Course Notes
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Course Notes GEOL 1301: Course Notes The following are copies of text used in class PowerPoint presentations (pictures not included). They are NOT intended as a substitute for attending class. Other information will be presented in class, this is NOT a complete set of class notes. INDEX Mineral Properties Atoms Mineral Structure Igneous Rocks Sedimentary rocks Depositional Environments Metamorphic rocks Weather Geologic Time Solar System Precambrian Paleozoic Mesozoic Cenozoic Mass Wasting Rivers Groundwater Deserts Glaciers Oceans Structures Earthquakes Earth's Interior Tectonics INTRODUCTION TO EARTH SCIENCE Why study geology? This course studies: earth's materials, changes on the surface and interior, dynamic forces that cause those changes Important Concepts: Geologic Time: earth very old (4567 million years old) Processes Repeat - can study the past to understand the present and vice versa Plate Tectonics: entire earth is moving; earth's surface layer broken into PLATES = slabs of LITHOSPHERE moving due to mantle convection ----- due to earth's internal radioactivity & gravity 3 major types of plate boundaries: divergent, convergent, transform MINERAL PROPERTIES (Return to Index) Definition of a mineral: natural, crystalline solid, narrowly defined chemical composition, not made by life Mineral properties: most useful are those that are controlled by internal arrangement of atoms &/or main composition Crystal Form -- = shape mineral grows in, when grows freely * characterized by angle between flat surfaces Growth Habit -- distinctive crystal form, ex., pyrite Minerals usually grow into available space - so don't show crystal form. How minerals break - controlled by internal structure & bond strength If break along >1 flat surface = cleavage If break along irregular surface = fracture count number of flat surfaces = cleavage planes Page 1 Course Notes 1 Direction: ex., Mica, graphite 2 Directions: (“stairstep”) that intersect @90º: feldspar, pyroxene or (“rooftop”) intersect not @90º: amphibole 3 Directions: cubic = @90º: halite, galena or rhombohedral = not @90º: calcite 4 Directions: fluorite, diamond 6 Directions: sphalerite Fracture = mineral breaks along an irregular surface: quartz *Luster* = way mineral reflects light metallic - looks like metal: galena metallic minerals are usually very heavy and are never see through vs nonmetallic - may be shiny, may not, doesn't look like metal ex., quartz Minerals are not color coded! Exceptions: azurite, malachite Color limited usefulness since can be due to a variety of reasons ex., to trace elements or to small errors in crystal structure will just split minerals into USUALLY dark or light colored *Streak* = color of powdered mineral especially useful for metallic minerals brown ex., hematite - streaks red- *Hardness* = how easy/hard is mineral to scratch test relative hardness by scratching one mineral against another Mohs Hardness Scale softest = 1: talc 2: gypsum (fingernail) 3: calcite 4: fluorite 5: apatite (glass, nail) 6: feldspar 7: quartz 8: topaz 9: corundum 10: diamond Split minerals into Hard (scratches glass) and Soft Minerals close to glass hardness are listed as hard, but may not scratch. How hard are your teeth? Rocks are often 6 & 7 *Density = mass/volume -- how heavy it feels Specific Gravity: ratio of density/density of water (1 g/cc) Feels light = less than c. 2.4 Feels “normal” = 2.5-2.7 Feels heavy = over 2.8, especially if over 3.5 very useful for some minerals Tenacity = resistance to breakage etc. some minerals are elastic - ex., mica or malleable, ex. copper Iridescence - ex., opal, tiger's eye Luminescence - includes fluorescence = glows in ultraviolet light and phosphorescence= glows in visible light Will the mineral transmit light? Transparent = can read through it vs Translucent =can see through it vs Opaque can't see through it Magnetism - ex., magnetite Taste - ex., halite Smell - ex., sulfur Reaction with acid - ex., calcite Atom Lecture All matter made of ELEMENTS 90 natural (Return to Index) = smallest can split substances into using chemistry Page 2 over 100 known, over Course Notes but only 8 common in the earth's crust = O, Si, Al, Fe, Ca, Na, K, Mg entire earth mostly made of only 4 elements = Fe (iron), O (oxygen), Si (silicon), Mg (magnesium) individual piece/particle of an element = ATOM Atoms = very small, c. 10-8cm across (=0.00000001) *vary in size so only some will fit in certain crystals are made of SUBATOMIC PARTICLES Protons: mass, positive charge # protons = ATOMIC NUMBER dictates element name Neutrons: mass, no charge # protons + # neutrons = MASS NUMBER Electrons: no mass, negative charge same number of electrons & protons in atom controls chemistry Isotope: varieties of atom - different mass number, same atomic number, some radioactive Models of Atoms Energy-level shells (orbitals): 1st = lowest energy, holds 2 electrons max; 2nd = more energy, holds 8 max, etc. Noble gases - full outer shell = chem. stable share electrons to reach chem. stable full outer electron shells other atoms lose, gain, or How do atoms bond together in a mineral? Atomic Bonds: control many mineral properties; most minerals held by more than one of 4 types Ionic: electrons transferred. electrical attraction between ions; covalent: electrons shared; metallic: electrons shared, plus "extra" electrons; van der Waals: asymmetric shape MINERAL STRUCTURE (Return to Index) orderly arrangement or crystal structure of atoms dictates many of its properties. •depends on packing arrangement of large atoms •anions are largest grouped by anions •mineral name based on crystalline structure 2 minerals with same comp. but different. structure = polymorphs ex., Diamond and Graphite over 4000 minerals known but only 20 common = Rock-forming minerals SILICATES: most common based on silica (SiO4 )4- forms into 4 sided pyramid = tetrahedron uses: cement, glass, etc. Balance negative charge •combine w/cations, ex., olivine (Fe,Mg)2 SiO4 or polymerize forming chains, sheets, or networks by polymerization: Share oxygens to link tetrahedra single chain silicate - 2 oxygens shared tetrahedra, chains held to other chains by cations cleavage (contrasts in bond strength) Double chain silicates: 3 oxygens shared/tetrahedra, chains held to each other by cations, cleavage Sheet silicates: sheets bond w/cations ex., clay, micas; cleavage 3-d framework silicates: all 4 oxygens shared, quartz (SiO2 ), no weak bonds = fracture Ex.: Feldspar: Na(Si3 Al)O8 or Ca(Si2 Al2 )O8 or K(Si3 Al)O8; 2 directions of cleavage Feldspars = most common mineral silicates: ferromagnesian (have Fe, Mg), nonferromagnesian (don't have Fe, Mg) OXIDE = cations + O2- heavy, ores Ice H2 O magnetite Fe3 O4 hematite Fe2 O3 Niobium, Tantalum,Al, Mo.... Page 3 ores: Cr, Mn, V, Sn, Course Notes SULFIDE = cations + S2- also heavy, ores Galena PbS pyrite FeS2 Hg, Mo, Ag,.... ores: Cu, Pb, Zn, Ni, Co, CARBONATE = cations + (CO3 )2- (compound ion) use = cement, fight acid rain.... calcite CaCO3 dolomite CaMg(CO3 )2 PHOSPHATE = cations + (PO4 )3- use = fertilizer Apatite Ca5 (PO4 )3 (F,OH) SULFATE = cations + (SO4)2- use = plaster, wallboard Gypsum CaSO4 •2H2 O anhydrite CaSO4 HALIDE = cations + halogen elements (Cl, I, Br, F) Halite NaCl Fluorite CaF2 Mineraloid Opal - amorphous (=not crystalline) SiO2 •H2 O or Limonite (hydrous iron oxide) or Bauxite = mix of minerals, Al ore, forms in soils Native elements: graphite, diamond, gold, silver, copper, etc. Mining: potentially dangerous to environment, RRR Rocks = aggregates of minerals and explained by ROCK CYCLE 3 major types: sedimentary, metamorphic, igneous, linked IGNEOUS ROCKS (Return to Index) Most of Earth, associated with hazards and resources from melt, form at high T ---- Igneous lava (volcanic), magma (plutonic) Volcanic - or extrusive, form on surface Plutonic - or intrusive, form underground, later exposed by uplift and erosion Observations: • Temperature: HOT! 1000-1200ºC • Flowing LIQUID Silica >50% Silicate Minerals • Composition: most common (in crust): c. 50% Silica ---- Basalt c. 60% silica ---- Andesite c. 70% silica ---- Granite most common in mantle: <45%, peridotite • Speed & Ease of Flow VISCOSITY = resistance to flow controlled by: Amount of Silica Lots = Viscous Temperature Low = Viscous Volatiles Lots = Fluid & Explosive = gases, liquids = CO, H2 O, CO2 IDENTIFICATION OF IGNEOUS ROCKS Texture: size, arrangement of minerals - controlled by cooling time (& volatiles) vesicular: volatile escape holes: pumice & scoria glassy = super-fast cooling, elements frozen, no mineral crystals formed: obsidian phaneritic = slow cooling, minerals >3mm, plutonic aphanitic = fast cooling, minerals <3mm, volcanic porphyritic = mix of cooling stages then I.D. minerals in the rock (if visible): silicates, use shape and color VOLCANIC LANDFORMS vents, craters Page 4 Course Notes cones: 3 major types - differ in size, shape, hazards, rock types and locations Shield: long-lived --- large; low silica lava --- low slope <10degrees fluid mafic lava flows hazards: to structures, volatiles, landslides Cinder: small, steep, erode fast, short-lived layers of pyroclastic materials --- symmetrical, 25-35 angle of repose hazards: volatiles, pyroclasts, local only mostly made of scoria (pumice) Composite or stratovolcanoes: long-lived --- large, symmetrical, steep pyroclasts, viscous lava made from high silica (60-70%) magma = intermediate to felsic forms andesite and rhyolite (granite), very viscous most dangerous: pyroclastic flows (nuee ardante or fiery ash clouds) high speed, toxic, suffocating landslides: steep + moisture+unstable rock + earthquakes Vesuvius, Mt St Helens March 1980: warnings: steam, earthquakes, bulge...evacuations 2 months: small eruptions, bulge grows, quakes.... 