Final Exam Study Guide
Final Exam Study Guide GEOL 1302 - 002
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GEOL 1302 - 002
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This 56 page Study Guide was uploaded by Athraa_Alherbi on Sunday April 24, 2016. The Study Guide belongs to GEOL 1302 - 002 at University of Texas at Arlington taught by Cornelia Winguth in Fall 2015. Since its upload, it has received 37 views. For similar materials see EARTH HISTORY in Geology at University of Texas at Arlington.
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CHAPTER 1 Introduction • Why can we say that the Earth is a dynamic and evolving planet? 4.6 billion years) is preserved in geologic record o Examples from landscape and life history Continents moved about Earth’s surface – ocean basins opened and closed – mountain ranges formed • Shift in ocean and atmospheric circulation • Vegetation changes -First living cells between 4.6 and 3.6 billion years ago • Evolution of cell nuclei • Multicelled soft-bodied animals • Animals with skeletons and then backbones • Life moves from water onto land • Earth’s subsystems o Which are the 4 major subsystems, some of their characteristics? Atmosphere • Mixture of N, O, CO2, Ar, other gases • 99% in lower 30 km • Acts as “blanket”, filter, heat transport medium Biosphere • Zone of living things • Life is affected by environment • Life alters the environment Hydrosphere • Oceans • Glaciers • Ground water • Streams and lakes • Water vapor in atmosphere Geosphere • Crust • Mantle • Core – Outer core (liquid) – Inner core (solid) o Examples for some interactions between these subsystems *Plate movement affects size, shape, and distribution of ocean basins. Running water and glaciers erode rock and sculpt landscapes. *Evaporation, condensation, and precipitation transfer water between atmosphere and hydrosphere, influencing weather and climate and distribution of water. • Scientific method o What are scientific hypothesis/theory/model, and what are the main steps in developing them? • Universe o Big Bang: when did it happen, what is the evidence for it? – occurred approximately 14 billion years ago – created space and time • Evidence: – universe is expanding (– Galaxies are moving further from each other, and produce a red spectral shift • Doppler Effect) – background radiation of 2.7 Kelvin (“afterglow”) How do we determine the age of the universe? – measure the rate of expansion – backtrack to a time when the galaxies were all together at a single point • Name of our galaxy? MILKY WAY • Our solar system o Origin from solar nebula (when? 2008 by Fraser Cain 4.6 billion years ago) -huge rotating cloud of gas contracts and flattens -forms a disk of gas & dust with sun forming in center -eddies gather up material to form planets o Names of the planets o Subdivision into terrestrial and Jovian planets, differences between the two Terrestrial Planets – Mercury – Venus – Earth – Mars - small, composed of rock and metallic elements Jovian Planets – Jupiter – Saturn – Uranus – Neptune - large, composed of hydrogen, helium, ammonia, methane; condense at low temperatures • Differentiation of Earth o Why did it happen? * Earth heated up due to impacts, compression, radioactive decay *Molten iron and nickel sank to form the core * Lighter silicates flowed up to form mantle and crust o Main layers – core, mantle, crust, CHAPTER 1 & 3 Earth’s Layers and Plate Tectonics • Earth’s layers o Crust, mantle, core (outer and inner) – their approximate thicknesses and compositions Crust Composed of basalt and gabbro continental (20-90 km thick) oceanic (5-10 km thick) Mantle 2900 km thick 83% volume – composed largely of peridotite (iron & mg) Core – Solid inner region 1250 km thick - liquid outer region 2300 km thick --– iron and a small amount of nickel o What are lithosphere and asthenosphere? *Lithosphere – solid upper mantle and crust-- broken into plates that move over the asthenosphere *Asthenosphere – part of upper mantle – behaves plastically and slowly flows o Continental vs. oceanic crust CC is thicker and less dense then OC OC thin part of crust that underlies ocean basins • Wegener’s continental drift hypothesis o What did he propose, what was his evidence? hypothesis of continental drift (1912) =Shorelines of continents fit together • Supercontinent “Pangaea” =Matching marine, nonmarine and glacial rock sequences for all five Gondwana (=southern hemisphere) continents =Matching fossils, mountain ranges & glacial evidence o What was the problem that most scientists had with this hypothesis? main problem with Wegener's hypothesis of Continental Drift was the lack of a mechanism (couldn’t explain how they moved) • What is the theory of seafloor spreading? Harry Hess, in 1962, proposed the theory of seafloor spreading: – Seafloor separates at oceanic ridges where new crust forms from upwelling and cooling magma • Earth’s magnetic field o Where is it generated, what are its features? – magnetic poles generated frm electrical currents resulting from convection in liquid outer core – weak and horizontal at the equator – strong and vertical at the poles o How is the Earth’s magnetic field preserved in rocks? -Paleomagnetism: remnant magnetism in ancient rocks