the original material. - Mechanical and Chemical - Mechanical: Accomplished by physical forces, increasing the amount of surface area exposed to the weather’s destructive power (Primary agent of mechanical weathering is WATER) Examples of mechanical Weathering: - FROSTACTION - SALT-CRYSTAL GROWTH - SOLUTION - POTHOLES - EXFOLIATION - OrganicActivities Mass Wasting 3/2/16 Frost Wedging - Frozen water freezes and pushes rock apart Salt crystal growth - Sandstone, water goes through it, salt goes into solution Breaking Down: - Clams attach to stone, it has an acid footprint that go into bedrock and break it down - Ants bring fine grains to the surface and cause heavier grains to settle down Chemical Weathering - Complex processes by which rock components and internal structures are broken down, converting the constituents to new minerals or releasing constituents into surrounding environment - WATER IS THE MOST IMPORTANT WEATHERINGAGENT Rainwater: - The burning of fossil fuels (coal and oil) releases sulfur into the air that combines with oxygen to for sulfur dioxide - Exhausts from cars cause the formation of nitogen oxides in the air - From these gases, airborne sulfuric acid and nitric acid can reformed and be dissolved in the water vapor in the air - Acid Rain gasses may originate in urban areas, but are often carried for hundreds of miles in the atmosphere - BURNING FOSSIL FUELS =ACID RAIN Examples of Chemical Weathering - Dissolution: Carbonic acid organisms and dead stuff - Hydrolysis: Creates Spheroidal weathering (caused by hydrolysis, shape) SHAPE THAT RESULTS FROM CHEMICAL WEATHERING, cleavage of chemical bonds by the addition of water - Oxidation: Oxygen, rust Notes: Sedimentology 2/24/16 Sedimentary - Latin = sedimentum = settling. The study of sedimentary rocks, the process by which they were formed, the description, classification, origin, and interpretation of sediments - 75% Of all rocks out cropping are sedimentary (The product of weathering) - By volume, 5% of outer 10 miles of the Earth’s surface are sedimentary - Current erosion rates: How fast rock will erode based on the type of sedimentary rock it is If the earth were not so dynamic erosion would make it perfectly round and water level would rise Sedimentary rocks provide us with CLUES we need to interpret the Earth’s history - Provenance = Origin - Distance of transport (rounded or angular) - Water, gravity, ice, Eolian (wind) : (Method of Transport) To reconstruct ancient environments we have to look at lithology in two different ways SPATIALVS TEMPORAL - Spacial - Times and conditions in one particular area (Looking at change through time!) - Temporal - Ho wit evolved through time comparing several outcrops (SPACE and TIME are tied together using correlation) Temporal Correlation - Different locations - uniformitarianism - Super positioning - Fossils - Tie locations together - Count upward through time Three basic Types: Detrital - Sandstone, Conglomerate, shale (Glued together) Chemical - Limestone, dolomite, travertine (Calcium carbonates) Organic - Coquina, chalk, lignite (Plant and animal matter) How to classify sediments Texture - How big particle is and what it looks like Composition - What it’s made of Physical clastic rocks - Terrigneous deposits that consist of fragments of pre existing rocks which were transported and deposited by Physical Processes - Identified by particle size/grain size - Lithification = processes that Compact, Consolidate and Cement rocks together Lithification process: COMPACTION - Sediment particles from preexisting rocks shushed together CEMENTATION - Deposit solution around the grains, (WATER BEST SOLUTE) glues together FIVE COMMON TYPES of cements - Calcite - silica - Limonite - Hematite - Glauconite - green Notes: Sedimentology 2/24/16 Physical or clastic sedimentary rocks are named based on particle size Mudstone and Claystone > often called shale Siltstone > called shale sometimes Pebble Stone: small > Conglomerate: rounded, well traveled sediments Cobble stone: bigger Breccia: - Broken rock physically weathered off of, cliff face, gravity pulls it a short distance, accumulates, compacted and glued together HIGH ENERGY SHORT DISTANCE! Well sorted material: - Traveled a good distance - Some physical action that separates these grains - Stream channel Chemical Rocks - Minerals precipitation out of the water column and glued together by chemical processes - Composition - what they are made of - Texture - Direct precipitation > Evaporites Chemical sedimentary rocks are named based on composition and texture Allochthonous sedimentary rocks that were formed from transported sediments Autochthonous are formed in place Examples o chemical sedimentary rocks that can be of organic origin - Halite - Gypsum - Calcite - Limestone - Dolomite Common elements found in Sea Water: - Ca - K - Na - SO4 - CO2 - O - Mg - H Biological rock - Chalk THE MOST OBVIOUS FEATURE OF SEDIMENTARY ROCKS IS THE LAYERING Primary Structure - Deposition, environmental to interpret the medium whom carried the rocks Primary Structures: - Notes: Chapter 6 3/4/16 Soil is NOT dirt: Ways of thinking about soil: - Medium for the growth of plants - The epidermal unit of a geologic body of material through which all material must pass in the erosion cycle from rock to sediments - Unstable entity, slow-motion whirlpool of mineral and organic matter - Abeautiful, if not mystical blend of the forces of life and death - Main component of Mother earth Soil: - Naturally occurring, unconsolidated or loose material on the surface of the earth, capable of supporting all life (All human, animal, and plant) - Soil forms the Pedosphere (the interface between the lithosphere, biosphere, atmosphere and hydrosphere - Unit of study is the PEDON, a three dimensional sample of the surface - Soil profiles are used to describe PEDONS Hans Jenny: - Soil = function of the (ClORPT) - Cl: Climate - O: Organisms (plants and animals) - R: Relief (change in elevation) - P: Parent Material (Dominant control on what type of soil we have) - T: Time (Stability and Weathering) STABILITYAND WEATHERING - You have to have a stable surface: 0 deposition, you reset it when you pick it up and bury it again Horizonation: - Alayer of soil, approximately parallel to the soil surface, with characteristics produced by soil-forming processes - Field approach to horizons (take samples and evaluate color) - color (most diagnostic) - Texture: the mixture of sand, silt and clay (Gritty? Smooth?) - Structure: Distinctive structures based on texture and rainfall (blocky, angular, granular) - Clay films: go down profile first, smallest and coat faces (USE THISASAN INDICATOR OF HOW MUCH WEATHERING HAS TAKEN PLACE) - pH/concretions - Mottles: Tells us about water table, colors, fluctuating water tables by color - Korotovina - Boundaries: Clear and parallel to the surface tells us how soil is intact