8:32 AM, May, 1980: 5.1 quake --- landslide --- eruption 4,700 million board feet timber leveled/killed; 57 people killed Mt Mazama (Crater Lake): grew (12,000ft), blew (6875b.p.), fell, filled formation of caldera, resurgent cone Jemez Mtns: Valles Caldera, pyroclastic flows Thunderbird Formation & Red Bluff Granite, 1100 million years old maar: magma heats groundwater --- steam explosion fissure eruptions, sea floor formation & pillow lavas geysers & hot springs fumaroles - vplatiles, clues to future eruptions Galeras erupts IGNEOUS ROCKS & TECTONICS Prediction of volcanic eruptions: volatiles, tremors, tiltmeters, history only 10% of 1300 active volcanoes monitored Plutonic Landforms visible through uplift & erosion classify by size, shape, relation to surrounding rocks dike, sill, neck, laccolith, stock, batholith largest = batholith Source of magma source of heat: radioactive decay, transferred via convection locate @ plate boundaries (hot spots) magmatic differentiation melting = F(amt. silica, water, T, 1/P) Bowen's series Formation of magma @ divergent boundaries: decompression melting partial melting of upper mantle (lower crust) due to release of pressure + rising mantle formation of ocean crust; shield volcanoes, fissure eruptions features indicate fluid lava: T high enough, P low enough to melt low silica minerals rocks formed: mafic @ convergent w/subduction: P increases + amt water increases + small T increase partial melting of crust & upper mantle --- intermediate to felsic magmas andesite & granite --- composite volcanoes --- continent crust made @ continent-continent convergent: generally not hot enough no subduction: P increases + small T increase + no additional water = no volcanoes crust thickens @ transform: generally not hot enough P increases + slight T increase + no additional water = no volcanoes @ hot spots: rising mantle plume T increase -- mafic volcanics -- shield volcanoes & fissure eruptions under continents: variety volcanics (plume melts part crust) -- super volcanoes & hot springs, ex., Yellowstone SEDIMENTARY ROCKS (Return to Index) Page 5 Course Notes Why study sedimentary rocks? - only 5% of crust volume; covers over 90% of surface evidence of environment - may contain fossils - Economic value: oil, coal, diamonds, gold, cement........ - record How do they form? Through the sedimentary rock cycle: Weathering - breaks rocks into pieces - through chemical reactions & mechanical action, like growth of ice or salts, fires, roots, etc Erosion - removes sediment Transportation of Sediment via water or wind or ice (glaciers) when movement slows/stops: sediment is --Deposited - varies by environment Burial --- Diagenesis = Lithification = cementation (common cements: silica, calcite, hematite) + compaction (as much as 60%) +/chemical alteration End result = sedimentary rock Divide sedimentary rocks into 2 major groups: clastic and chemical: based on how material was carried. CLASTIC ROCKS (DETRITAL) = rocks made of pieces = clasts = detritus clasts = particles/grains of minerals +/- rock fragments +/- fossils Transported as visible pieces, show signs of wear (abrasion) are held together by cement between grains CHEMICAL SEDIMENTARY ROCKS = materials transported in solution, not visible when transported show no sign of wear, so have different textures, form when precipitate out of water ID largely by composition How to name a sedimentary rock First: texture - clastic //or for chemical: crystalline, bioclastic, compressed or oolitic For clastic rocks: name dictated by GRAIN SIZE Grain Size "coarse", that is, >2mm Rock Name if angular -- breccia The longer the granule, pebble, cobble, boulder transported, the sand-size (0.0625-2mm) smaller the grain size will be. silt-size (0.0039-0.0625mm) mud or clay-size (<0.0039mm) if rounded -- conglomerate sandstone siltstone mudstone or shale (if fissile) Can get other information about transport or deposition from other textural characteristics, likeSORTING: describe sorting by # of classes seen poor: mix of > 2 sizes transported short distance moderate: 2 grain sizes present farther transport well: all one grain size long distance of transport Sorting varies by transporting agent water -- sorting increases with distance of transport wind -- deposits well sorted sediment ice & landslides -- deposit poorly sorted sediment Sorting may also be by density or by durability Page 6 sediment is Course Notes PARTICLE SHAPE: particles start with lots of sharp corners due to mechanical weathering become smoother and smoother with increasing distance of transport. Geologists say "more rounded." ARRANGEMENT OF CLASTIC GRAINS porosity = % of pore space in total volume of rock rock to transport fluids permeability = measure of ability of COMPOSITION OF CLASTIC SEDIMENTARY ROCKS (Return to Index) Rock Type Composition Breccia Conglomerate rock fragments Sandstone Quartz SS > 75% quartz grains - varies - stable minerals most common - unstable only found close to source - common in beach & desert, with long transport Arkosic SS >25% feldspar + quartz - less chemical weathering - less transport Lithic SS >25% rock fragments + quartz relatively fragile - less chemical weathering &/or transport since lithic fragments are Other minerals commonly found: [rel. common] muscovite, biotite, amphibole, pyroxene, olivine [rare] Also: CLAY [if lots -- a wacke] zircon, garnet, epidote, chlorite, magnetite Fossils Siltstone quartz, clay Mudstone small grain size --- long distance of transport FACTORS THAT CONTROL COMPOSITION --SOURCE ROCK CLIMATE controls amount of weathering intense chemical weathering can destroy susceptible grains TRANSPORT as increase Distance lose susceptible grains and reduce grain size DEPOSITION influences amount fossils, etc. DIAGENESIS amount chemical alteration RELATION TO PLATE TECTONICS -Recall composition of igneous rocks tied to plate tectonic margin -ANDESITE ----- CONVERGENT BASALT & GABBRO ----- DIVERGENT SO SEDIMENTARY ROCKS? Indirect relationship. Seek to I.D. source rock Rock Source Lithic SS Arkosic SS Quartz SS Siltstone, MS chemical Tectonic Margin commonly andesite subduction commonly granite, conti-conti convergent & metamorphic rocks clues destroyed by commonly stable & transport Chemical Sedimentary Rocks Index) (Return to Page 7 Course Notes Features in common w/clastic rocks: - form via the sedimentary cycle Differences from clastic rocks: - transported as IONS in solution - precipitated ---- not deposited So is grain size, sorting or rounding important? Chemical Sedimentary Rocks features in common w/clastic rocks: form via sedimentary cycle Differences from clastic rocks: transported as IONS in solution, precipitated -- not deposited So is grain size, sorting or rounding important? Chemical Sed rocks very susceptible to chemical alteration during diagenesis - esp. recrystallization Chemical sedimentary rocks form by - organic reactions from activities of plants/animals w/water or inorganic reactions within the water, for ex., evaporations Classified by composition - generally, each is only one mineral LIMESTONE: (very common) how ID?: made of calcite --- soft, fizzes w/HCl different textures: - bioclastic = lots fossils, incl. COQUINA= porous variety, shells broken - oolitic: has ooids - crystalline: “plain” DOLOSTONE: how ID? made of dolomite -- soft, doesn't fizz COAL = compressed plant material how ID? made of carbon --- light, black, shiny Evaporites - both have crystalline texture ROCK GYPSUM: very soft, ours are porous ROCK SALT: taste CHERT = fine grained silica how ID? hard, opaque, white-red-black Relation to tectonic environment? Only very indirectly. Mostly record the environment and vary with climate. Generally stable tectonic environments Features of Sedimentary Rocks Index) Primary Sedimentary Structures: form before burial - (Return to Stratification = bedding = layering Parallel Strata - common in lakes and ocean sediments or cross beds, and ripple marks - record current direction Graded Beds - represent underwater landslide deposit Cross Strata Mud cracks - climate information Raindrop Impressions Clast Imbrications - record current direction Sole Mark - record current direction Trace Fossils - records movement or other features of creatures Secondary Sedimentary Structures Concretions & Geodes: well cemented areas of rock, any shape Stylolites: dissolution scars Color DEPOSITIONAL ENVIRONMENTS: ID using rock types & primary sedimentary structures Terrestrial: glacial fluvial: in channel, cgl, ss, Xbeds; in floodplain: siltstone, MS Page 8 delta: ss- Course Notes silt-ms +/- coal (oil) alluvial fan: cgl desert: Q ss, xbeds (dunes) playa lake: evaporites, ms w/mudcracks lacustrine: parallel bedding; ms, silt in