recording the direction and the strength of Earth’s magnetic field at the time of the rock’s formation o What are magnetic reversals? – present magnetic field is called normal, (with magnetic north near the north geographic pole) – reversed field at various times in the past: magnetic south near the north geographic pole o What are the ocean floor magnetic anomalies? striped, parallel to and symmetrical with the oceanic ridges • Age of oceanic crust • Plate tectonics o What are the major lithosphere plates? – lithosphere is rigid, consisting of oceanic and continental crust with upper mantle o What mechanisms drive plate tectonics? • convective heat system (different models) – “slab-pull” – “ridge-push” o 3 types of plate boundaries, their characteristics, some examples • Divergent plate boundaries, or spreading ridges: – plates are separating – new oceanic lithosphere is forming, (narrow sea to ocean) = Ex: East African Rift Valley *Convergent Boundaries - Where two plates collide, subduction often occurs – Subducting plate • moves into the asthenosphere • is heated • and eventually incorporated into the mantle ::Cont-Cont = mountains ex. Himalayas :: Cont-Oceanic = volcanoes ex. Andean Volcanic Arc South America :: Ocean – Ocean= oceanic trench ex. Transform Boundaries • plates slide laterally past each other, roughly parallel to the direction of plate movement • zone of intensely shattered rock • numerous shallow earthquakes Ex. San Andreas Fault Cali o Development of an ocean basin As a newly created narrow sea continues to spread, it eventually become expansive ocean basin =Example: Atlantic Ocean o How can ancient divergent and convergent plate boundaries be recognized? • Ophiolites consist of layers representing parts of the oceanic crust and upper mantle • What are hot spots and mantle plumes? Hot spots: – stationary columns of magma, originating deep within the mantle (mantle plumes) – slowly rise to the surface o Example: Hawaii • Relationship between plate tectonics and mountain building • Orogeny: – Episode of intense rock deformation or mountain building – results from compressive forces related to plate movement • During subduction, sedimentary & volcanic rocks are folded & faulted along the plate margin • Most orogenies occur along oceanic-continental or continental-continental plate boundaries • Relationship between plate tectonics and distribution of life forms? Physical barriers caused by plate movements include – intraplate volcanoes – island arcs – mid-ocean ridges – mountain ranges – subduction zones – Example: Isthmus of Panama creates a barrier to marine organisms CHAPTER 2 Minerals and Rocks • Elements o Composed of atoms; what are nucleus, protons, neutrons, electrons Atoms have – nucleus containing • protons – particles with a positive electrical charge • neutrons – electrically neutral particles – particles outside the nucleus • electrons – negatively charged particles o Atomic number, mass number, isotopes • Atomic number = the number of protons • Atomic mass number = number of protons + number of neutrons (which can vary) ISOTOPES : different forms of the same element (same # protons- Different # neutrons) • Chemical bonding o Ionic bonds (example: halite = table salt) • Ion – atom that has gained or lost one or more electrons – has a negative or positive charge –IONIC BONDS occur when electrons are TRANSFERRED between atoms o Covalent bonds (example: diamond) • Covalent bonding – results from SHARING electrons • Minerals o Definition • A mineral is: – Naturally occurring – Inorganic – Crystalline solid o Chemical composition written as formula (e.g. quartz: SiO2) • composition is shown by a chemical formula Quartz: SiO2 Ratio: 1: 2 o Crystalline structure: atoms arranged in 3D pattern *color, cleavage, hardness, luster, crystal form • Mineral groups o Silicates; examples • Silicates are minerals containing silica (Si and O) • make up almost 95% of Earth’s crust •olivine, pyroxene, amphibole, mica, clay, feldspar, quartz o Carbonates; examples •Carbonates are minerals with carbonate ion (CO3)-2 • calcite (CaCO3), constituent of limestone • dolomite [CaMg(CO3)2], constituent of dolostone • Rock cycle o 3 types of rocks Igneous, metamorphic, sedimentary o How can the rocks change from one type into another? Undergoing weathering, transportation, deposition • Igneous rocks o How do they form? What are magma/lava/pyroclastic material? o Extrusive vs. intrusive rocks • Extrusive or volcanic rocks – formed at the surface from lava or pyroclastic materials • Intrusive or plutonic rocks – formed from magma injected into the crust – or formed in place in the crust (rocks that crystallize from magma) o Fine-grained (aphanitic) rapid cooling vs. coarse-grained (phaneritic) texture slow cooling o Felsic (granite, rhyolite) vs. mafic (basalt, gabbro) composition Light to > Dark : felsic, intermediate, mafic, ultramafic High to > low silica : felsic, intermediate, mafic, ultramafic • Sedimentary rocks o Formation process of clastic (detrital) sedimentary rocks; examples: conglomerate, sandstone, shale • Clastic Sed. –composed of fragments or particles – known as clasts = Clastic texture • conglomerate – composed of gravel (>2mm) – with rounded clasts • sandstone – composed of