center; cgl, ss on shore landslide: breccia over small area (generally) swamp, bog: coal Shallow Marine: beach & barrier bar: cgl, Q ss; ripple marks, xbeds, trace fossils shelf reef: bioclastic LS lagoon: crystalline LS or MS marine evaporite basin Continental slope: mostly erosion Continental rise: submarine fans, turbidites, graded beds Deep marine: clay, volcanic ash, dropstones = abyssal plain: parallel beds, MS, microfossils METAMORPHIC ROCKS: important because? economic: gems, building stone oldest rocks preserved common in mountains, records their locations protolith = original rock CONTROLLING FACTORS IN METAMORPHISM (Agents of Change) (Return to Index) TEMPERATURE T > Sedimentary Diagenesis (200ºC) T < Melting (750ºC), Igneous As T • some minerals become unstable --- rearrange into new ones • minerals grow bigger crystals • rock bends like plastic Heat Source • Earth's internal heat ---- natural radioactive decay via DEEP BURIAL (under mountains) INTRUSION • Locally: friction generated along faults PRESSURE Lithostatic or Uniform or Confining Pressure decrease Size increase Density Directed or Differential Pressure or MAGMA -- mass and shape same shape change --- pattern = Foliation, minerals aligned Shear Pressure grinds rock up; occurs along faults; develops cataclastic texture Pressure Source • DEEP BURIAL (>1000 m deep) Effects on a common rock -- Mudstone Conditions Low T, Low directed P (low grade) Foliation Slatey Cleavage Intermed. P & T (low-intermediate grade) Phyllitic Texture new minerals? ----(just aligned) small micas high T & P Schistose Texture or micas (intermediate to high grade) very high T & P (high grade) large crystals, various minerals incl. amphibole, Gneissic Texture Feldspar, Amphibole Chemically Active Fluids --- Water --- faster changes ----- larger crystals & unique minerals source: sedimentary rock, some minerals, volatiles from igneous intrusions Other Factors Page 9 Course Notes Composition of Protolith (=rock start with) Limestone ----- Marble Conglomerate --- Metaconglomerate Time more time larger crystal size ----------------------------------------------------Metamorphic Rock I.D. --Texture Composition Name (protolith) Nonfoliated calcite Marble (limestone) Nonfoliated quartz Quartzite (sandstone) Nonfoliated carbon Coal (coal) Nonfoliated silicates Hornfels (various fine grained rocks) Slatey Cleavage Slate Phyllitic Texture Phyllite Schistose Texture Mica, or Amphibole or Serpentine Schist Gneissic Texture Feldspar, + Amphibole Gneiss TYPES OF METAMORPHISM Contact: T up, fluids (hydrothermal) nonfoliated, ores (sulfides, oxides) Regional: T up, P up foliated rocks Dynamic: P up cataclastic rocks = mylonite along faults, occurs at all tectonic boundaries METAMORPHIC FACIES: blueschist, eclogite, granulite, amphibolite, greenschist, hornfels Metamorphic rocks @ subduction boundaries: blueschist, amphibolite-granulite, contact meta @ continent-continent boundaries: regional meta @ divergent: contact meta @ transform: dynamic meta only Weather Air pressure: increases as elevation lowers so more air at mtn tops or in valleys? As T increases, air pressure decreases ozone in upper atm made there, CFCs etc interfere with that What is Earth's Air made of? atmosphere composition: N2 78%, O2 21%, other stuff: CO2 , CH4 = greenhouse gases, O3 = ozone, smog = particulates, O3 , Hg, SOx, HF, NOx, others water: 0.3 (desert) to 4% (rain forest) relative humidity: meas. water/amt water that air can hold absolute humidity: mass of water in a volume of air dewpoint: T at which air becomes saturated Where did those gases come from? comets & METEORS supply N2 , CO2 , H2O, etc (based on H isotopes), recycles by volcanoes remember fumaroles? oceans form & CO2 is dissolved in it --- later becomes carbonates Page 10 Course Notes Life starts to modify the air composition 3800 m.y. or so adds CH4 , takes out CH4 , then photosynthesis by some bacteria - removes CO2 , puts in O2 puts CO2 in coal (from trees & etc) & other fossil fuels about 1000 m.y. multicellular animals show up & take out some O2 , put some CO2 Other gases From Burning SOx: colorless, odorless, damages lungs + water = acid rain: kills plants, fish, leaces HM & adds to water CO: colorless, odorless, deadly CO2: colorless, odorless, greenhouse gas HF (from coal): powerful acid NOx: brownish, irritates eye-nose-throat, damages plants, 25% from coal +O2 = ozone (O3) Ozone: kills plants, damages eyes, respiration *Particulates: lots of diff kinds, incl HM: Pb, As, U, Hg.... Hg: coal is largest source, hard to clean up - liquid/gas, brain damage, 60000 children/year Deposit toxins in lungs, tied to lung diseases incl asthma: 100s of 1000s attacks chronic bronchitis up 400%; increase chance of dying from asthma, emphysema, and heart disease coal: responsible for 10-20% of hospital emissions decrease visibility, Big Bend Park, lost 80% of visibility Size of particulates PM2.5 & smaller: too small for rain or gravity, goes worldwide, weighs least, but lots!, does most damage PM over 2.5: mostly natural, rain takes out, falls out, weighs most Kills >> 7 million a year (WHO) ex., 37% higher risk breast cancer if live in smoggy area >deaths from murders & car accident & AIDS everyone's life a few years shorter travel the globe - most not removed by rain What about scrubbers etc? pollution credits remove by weight <PM 2.5um worst size may only remove one pollutant too late for some areas Where shall we move? What color should the sky be? Geologic Time: Part of any Geologic Study = History of the Earth • framework for current situation • helps predict future & location of resources world's geologic history (Return to Index) RELATIVE AGE DATING = determine sequence of events, oldest to youngest Sedimentary Rocks most useful - are layered - cover the surface - can contain fossils Basic Rules • most sediments deposited in horizontal layers need to be sure layers not flipped over Page 11 • relate study area to Course Notes use Primary Sedimentary Structures: Graded beds, ripple marks, cross beds, in place Plant fossils If not flipped over --• Oldest at the bottom • Whatever (fault, dike, etc.) cuts across the layers is younger than the layers it cuts GAPS IN THE GEOLOGIC RECORD -- due to changes in environment - sediment may not be deposited for a time and/or - sediment may be eroded Result = UNCONFORMITY Angular Unconformity flat layers over folded layers Disconformity flat layers over flat layers Nonconformity flat layers over metamorphic or igneous rocks Relative Age Dating + Absolute Age Dating = Geologic Time Scale -- used worldwide The Solar System planets: similar early histories terrestrial: density >4g/cc; rock & iron; moons </= 2 jovian: density <2 g/cc; gas/ice + rock; moons = lots; rings "dwarf planets" other objects Mercury: elliptical orbit, small, dense --- mostly core; T: varies 450C to -184C ATM: none; surface: heavily cratered --- preserves events of early history, 1 volcano magnetic field - despite lack of volcanic & slow rotation - partly molten core Venus: retrograde rotation, close to Earth in size & history, no magnetic field ATM: CO2 (N, SO2); 100x earth's; 4 thick cloud layers T: c 500C no moons wrinkled mountain formations indicate compression and wrinkling: total relief 13km; tectonic activity? surface: scattered impact craters, volcanic regions, shield volcanoes, smooth lava flows History of Venus: complicated history, still poorly understood. very similar to Earth in mass, size, composition, density, but no magnetic field = core solid? solar wind interacts directly w/atm. --- bow shock & long ion tail CO2 produced during outgassing remained in atm. (on Earth, dissolved in water) any water present on surface rapidly evaporated - feedback through enhancement of greenhouse effect. Heat transport from core mainly through magma flows close to the surface (pancake domes, etc) The Geology of Mars: giant volcanoes, valleys, impact craters, reddish deserts of broken rock, probably smashed by meteorite impacts T: 27C to -100C ATM: CO2 , thin polar caps: frozen water, dry ice (CO2 ) Seasons 1/2 earth size lowest density of terrestrial - small Fe core >2 moons = captured asteroids northern hemisphere: volcanoes, some active? Olympus Mons 27km tall, ,100 m.y. thick, rigid crust, no horizontal motion Erosion: Eolian, ventifacts, dunes andesite composition? possible subduction? or sedimentary rock? The Geology of Mars: northern lowlands = free of craters, probably resurfaced a few billion yrs ago no magnetic record in these rocks; possibly once filled with water Southern highlands: heavily cratered, probably 2-3 billion yrs old. Rocks retain magnetism Evidence of water on Mars: minerals (hematite, gypsum), shorelines, channels, conglomerate, rounded boulders Life? meteorite = ultramafic igneous rock 3,600 m.y., ID as from Mars = noble gas concentration & rock type carbonate minerals inside meteorite bacteria body fossil? or inorganic minerals? + complex organic molecules w/lighter C isotopes + magnetite Asteroids = fragments of rock, iron Belt - source most meteors, craters Comets = dusty icy chunks Mostly Kuiper Belt & Oort cloud beyond Pluto both supply water + amino acids + heat to early Earth Irons; Stony: achondrite, chondrite: plagioclase & pyroxene; stoney-iron: igneous, core/mantle boundary, olivine & metal Kinetic Energy - potential energy & heat; shattercone Tektites; shock lamellae; other evidence: stishovite & coesite, iridium, osmium; impact breccia; craters on earth - Page 12 Course Notes rare The History of Jupiter: formed from cold gas in the outer solar nebula, where ices were able to condense rapid growth; soon can trap gas directly through gravity; heavy materials sink to the center; in mantle, hydrogen becomes metallic (very good electrical conductor); rapid rotation -- strong magnetic field; rapid rotation + large size -- belt-zone cloud pattern Jupiter: largest, releases 2X energy than receives; atm: H, He, ammonia, methane... stormy, winds to 330mph Ring system: continually sucked in to planet & replaced, dust from meteorite impacts onto inner moons trapped to form ring. Moons: Io, volcanic, >100 active volcanoes, erupt S, SO2 , basalt, cause Tidal Forces, too small to hold atm Europa: ice crust, fractured over water layer "ocean", ice fissure eruptions, Life? Ganymede: impact craters, some surface renewal, very large moon Callisto: no renewal, shrank?, also very large Saturn: seasons, releases E, magnetic field, rings >1000; low density & oblate - small core smaller moons: Hyperion too small to pull itself into spherical shape Titan: thick atm, 10x Earth's thickness; mostly N, ethane, acetylene, ethylene, H cyanide, thick opaque layer: surface: ice continents (T -180C), oceans?? of ethane & methane; Mtns discovered on Titan dunes: on Titan, 100-150m high, moderate sand supply + seasonally variable winds; sand = fluvial? has channels & rounded boulders or hydrocarbon solids from air Uranus: extreme tilt of axis, seasons, magnetic field reversity?, T-200C; rings Moons: Miranda - evidence of mantle circulation?; Oberon - lots of craters Neptune: stormy, winds to 1400 km/h, H-He-methane, T-212C; moon: Triton, only one orbiting backwards; rings Dwarf Planets: Pluto - seasons, growing ice caps, atm: 2 layers, N, CO, methane, elliptical orbit, not same plane Charon - very different, has water ice Captured Kuiper belt objects? Escaped Neptunian moons? features explained by: solar nebula theory, modified by impacts & by evolution - terrestrial influenced by size & dist solar nebula theory explains: terrestrial vs jovian compositions (refractory vs nonrefractory elements), planet sizes, orbit & rotation counterclockwise & in the same plane PRECAMBRIAN: most of geologic time, difficult to study: fossils rare, rocks altered-eroded-or buried, <20% exposed rocks Why study the Precambrian? Learn past history: sets stage: organization (crust, mantle, core) Life, oceans, atm form, also Precambrian; has resources (diamonds, Au, Cr…) (Return to Index) Hadean: 4567 to 4000 m.y.; planet formed by accretion, Fe melt 1st & sink to center; volatiles escape to surface >4.5 G.yr. Earth probably hit by Mars-size object; blasts off part of Earth (mainly mantle) + impactor frags = moon; Earth probably loses volatiles; consequences = moon steadies Earth, slows Earth, moon closer then more data from Mercury & our Moon - preserves early history of terrestrial planets, What was happening? high rate of impacts till 3.9-3.8Gyr, in pulses and from meteorites & physics: Meteorites: iron, silicates, volatiles, amino acids; Comets: water, amino acids Minerals: oldest on Earth 4.3-4.4 G.yr. Zircons: very resistant, trap U & Th, show crust existed & water Hadean Earth: 1st crust = ultramafic lava & basalt HIGH HEAT FLOW: Due to: heat from formation, impacts: cataclysms in Hadean & Early Archean & more radioactivity; lava indicates T = 1600ºC One Result --- More Volcanoes • release heat to space --- earth cools • release volatiles = H2 O, CO2 , N2 , H2 , CO....--- forms ammonia, methane --- missing? free oxygen, ozone layer, was ANOXIC Page 13 Course Notes = the Achaean atmosphere from volcanic outgassing & meteors & comets DATA: detrital pyrites & uraninites - not rusted even though exposed to air - so no O2 in air AND -- Oceans zircons -- liquid water @ surface 4.4 G.yr. • ocean facies rocks by 3.8 b.y. deposited in deep water: Turbidites: underwater landslide deposits. Chert: deep water chemical sediment. -- stable oxy 16O/18O ratio indicates T = 55-100ºC Pillow Lava: underwater lava eruptions Oldest rock = 4.28 G.yr., NE side Hudson's Bay, Canada, is an amphibolite MISSING/RARE IN ACHAEAN • shallow marine rocks, ophiolites – oldest 2.5 b.y. • terrestrial sedimentary rocks --- those environments rare tectonics: small, fast plates; no large conti, lots volc, accumulate CO2 GREENSTONE BELTS: ultramafic lava --- basalt --- deep marine seds; folded & intruded (granite) granulite (granite-gneiss) - protolith unknown, most common Archean rock Australia: proto-continents & greenstones; form small continent blocks -- that start to combine into larger ones Archean life: amino acids (heat) -- polypeptide (polymers) drying -- microspheres -- link molecules -- RNA Why did building blocks form? Need area w/high concentrations of chemicals + source of energy black smokers = hydrothermal vents in the oceans, H2S, concentrate on minerals like pyrite, high T tidal (or lacustrine) pools - concentrate with evaporation, solar (UV) energy Evidence for Archean Life: Stromatolites: oldest 3.4-3.5 b.y. are carbonate layers trapped by bacteria Graphite: oldest 3.85 - 3.7 G.yr. C ratios --- organic source = carbonized bacteria Body Fossils: oldest 3.5 G.yr., carbonaceous cell walls, size 1-4 microns, preserved parallel to layers, some in apparent cell division Chemical Fossils complex organic molecules - 2,800 m.y. C-isotope depleted kerogen molecules - methane trapped in quartz, >3500 m.y., probably formed by methanogenic bacteria that lived underground - S-depleted pyrite, maybe from sulfate reducing microbes PROTEROZOIC large continents form; 51-79% by 1800 my evidence of continents: terrestrial rocks, shallow marine, orogenic events (plutons & meta rx), radiometric dates from zircons Sandia granite, Red Bluff Granite & Thunderbird Fm, intrude each other, caldera formation How build continents? --- Intrusions, thicken continent crust Formation of Laurentia, early-middle Ptz = North America + Greenland + bits of Europe Formation of supercontinents --- orogenic events, Grenville Orogeny; Maine to VanHorn---paleomag data; best known = Rodinia, rifts apart 800-700Ma southern boundary is active margin for ~800Ma, similar to Indonesia; multiple collisions of islands, arcs, and finally a continent Castner Formation 1260 +/-20Ma to 1400Ma, stromatolites, mudcracks; Lanoria Quartzite, xbeds shallow marine & terrestrial rocks: quartzite-marble-hornfels, protolith: ss, limestone, shale; 60% of known Ptz rocks Evidence of continents: terrestrial rocks: conglomerate, glacial rocks Glaciations: deposits: breccias=tillites, dropstones, varves Early Ptz glaciation: Finland, So. Africa, India Most extensive ever: all continents except Antarctica -- Snowball Earth (most) oceans frozen too, >2 major episodes: Sturtian & later Varangian; breccias asso w/LS, DS, evaporites, red beds possible explanation Global Ice Climate, "snowball", drop in CO2 --- spread of photosythesizing cyanobacteria---increased continents--more weathering; drop in methane -- bacteria; additional H sulfide --- volcanic activity Page 14 Course Notes Changes to the Air Archean: anoxic, reducing, Oxygen 0.2% of air, lots CO2 , methane; Proterozoic: oxidizing, 2% of air, ozone shield forms, less CO2 , methane Banded iron formation abundant 2.3-2.2GY, oxygen sink, ocean deposit Proterozoic Life acritarchs (2Gy last till Paleozoic=base of ocean food chain; single cell, but Eukaryotes; still have prokaryotes Eukaryote Cell: preservable differences: size, nuclear membrane, chemicals (biomarkers), faster evolution 1st evidence eukaryotes 2700 my Next big step: multicellular life - 1st probably clusters of single cells, non-specialized then true multicellular - have specialized cells. Oldest = 2.2-2.1 Gy, are multicellular algae, after ice age multicellular animals developed later in the Proterozoic 1st multicellular animals = all soft parts multicellular Animals = ?possible trace fossils: VanHorn, at least 1.2Gy old ?jellyfish? impression, Grand Canyon 1.1-1.3 Gy old if supported by later discoveries = oldest known metazoans 1000 m.y. ago, body fossils (impressions) + trace fossils + disruption of the strata. The trace fossils become more complex & variable as they get younger. 