sand • mudrocks, e.g. shale o What are chemical sedimentary rocks?; example: rock salt (evaporite) • Evaporites formed by – inorganic chemical precipitation during evaporation – Rock salt and rock gypsum – evaporites made of sodium chloride and gypsum o Formation of coal and limestone • Coal – made of partially altered, compressed remains of land plants accumulated in swamps • Limestone – carbonate rock made of calcite precipitated chemically or (most commonly) by organisms • Dolostone – carbonate rock made of dolomite usually altered from limestone • Metamorphic rocks o How do they form, and what changes in a rock during metamorphism? They form by undergoing agents of metamorphism such as :: • Heat • Pressure • Fluid activity is an important metamorphic agent as well o Contact metamorphism, affects a thin zone of country rock around an igneous intrusion o regional metamorphism at convergent plate boundaries occurs at moderate to deep levels under moderate to ultra-high pressures and high temps . o Foliation: what is it?; examples of foliated and nonfoliated rocks When rocks are subjected to differential pressure the minerals typically rearrange in a parallel fashion • Foliated texture – platy and elongate minerals aligned parallel to one another – caused by differential pressure –Slate, Phyllite, Schist, Gneiss • Nonfoliated texture – mosaic of roughly equidimensional minerals –Marble, Composed of calcite or dolomite metamorphosed from limestone or dolostone –Quartzite, Composed of quartz metamorphosed from quartz sandstone Chapter 5 - Rocks, Fossils, and Time • Stratigraphy -Stratigraphy deals with the study of any layered rocks and their • composition • origin • age relationships • geographic extent • Almost all sedimentary rocks are stratified o Principles of superposition and inclusion -Nicolas Steno (Principle of Superposition- oldest layer at bootom; youngest layer at top) • more difficult in deformed strata -inclusions or fragments in a rock are older than the rock itself (Principle of Inclusions) -Light-colored granite showing basalt inclusions (dark) o How can a lava flow be distinguished from a sill? Determining the relative ages of lava flows, sills and associated sedimentary rocks – uses contact metamorphism effects – and inclusions • conformable strata: – sequences of rocks in which deposition was more or less continuous • Unconformities – times of nondeposition and/or erosion that encompass long periods of geologic time, perhaps millions or tens of millions of years o What do they represent? What is a hiatus? • Rock record is incomplete at this location – Interval of time not represented by strata is a hiatus o What are disconformity, nonconformity, angular unconformity? Disconformity: • separating younger sedimentary from older sedimentary rocks, both of which are parallel to one another (ex. Jurassic rocks, Mississippian rocks) Nonconformity: • Erosional surface cut into metamorphic or intrusive rocks and covered by sedimentary rocks (ex. Cambrian flathead sandstone, precambrain granite) Angular unconformity: • Erosional surface on tilted or folded strata over which younger rocks were deposited (ex. Medial jurassic sandstone, upper Triassic red beds) • Sedimentary facies *body of sediment: – with distinctive physical, chemical, and biological attributes – deposited side-by-side with other sediments in different environments o What happens during a marine transgression/regression, how do layers change laterally and vertically? • A marine transgression – occurs when sea level rises with respect to the land –Rocks of each facies become younger in a landward direction during a marine transgression – Facies become time-transgressive • During a marine regression, – sea level falls with respect to the continent o What can cause sea level changes? • Uplift of continents causes regression • Subsidence causes transgression • Widespread glaciation causes regression – because of the amount of water frozen in • Rapid seafloor spreading, – expands the mid-ocean ridge system, displacing seawater and causing transgression • Diminishing seafloor-spreading rates – increases the volume of the ocean basins and causes regression • Ocean warming causes transgression – because of expansion of water • Fossils? • Fossils are the remains or traces of past life forms • They are most common in sedimentary rocks – but can be found in volcanic ash and volcanic mudflows • They are extremely useful for determining relative ages of strata – but geologists also use them to ascertain environments of deposition • Fossils provide some of the evidence for organic evolution (see Chapter 7) • The fossil record is the record of ancient life preserved as fossils in rocks o What are body fossils vs. trace fossils? • Fossils are the remains or traces of past life forms • They are most common in sedimentary rocks – but can be found in volcanic ash and volcanic mudflows • Remains of organisms are called body fossils. – bones, teeth and shells • TRACE FOSSILS: Indications of organic activity – tracks, trails, burrows, nests, fossilized feces o What is the principle of fossil succession? •Same principle as Superposition (oldest at the bottom, youngest at the top) Chapter 6 - Rocks as Archives of Earth History • How