1300m.y. old seds - no burrows/trace fossils Ediacara Fauna: 680Ma into Cambrian, Vendobionts or ancestors & relatives of Phanerozoic organisms become more complex with time, increase in diversity tied to the end of .....? and an increase in what gas? include first hard parts - both phosphate & calcite types = worm tubes, hyolithids, mollusks, sponges Early Paleozoic Life Cambrian Explosion: Cambrian - high sea level - lots shallow marine environment, lower boundary = major increase in diversity Small Shelly Fauna = over 40 different kinds, various phyla; different compositions appearance of hard parts: excreting excess minerals, 1st shells = aggregates; variety skeletons: internal/external; Ca phosphate, CaCo3, silica hard parts used for? Main Explosion or radiation: 533-525Ma Arthropod: Trilobites (guide fossils), others seafloor, detritus eaters Brachiopods (Cambrian to now) attached, lived on seafloor, suspension-feeders Archaeocyathids Cambrian only built small reefs Chordate: Yunnanozoon lividum Haikouella lanceolota from Chengjiang swam Chordate: conodont animal, bulbous head, animal swam mobile, lived on Burgess Shale = underwater landslide deposit, fast burial preserves soft parts; mostly seafloor animals, fewer swimmers caught remarkable preservation= lagerstatten; also one in Chengjiang, China (older) Hallucigenia, Wiwaxia, Opabinia; all of these are less than 3" long Burgess Shale Fauna: all major invertebrate phyla but 1 present; all major body plans appear + lots of experiments Anomalocaris, Santacaris, Opabinia, Waptia, sponges, Pikaia, Hyolithids, Hallucigenia Cause of explosion? favorable climate/environment: Oxygen level, sea level, phosphorus, warm temperatures critical level of biocomplexity: hard parts, diversity Triggers: eyes, predation, substrate changes Diffraction gratings - indicate color Ordovician: second major jump in diversity; one new phylum=Bryozoa; built large reefs: corals & stromatoporoid sponges Chordate: fish-ostracoderms, jawless, detritus eater (except perhaps the largest) Early Paleozoic Tectonics 6 major continents, several near equator, high sea level, maps based on: paleomagnetism, environment of deposition, orogenic events Cambrian: Sauk sea, Bliss Sandstone, glauconitic & hematitic quartz sandstone: shallow marine, tidal flats w/small pools & channels Sauk/Tippecanoe sequence: highest sea level of Paleozoic, 100-225m higher than now, caused by rapid seafloor Page 15 Course Notes spreading Ordovician: El Paso Group/Montoya Group, Queenston Delta, folds, thrust/reverse faults, Taconic Orogeny End Ordovician Mass Extinction: main victims=corals, sponges; also hard hit: trilobites, nautiloids, brachiopods, crinoids faunas from high lat migrate to lower lat. lower rate LS depos. cause: climate change --- cooler, due to sea level fall & glaciation Middle Paleozoic: Silurian & Devonian marine life: rediversification after extinction, luxuriant reefs, bigger than Ordovician reefs, framework builders same trio as before arthropod: eurypterid, Ord-Perm; greatest diversity Sil & Dev; freshwater, brackish & marine Devonian called the Age of Fish First jaws = acathodians; small, 1st in nonmarine, then marine; fins supported by spines, 1st w/paired fins & Scales new lifestyles & can open mouth wider, adaptive radiation of fish Placoderms: teeth & armor, latest Sil/Dev - Carboniferous, most predators largest 12m, some freshwater cartilagenous fish: class chondrichthyes, mid-Dev to now Bony fish: ray-fin fish, modest success in Dev, dominant in Mz & Cz; asymmetric tails, non-overlapping, diamond shaped scales lobe-fin fish, attach to body with fleshy shaft, greatest success in Dev, include lungfish, lungs & Limps developed for life in freshwater, include ancestors of amphibians Invasion of Land engineering for life on land: support, wind, reproduction, drying out; only algae & simple plants near water till midPz ancestors = green algae; 1st upright, no roots, no leaves, etc; non-vascular, spore-bearing; moss-like appear early Ord; Late Ord rigid stems midSil = 1st vascular plants, simple tube system, still spore-bearing; great adaptive radiation in early Dev leaves evolve in several lines of plants in Dev Trees appear, spore-bearing, including Lycopods = coals Next development = seeds, 1st in Dev, allow plants to expand range, forests appear --- meandering rivers appear--CO2 level drops change in plants in Dev Animals invade Land: Latest Sil; 1st = arthropods: millipedes, centipodes, scorpions, flightless insects, spiders, trigonotarbids.. Latest Dev: vertebrates on land, limbs probably develop for shallow water Ichthyostega - a Labrynthodont Amphibian, lots fossils in Old Red SS (elsewhere), reached over 3 feet long Labrythodonts (Dev - early Cretaceous) fossil larvae have gills End Devonian mass extinction (2nd of Big 5) hardest hit: tropical reef community, esp., coral-sponge, acritarchs, placoderms; polar communities - unaffected; large drop in Brach, ammonoids, gastropods, trilobites; little change in vascular plants cause? global cooling --- related to spread of land plants & glaciers. (change in ocean circ) spread of euxinic bottom conditions (reducing O2) +/- impacts?? but happened over 20 m.y. Acadian & Caldedonian - closure of Iapetus Sea; suture Laurentia & Baltica together = Laurasia reefs & evaporites in Williston Basin, Canada; Antler Orogeny = accrete volcanic terrane; Acadian orogeny Catskill Delta; cratonic sequence = Kaskaskia, Percha shale in EP area Late Paleozoic Marine Life greatest diversity of crinoids, fusilinid foraminifera Protorezoa; reef builders = Brachiopods; fish: placoderms gone, give way to more mobile forms On Land: Carboniferous - spore bearing plants, sphenopsids: Calamites, Lycopsids: Lepidodendron, Sigillaria Gymnosperms - seeds in cones, diversify & spread as climate dries Glossopteris - seasonal rings, coal former, seed-fern Phylum: Arthropoda, insects discover flight, largest 0.5m wingspan Phylum Chordate: amphibians from Late Pz of Las Cruces, NM Pennsylvanian: reptiles appear - better jaws, faster, more agile; oldest reptiles = small, minor diffs from amphibians = Protorothyrids Page 16 Course Notes Pelycosaurs (Penn-Perm) later reptiles: stronger jaws, slicing blade like teeth Therapsids: mammal-like reptiles (mid-Perm to Triassic), legs vertical, flexible, under body; jaws more complex & powerful, *teeth differentiated fur - warm-blooded?, some in polar areas; descendents of pelycosaurs, ancestors of mammals Late Paleozoic Tectonics Mississippian: Absaroka/Kaskaskia sequence = Las Cruces Fm Tillites/glaciated surfaces Glossopteris Pennsylvanian: assemble Pangea - tectonic activity + glacial advance/retreat - lots small sea level rise & fall --cyclothems; coals: Lycopsids, sphenopsids Hercynian, Alleghenian, Ouachita, Ancestral Rockies, Maurintinide Ancestral Rockies: deformation in the craton Permian: eroding uplifts & deserts; Capitan Reef = rim Delaware basin, evaporites when sea level low Ural orogeny; Absaroka restricted; continent interior dry; complex topography + steep climatic gradient = high provinciality Late Pz climate changes: glaciation: variation in greenhouse gases, spread plants, drop CO2, drop T---- ice age drying trend: large continent, dunes, evaporites; Pre-Pangea = spore-bearing, amphibians; Pangea = seedbearing, reptiles Terminal Permian extinction main victims: terrestrial vertebrates; in marine: Xfusilinids, Xcorals, Xtrilobites; heavy losses: ammonoids, brach, bryozoa, others; no reefs built for next 12m years moderate losses: gastropod & pelecypods; peat-forming plants go extinct (fewer coals) occurred in several pulses, not synchronous world-wide, though sudden heaviest losses in low-latitude --- cooling cause: drop in sea level + Siberian Flood Basalts Early Mesozoic Marine Life = descendents of extinction survivors, diversify into new lifestyles Chordate, Reptile: Placoderms, Triassic only, ate shells; Nothosaurs, Triassic only, ancestors to many others Plesiosaurs - mid Triassic - K Ichthyosaurs (Triassic - K) fully marine, live birth, over 80 different kinds, largest over 15 m long Triassic Terrestrial Fauna Dominant: Therapsid reptiles; other reptiles present: Thecodonts, rhyncosaurs, dinosaurs, crocodiles; Plants: seed-ferns - Dicrodium Gymnosperms dominate Early Triassic flora, Dicrodium seed ferns important (gymnosperms) New to the planet in the Triassic: turtles, head & tail not fully retractable; mammals - almost all were small, many nocturnal End Triassic Mass Extinction 20% drop: marine families; on land: most dominant reptiles, plants - gymnosperms replace lowland plants (Dicrodium) Cause? climate change - more arid? 210 +/-4Ma, quebec, 100km impact crater coincides with one pulse of extinction Dinosaurs Thecodont (ancestor) Early dinosaur: Coelophysis, appear early Triassic, resemble Thecodont, legs directly under body, agile, fast; skulls different, teeth more developed, bipedal Theropod: all carnivores & bipedal, from small - Coelophysis, Protoarcheopteryx, to huge: Tyrannosaurus, Gigantosaurus, Carcharodontosaurus Sauropod: quadropedal herbivores, include largest land animals ever Pachycephalosaur: Thicked skull bones, for mating?; Ankylosaur, most heavily armored Stegosauria: small brain (~3oz) Hadrosaur, also called "duck-bill dinosaurs" air chambers diff for diff species for young, males, and females; evidence hadrosaurs took care of young in large nesting colonies Ceratopsians: huge head w/bony frill & horns; traveled in herds Order Pterosaur (reptiles but not dinosaur): brain size increased, warm-blooded? fur; largest ever = Quetzalcoatlus, 65kg, 12 meter wingspan Page 17 Course Notes Class Aves (birds) Definitely by Jurassic, maybe earlier; Archaeopteryx: no breastbone, skeleton very similar to Compsognathus (small theropod), flight feathers Were dinosaurs warm or cold-blooded? Evidence comes from: brain/body ratio, predator/prey ration, holes in bones, insulating feathers, fast growth, chewing math model - incorporating Mz climate warmer than today Early Mesozoic (Triassic & Jurassic) rifting: thick seds - Newark Grp, basalt - Palisades Sill, normal faults climate: low T gradient, generally arid: evaporites, dunes, red beds Jurassic: northern Atlantic widens & lengthens; southern Atlantic starts over 150,000 km2 of sand dunes; Navajo SS, Wingate SS, Dakota SS, Louann Salt, Smackover LS; Jurassic Nevadan Orogeny, Sierra Nevada Granite, Morrison FM Late Mesozoic: Cretaceous, named for chalk = plankton debris high sea level + warm climate Life = mix of modern & extinct config continents moving toward modern Carnivores: Mollusk Cephalopods, some unusual coils Chordate: Bony fish: Teleost fish, largest = Xiphactinus, c.5meters reptile: Mosasaur, huge up to 15 meters long; plesiosaurs reach over 10 m long; ichthyosaur & marine crocs rare Terrestrial Flora mid -K: angiosperms, "flowering"; 1st ones, no obvious flowers *** enclosed seeds; late-K: surpass gymnosperms, no grasses co-evolution: flowers & insects + fast cycle - seed to plant Terrestrial Fauna pteranodons & birds; sauropods decline, hadrosaurs, ceratopsians increase dinosaur beach: tracks in EP area: ankylosaurs, carnivores, others recent discovery in China: mammal that ate dinosaurs, Repenomamus robustus (4-6kg) had small dino skeleton inside; most mammals small, nocturnal, many insectivores by end K: representatives of monotreme, marsupial, placental Cretaceous paleogeography climate: warm, equable, oxygen isotopes, reef extent, black shales sea level - very high: evaporites, reefs, lots plankton = oil Cordillera orogeny: subduction of Farallon Nevadan (J-K): Franciscan Grp: melange, blueschist; Great Valley Grp: submarine fan + lithic sandstones; Sierra Nevada Granite: batholiths; accreted terranes, ophiolites K interior seaway: <400m deep, sank due to load from mtns - black shale; Gulf coast: carbonates then coals; east: isostatic uplift - passive margin subduction angle shallows: Sevier orogeny (late J-K) folds, thrust faults during K: igneous activity migrates east then shuts off as subduction angle shallows Laramide orogeny (K-Eo) folds, thrust faults, igneous shuts off; in EP: anapra sandstone, deformation K-T extinction: gone forever: reef builders, dinosaurs, swimming reptiles, flying reptiles, most cephalopods, many plankton survivors: many molluscs, plants, birds, mammals, reptiles: crocodiles, turtles, snakes; amphibians: frogs.... Theories: climate cooling Evidence: tropical hardest hit, stable isotopes of C & O; some cold adapted spread Theory: disease Theory: volcanic activity Evidence: Deccan Traps, India, gas bubbles in amber Theory: impact Evidence: high Ir & osmium, Chicxulub structure w/breccia, melted rocks; tsunami deposits, tektites, microdiamonds, shocked quartz, C sperules = soot layer Summary: Cenozoic era Page 18 Course Notes rapid diversification of K-T survivors; insects, frogs, birds, rodents, snakes; grasses, herbs; swimming mammals; Alps, Himalayas, Rockies, Pyrenees, Laramide, Atlas, Zagros, Andes; cooling & drying rocks & fossils better preserved than any other time in geol history Sharks, up to bus size early whales: descendents of terrestrial mammals, appeared Eocene, includes Basilosaurus, usually 50ft long, some 80ft Angiosperms dominate, new varieties appear, incl grasses (K-Paleocene) colonize rapidly (budding), important Oligo-Miocene Paleocene Terrestrial Fauna: first bat, largest mammalian predator = 2m to shoulder, small hooves; mammals = generalized; reptiles=snakes, turtles, crocidiles; amphibians=frogs (true by Eo), salamanders; birds Eocene: mammal variety & size increases: creodont, pantodont, condylarth, brontothere, uintathere, largest land mammal ever= long-neck rhinoceras, 18ft to shoulder Diatyrma Order Carnivora: saber-tooth cat, bear like dogs, wolf-like animals Paleogene paleogeography & climate change Pacific outlet blocked by Bering Land Bridge throughout Paleogene, rift between Greenland & Scandanavia widens @end K: @south pole but warmed by ocean current; Australia rifts away, moves North, cold current encircles Antarctica, 1st sea ice near end Eocene, cold water sinks, moves N as deep sea current extinctions of sea floor life esp forams; Eocene/Oligocene boundary: Antarctica starts to grow glaciers Europe: microplates; Italy collides with Europe --- Alps Africa: moves north, closing Tethys --- Atlas; Libya & Egypt = passive margins -- thick limestones w/forams, sharks, whales, oil; covered by clastic rocks w/tree & mammal fossils India: closes ocean, collides with Asia - Eocene --- Himalayas 55-45m.y. Laramide continues: volcanoes & fold/thrust faults, fold & thrust faults only --- mountains; low-angle subduction, fast convergence +/- young ocean crust Laramide features: Cristo Rey, Lewis Overthrust, Olympic Mtns sediments off of Laramide: Wasatch Fm, Green River Fm, anxious to mine it for oil Lots volcanic activity - some asso w/hot spots Eocene Paleogeography: California under water, San Andreas starts; EP Santa Fe Grp Gulf Coast: Tejas Sea, oil, then buried by Mississippi river seds - subsidence East Coast: isostatic rebound & erosion Neogene Life whales expand, incl dolphins dryer, cooler, more seasonal: increase grasslands, decrease forests; animals evolve to take advantage of new food source: songbirds, increase rodents, frogs, insects, predators - incl poisonous snakes variety: to adapt to life in grasslands; some animals increase in size: speed, easier to digest poor food & maintain T mammoth: grazer; mastodon: browser: cats - many predators designed to attack in open country; scavengers: condor Early Cenozoic (Paleogene) Primates = binoc vision, grasping hands, complex social Prosimians then Arthropoids like Aegyptopithecus: arboreal, relatively large brain/body ratio Late Cenozoic (Neogene): first Hominids ~6-7Ma, are mixes of primitive: small brain in Sahelanthropus & derived: reduced canines, bipedal compare brow ridges, jaws, forehead development Extinction of Megafauna climate change? isotopes, glaciers; ?Overkill hypothesis: not 1st climate change, timing matches man, not always climate Neogene Tectonics The American west: widespread tectonics & igneous activity, climate changes What are the 3 causes of mountains? what are the 3 causes of volcanoes? Which uplifts are rainshadows? Cascade range: subduction of Farallon remnant Columbia plateau --- Snake River plain --- Yellowstone Miocene --- Plio-Pleistocene ---- Recent Page 19 Course Notes California: San Andreas Fault, begins Eocene, over 300 km of offset; bend = transpression ---Transverse Range Sierra Nevada: ~4.3km uplift, rainshadow for Great Basin Basin & Range Province: extension starts Eocene, topography Miocene; normal faults, thin crust, thick conti seds, area elevated, mafic volcanics cause: "drag" asso with San Andreas, remnant of subducted Farallon, seismic tomography shows trailing edge of plate under AZ to Tx at 350-650km depth. front of plate at core-mantle boudary under western Atlantic; Appalachians isostatic uplift Gulf area, subsidence 5-10mm/yr now you know the entire history of North America Neogene World Tour East African Rift: one of RRR triple junction, Miocene+, incl Olduvai Gorge, rainshadow Sinai penninsula moves N --- Zagros orogeny India hits Asia c60Ma Caribbean: the isthmus that changed the world. Pliocene: formation of the isthmus of Panama by subduction; shifts Gulf Stream, more moisture to N, glaciers decrease #mammals in Americas: NAm placentals replace SAm marsupials; increase #marine invertebrate species evolve differently on either side of isthmus (barrier). asso w/Andean orogeny Andean orogeny: subduction, Andes, rainshadow Late Cenozoic Glaciation starts Pliocene, ends ~10,000 yrs ago, max ice reaches over 3000m thick, lots of evidence of extent current glaciers = retreating, sea level changes multiple causes: location continents, amount precip (Gulf Stream), amount CO2 - weathering - Himalayas glaciers reach as far south as Hawaii & Santa Fe, re-arrange river system Water Why study water? Floods ground subsidence water supply geologic work: shape landscape, part of sedimentary cycle hydrologic cycle energy source transport highway underground disposal Channelization: advantages: increase navigation, control floods, erosion, drain wetlands, settle boundaries disadvantages: less wildlife, lower water quality, increase floods Natural (cut bank, point bar) vs artificial channel Factors that influence amount of LOAD: climate, relief, slope, rock type How people affect load (& discharge): dams (other problems with dams), pavement, land clearing occasionally - dams fail; lots of earthen dams pavement: decreases infiltration, increases flooding (Walton slides) RIVERS DEPOSIT -- when slows down Forms what landforms ? Floodplains & terraces - drop in base level or uplift; LaMesa surface: terrace cut when Rio carved to Gulf Levees natural Artificial -- effects of? alluvial fan Delta: vary with river (discharge & load) and body of water (topography & currents) normally switch channels -- seeking higher gradients (steeper way to ocean) GROUNDWATER GROUNDWATER SYSTEM Recharge area = where water enters ground may be natural or artificial (wells, ponds) Page 20 Course Notes in humid - any permeable area in arid - mountains, alluvial fans, rivers only Groundwater moves via LAMINAR FLOW - v. slow along long curving paths Discharge area = where groundwater comes out of ground = anywhere water table intersects the ground surface natural - in arid: evapotranspiration in El Paso, use? artificial - wells or ponds to keep aquifer from collapsing & to fight saltwater intrusion arsenic can be natural or not; El Paso ave. 16ppm, EPA limit: 10ppm GROUNDWATER TRANSPORT -- dissolved ions from common rocks of area ex. Ca, Mg, K, Fe w/chlorides, sulfates, carbonate = total dissolved solids also have chlorides & sulfates (ex., salt & gypsum) El Paso - alluvium & bolson deposits Problems include: salt intrusion pollution reduced recharge overuse SELECTED NATIONAL DRINKING WATER STANDARDS CHEMICAL LIMIT (mg/L) Total dissolved solids 500 (esthetic) Chloride (Cl-) 250 Sulfate (SO ) 250 Nitrate (NO ) 10 (as N) Iron (Fe) 0.3 Manganese 0.05 Maximum. permissible Arsenic (As) 0.05 Barium (Ba) 1.0 Cadmium (Cd) 0.01 Chromium (Cr ) 0.05 Selenium (Se) 0.01 Lead (Pb) 0.05 Mercury (Hg) 0.002 Fluoride (F) 1.4-2.4 (<4) Cyanide 0.06 Endrin 0.0002 2,4-d 0.1 2,4,5-TP silvex 0.01 Phenols 0.001 Synthetic detergents 0.5 source: U.S. EPA, 1975, national interim primary drinking water regulations Ground subsidence: hazard Page 21 Course Notes sewage pollution: most common nationwide other potential sources - and animal containment systems water in Mesilla Bolson turning up with nitrates, chloride (NPR, 2015), due to cows, only top 100' +/- above where get water soln? thick plastic liners for evaporation ponds & monitoring in El Paso: have lots limestone & dolostone so lots Ca, Mg carbonate in water --- HARD WATER GROUNDWATER QUALITY MANAGEMENT in TEXAS Federal Laws + Texas Water Code: Ch. 16, 26-29, 52 primarily State funded “superfund” program Agencies: Texas Water Commission: lead agency, coordinator Texas Water Development Board Commission of Texas Texas Department of Health 17 underground water conservation district agencies Texas Water Well Drillers Board Railroad Texas Department of Agriculture ENVIRONMENTAL REGULATIONS (SOME) Resource Conservation and Recovery Act (RCRA) Clean Air Act Clean Water Act Oil Pollution Act of 1990 Safe Drinking Water Act (SDWA) Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Environmental Policy Act Toxic Substances Control Act (TSCA) Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Federal Food, Drug, and Cosmetic Act (FDCA) Asbestos Hazard Emergency Response Act of 1986 (AHERA) Emergency Planning and Community Right-to-know Act Occupational Safety and Health Act (OSHA) + more federal regulations + state and local regulations water use: El Paso & Juarez use: 190,000 acre feet/year; natural recharge <15,000 acre feet/year WATER CONSERVATION xeriscape or permaculture • SHOWER: - 40% of in-home water use & save 700 gallons/month • TOILET: - 40% of in home water use gallons/month - better than bath - flow restrictor on showerhead - reduce amount water/flush • FAUCET: - turn off while brush teeth or wash hands gallons/month • Run full loads in washing machine & dishwasher - fix leaks - can waste 200 & save 250 gallons/month - fix leaks - save ? 600 - save c.800 gallons/month more efficient appliances • Use less electricity – most power plants use a lot of water! CITY: Reuse wastewater - in golf courses potentially: cemeteries, parks, Ft. Bliss, industry Page 22 - cut 1 minute Course Notes to recharge groundwater Glacial Geology A glacier is? after treatment, as drinking water (Return to Index) How do they form? What is glacial ice? How does it form? What happens to it when it is stressed? stressed quickly? stressed slowly? How do glaciers move? Types of Glaciers: Valley Glaciers - definition of: Continental Glaciers - definition of: Zone of accumulation is? Zone of wastage is? by? Under what conditions do glaciers ADVANCE? RETREAT? How do glaciers erode? They are divided what are the effects of glacial erosion? What do glaciers deposit? (i.e.., landforms created) What landforms are created? What is an ICE AGE? what causes ice ages? how do ice ages affect sea level? land bridges? what happened when the ice age ended? streams base level? to stream valleys? to coastlines? to land elevation? How do glaciers record the past? DEFINITION OF DESERTS? to Index) Why study deserts? Can Deserts be cold? ORIGIN OF DESERTS? Atm. Circulation Rainshadow coasts (Plate Tectonics) Examples of each type Distance. from ocean (Return Cold marine LANDFORMS IN DESERTS Most created by? Alluvial Fans Other Geologic Agent? useful for? Sand moves how? Internal Drainage (bolsons) Carries what grain size? forming what? can this landform move? Loess = ? source of sand? Desert Pavement -- how form? Relation of Blowouts to oases? Desert varnish is? DESERTIFICATION Effect of Vegetation on climate? Loss of Vegetation causes? Example Causes = ? DESERT LANDFORMS * Most are shaped by water - Alluvial Fans & Bajadas sediment piles up @ base of mountains - where slope changes & rivers slow down Page 23 Course Notes - Pediments erosional surfaces of “bedrock” - Playa Lake consequence of internal drainage, water flows into valleys (Bolsons) & evaporates +/- sliding stones GEOLOGIC WORK DONE BY WIND Erosion: Deflation = removal of fine, loose particles Abrasion = sand blasting of stationary objects - ventifacts: stones eroded into angular shapes Transport: What grain sizes can wind carry? How far can it carry those particles? Particles hit each other a lot as are carried result: well rounded, unstable grains destroyed Deposition: DUNES type varies w/ wind strength & direction amount of sand, amount of moisture - coppice dune LOESS Oceanography Focus on: ocean motion, composition & rocks Ocean motion: tides, created by gravitation pull of Moon (&Sun); moon pulls side out closest to it out, Earth spins into bulge = high tide most places have 2 high/low tide cycles/day - bulge also on opposite side of globe where gravity is least Tidal currents move water & sediment back & forth perpendicular to shore if coastline has narrow bays, the currents may be dangerously fast Ocean motion: waves wind blows (distance blows = fetch), it drags water (friction) --- surface waves. Wave size is controlled by: time wind blows, fetch, wind strength, etc Waves erode & move sediment down to one half their wavelength (wave base) and in storms can reach elevations over 45m high. Erosion rates in storms may be 50X greater than "normal" Most turbulence and erosion done here, in the surf zone Since wind rarely blows exactly perpendicular to shore, waves will usually approach shore at an angle. The end of the wave closest to shore will touch bottom first and slow down. The rest of the wave is still over deeper water and keeps going faster, so waves will tend to swing around to be parallel to shore. =wave refraction wave refraction causes energy to concentrate on headlands which erode fast, and energy to disperse in bays where sediments are deposited. Over time then, shorelines become straighter and sea cliffs have great views till your house falls into the sea. wave refraction --- longshore current. The wave carries the water and the sediment up the beach at an angle, gravity carries the water back down the shore perpendicular to the shore. The net motion of the water & sediment is parallel to shore. Longshore currents build barrier bars, spits, and other landforms. They also silt up bays. If the gravity driven current (which flows along the seafloor) is concentrated by local channels - it becomes a rip current and a hazard to swimmers. Ocean motion: currents major wind belts -- surface ocean currents. ex., trade winds -- drag -- move the water + hit a continent -- turn (or the Coriolis effect due to Earth's rotation). Combo creates major current circulation systems = gyres. The Gulf Stream is part of a gyre in the Atlantic Ocean. It formed when subduction created Central America. So Plate Tectonics, because it influences the location, shape, and size of continents, has a great influence on ocean currents. Density Differences (T & salinity) --- deep currents. Water in the Arctic & Antarctic -- very cold -- sinks --- moves toward the equator. These currents formed when plate divergence rifted apart continents. Global warming may change this circulation by releasing less dense (less salty) fresh water from existing glaciers. Scientists aren't sure what effects this will have on the global climate. Climage is an exceedingly complex and interactive system, making it hard to predict its reaction to change. With 7000 million people, we have little toleration for change. Page 24 Course Notes Ocean composition dissolved elements: Cl, Na, SO4, Mg, Ca, K, other stuff; Na, Ca, K, Mg from weathering of rocks; Cl, SO4 from volcanic gases All this adds up to average of 3.5% (varies from 1-4.1%) variation caused by: temperature of water, freshwater additions & evaporation, depth, (geologic time) Lots of dissolved Fe in the water in Hadean, early Archean, late Proterozoic. When amount of oxygen increased resulted in formation of _____________ Rocks make ocean crust Beach barrier bars/spits well-sorted, well rded SS, CGL trace fossils, ripple marks, cross-beds, coquina Reef Deltas Deep-sea fans continental rise bioclastic LS SS, siltstone, MS +/- coal, oil Cgl-MS in graded beds turbidites (debris flows) deep ocean/ abyssal plain fine grain MS, LS depends on climate micro-organisms, ash, clay with occasional dropstones horizontal layers marine evaporite basin rock salt Humans & the shoreline When we build "permanent" structures along the shore - we gamble with the ocean's energy. It is only a matter of time till we lose, but we can delay the inevitable by spending money on seawalls, groins, artificial nourishment (sand added to the longshore current), or huge boulders piled against cliffs to prevent erosion. Geologic Structures Plate Tectonics Moves lithosphere (Return to Index) Deformation of rocks = any change in shape or volume of rock - shapes formed = structures Structural geologists study these shapes: how they form and what causes them. To get deformation: MOVEMENT STRESS = force/area STRAIN=deformation moving towards each other COMPRESSION shorten & thicken move apart TENSION lengthen & thin move by each other SHEAR shear elastic = recoverable strain plastic = permanent strain : Ductile = bends, Brittle = Breaks When rock strength exceeded FAILS Type of Deformation • Amount of Stress • Temperature: T rock weaker & more ductile • Confining Pressure: P rock stronger & more ductile Page 25 Course Notes Also • Time: slow stress: more ductile; fast stress: more brittle • Rock Type - minerals: quartz -- brittle; clay, calcite -- ductile - amount of water more ductile & weaker Brittle Deformation = Faults, Fractures Recognition of Faults if ACTIVE, have earthquakes for all: offset features fault breccia = mylonite; ores; canyons lakes, landslides slickensides, drag folds SEISMOLOGY Earthquakes: occur everywhere El Paso: small ones + possibility of larger Why study earthquakes? Natural causes: movement on faults: elastic rebound theory movement of magma meteorite impact Human causes: explosions injection wells load crust Record on seismograph: earthquake location: epicenter vs focus (hypocenter) travel as seismic waves = waves of elastic deformation, move in all directions from focus BODY WAVES P-WAVES: fastest, travel in solid & liquids, gas, compressional S-WAVES: shear motion, solids only SURFACE WAVES Rayleigh & Love waves: destructive, strong, slowest Location of Epicenter: distance from difference between P & S arrival times Magnitude: measure in the field, or measure amplitude & time on seismograph Damage: primary = ground motion, faulting; secondary = fire, landslides, liquefaction, tsunami, other effects Modified Mercalli Scale: rates amount damage Amount damage: depends on magnitude, distance, length, period, building strength, local geology PREDICTION: geologic record ---- average frequency precursor events EXPLORATION SEISMOLOGY: search for oil (& groundwater), define basin geometry seismic waves reflect or refract at layer boundaries - define shapes of underground structures THE EARTH'S INTERNAL STRUCTURE (Return to Index) EARTHQUAKES ---- SEISMIC WAVES ---- travel @ different. speeds ---- received at seismographs --- seismologist's model the earth SIMPLE EARTH MODEL - all the same composition --- as go down --- pressure goes up & rigidity goes up = controls on seismic wave velocity so velocity goes up however, arrival times based on simple model do not match reality best explanation --- composition varies with depth that is, the earth has layers LAYER BOUNDARIES --- Page 26 -- density goes up Course Notes 2900KM: both P & S waves change here P-wave shadow are refracted/reflected very strongly --- must be big change in composition comparatively light silicates vs iron of core S-wave shadow S-waves disappear --- so outer core must be liquid Behavior of seismic waves - define 3 very pronounced boundaries in earth separating 4 fundamentally different zones: CRUST, MANTLE, OUTER & INNER CORE THE CRUST Mohoroviçic discontinuity = crust/mantle boundary OCEANIC CRUST generally <10 km thick seismic wave velocity -- charac of basalt & gabbro CONTINENTAL CRUST very different 20 to nearly 60 km, thickest under mtns seismic wave velocity -characteristic of granite & diorite composition seismic wave velocity matches samples THE MANTLE huge part of earth control on plate movement inaccessible P-wave speed: 6-7km/s in crust; ?8 km/s in mantle P-waves faster in mantle --- means mantle > crust P-wave speed = lab test, peridotite xenoliths THE LOW-VELOCITY LAYER c. 100 km depth: ~350km boundaries not sharp plastic not a big contrast velocity drops from c.8.3 to below 8km/s remains low till infer no composition change change in rigidity --- becomes more T increased --- so rocks hot, close to melting not melted --- how know? THE LOW-VELOCITY LAYER = THE ASTHENOSPHERE key to plate tectonic theory - ? depth to top varies shallow under ocean crust: 20 km under continental crust: c. 100km THE 400 KM SEISMIC DISCONTINUITY P & S wave velocities increases sharply not compositional change density change: olivine to spinel THE 670 KM SEISMIC DISCONTINUITY wave velocity increase -- esp. P-waves observe: 10% increase in density polymorph change: of pyroxene? hard to explain but over blurry boundary of all silicates? compositional change: no, “CAT scan” (seismic tomography) **no quakes below this depth** seismic waves: density increases in mantle w/depth from 3.3 to 5.5 g/cc due to increasing pressure via phase transitions Core-Mantle transition: dynamic area, start of convection & many hot spots THE CORE average density of entire earth: 5.5g/cc 10-11 g/cc recall crust density ? 3 g/cc Page 27 to balance need area w/density = Course Notes should be common material best candidate = iron confirm w/meteorites --- many made of iron/nickel so logically, earth's core = ? outer core is liquid THE INNER CORE solid based on P-wave reflections composition = ? why outer core liquid? w/increasing depth: P increases to millions X atmP outer core (2900 to c. 5350km) inner core T increases also, but not as fast T & P balanced so iron is molten rising P overcomes heat iron solid WORLD DISTRIBUTION OF EARTHQUAKES any pattern? SEISMIC BELTS Circum-Pacific belt: 80% of recorded quakes Mediterranean-Asiatic belt: 15% Seismic Belts = energy release other evidence of E release? volcanoes **combo of quakes & volcanoes = plate edges** DEPTHS OF EARTHQUAKE FOCII quakes below 670km? 2 groups: shallow-focus quakes: 0-70km most common more dangerous all seismic belts max. E released: gen. decreases w/increasing depth intermed-deep focus: 70-670km **BENIOFF ZONE** less common *convergent boundaries only outlines descending cold plate in subduction zone why no quakes below 670km? 670km discontinuity? ductile at depth? Other sources of information -GRAVITY ANOMALIES Gravity varies w/distance & mass: DISTANCE MASS earth = ellipsoid radius @ equator 21km larger so gravity slightly stronger at poles gravimeter So use gravity to find thickness of crust matches seismic data ocean crust density: 3.0 g/cc continental crust density: 2.7 g/cc for balance on the plastic asthenosphere crust “floats” on asthenosphere = isostacy continent crust is thick; thickest under mtns ocean crust is thin Page 28 Course Notes HEAT FLOW- shows convection cells in mantle (Return to Index) TECTONICS: the ruling Paradigm Development: early evidence - circumstantial but strong early objections? EVIDENCE FROM THE SEAFLOOR Hess: sea floor spreading #volcanoes: sea floor young ocean ridges: high heat flow, volcanoes, normal faults, unlike continental mountains = areas of formation of ocean crust ocean trenches: Benioff zones, areas ocean crust destroyed PALEOMAGNETISM magnetic minerals align with field + rock solidifies = record field @ time forms magnetic polarity location of continents relative to pole magnetic latitude apparent polar wander Vine & Matthews (& Morley) symmetric patterns of reversals along ridges + dates youngest at center (by corr. to land record) due to sea floor spreading gives rel. rate of plate motion (ridges also move) PLATE BOUNDARIES CONTINENT-CONTINENT DIVERGENT BOUNDARIES Extension ---- normal faults decompression melting: basalt, gabbro (granite), shield volcanoes thick continental sediments shallow quakes aulacogen: failed rift Triple junctions OCEAN-OCEAN DIVERGENT Extension ---- normal faults decompression melting: basalt, gabbro, shield volcanoes thin marine seds (evaporites) mid-ocean ridge: active edge of plate, hot, young, elevated continent margin: passive abyssal plain: old, cold, low elevation (deep-water) age~ depth Return to Index OCEAN-CONTINENT OR OCEAN-OCEAN CONVERGENT compression: thrust/reverse faults, folds subduction: increase water + increase T = melting: andesite, granite, makes continent crust, composite volcanoes; destroys ocean crust shallow-deep quakes lithic-rich seds meta rx: blueschist, amphibolite, granulite facies angle of subduction: changes stress in back-arc; steep angle - extension in back-arc & basalt accreted terranes conti-conti collisions & later rifting or island or conti frag hits subduction zone Page 29 Course Notes CONTINENT-CONTINENT CONVERGENT compression: reverse/thrust faults, folds shallow quakes no volc (granite) regional meta arkosic seds in clastic wedge TRANSFORM shear: strike-slip, mylonite, no ig., shallow focus HOT SPOTS over stationary mantle plume high T: basalt absolute speed of plate fastest - all ocean crust 3 main causes of volcanoes on Earth PLATE MOTION DRIVING FORCE(S) mantle convection How much of mantle convects? 3 models gravity assists: slab pull, ridge push Copyright 2002-2015 ©Kathleen Devaney Page 30