can an environmental interpretation be made? -- Observation and data gathering by visiting rock exposures (outcrops) and carefully examining • textures • composition • fossils (if present) • thickness • relationships to other rocks --- Interpretation: èDepositional Environment • Composition of rocks: o Common minerals in detrital rocks? What do they (and don’t they) tell us? Detrital rock composition tells about source rocks – E.g. quartz sand deposition possible in many different environments o Examples of composition of chemical sedimentary rocks, what do they tell us? Composition of chemical sedimentary rocks more useful in revealing environmental information – E.g. limestone (warm, shallow seas), evaporites (arid environments) • Texture of sedimentary rocks: o Correlation grain size – transport conditions Detrital grain size: some indication of energy conditions during transport and deposition o What are sorting and rounding, what do they tell us? Rounding: degree to which detrital particles have their sharp corners and edges worn away by abrasion Sorting: refers to the variation in size of particles making up sediment or sedimentary rocks – well sorted (e.g. by wind) – poorly sorted (e.g. by ice) • Sedimentary structures: – features that formed at the time of deposition or shortly thereafter – manifestations of the physical and biological processes that operated in depositional environments o Bedding: fine layers = laminations; what are graded bedding and crossbedding, how do they form? BEDDING Sedimentary rocks generally show bedding – Individual layers less than 1 cm thick are laminations • common in mudrocks – Beds are thicker than 1 cm • common in rocks with coarser grains GRADED BEDDING • Upward gradual decrease in grain size – Common in turbidity current deposits CROSS- BEDDING • Layers at an angle to the surface upon which they accumulate, as on the downwind side of a sand dune • Cross-beds: result from transport by either water or wind Cross-Bedding • Beds are inclined or dip downward in direction of the prevailing current o Ripple marks: wave-formed vs. current-formed • Ripple marks: small-scale alternating ridges and troughs, common on bedding planes, especially in sandstone • Wave-formed ripple marks – symmetrical • Current ripple marks – formed from wind or water flow and have asymmetry indicating the original flow direction o Mud cracks – where might they form? • Mud cracks: from drying and shrinking of clayrich sediments – require wetting and drying to form – cracking into polygonal patterns bounded by fractures o Examples for biogenic sedimentary structures; what is bioturbation? • Biogenic sedimentary structures include – tracks – burrows – trails • called trace fossils • Extensive burrowing by organisms: bioturbation – may alter sediments so thoroughly that other structures are disrupted or destroyed • What is a depositional environment? Continental, transitional, and marine environments o Continental: Deposition on continents (on land) might take place in – fluvial systems – rivers and streams – deserts – areas covered by and adjacent to glaciers § Fluvial: characteristics of braided vs. meandering stream Deposits of braided streams are mostly – gravel and cross-bedded sand bodies Mud is nearly absent • Braided stream deposits consist of – gravel – and cross-bedded sand – but mud is rare or absent • Meandering stream deposits– winding channels – mostly fine-grained floodplain sediments with subordinate sand bodies – point bar deposits over erosion surface • Meandering stream deposits: – fine-grained floodplain sediment is common – with subordinate sand bodies § Deserts: dunes, alluvial fans, playa lakes – how do they form? • Desert environments: association of features found in – sand dune deposits, – alluvial fan deposits, – and playa lake deposits • Windblown dunes : – well-sorted, well-rounded sand – cross-beds meters to tens of meters high – land-dwelling plants and animals make up any fossils • Alluvial fans form often along the margins of desert basins – streams and debris flows discharge from mountains onto a valley floor – triangular (fan-shaped) deposit of sand and gravel • More central part of a desert basin: – playa lake (temporary lake surface), in which laminated mud and evaporites accumulate § Glacial deposits: what are till, moraines, outwash, glacial varves? • Till: – poorly sorted, nonstratified, deposited directly by glacial ice – mostly in ridge-like deposits called moraines • Outwash: -- sand and gravel deposited by braided streams issuing from melting glaciers • Glacial Varves: --Glacial lake deposits show alternating dark and light laminations = varves – representing one year’s accumulation of sediment – light layers accumulate in spring and summer, dark layers in winter -- Dropstones – liberated from icebergs – may also be present o Transitional: § Deltas- Simple and Marine Deltas Simple- As delta builds outward, it progrades – vertical sequence of rocks – becomes coarser-grained from the bottom to top – bottomset beds may contain marine (or lake) fossils – topset beds contain land fossils Marine- Strongly influenced by one or more modifying processes – stream/river-dominated delta results – wave-dominated delta – tide-dominated deltas § Barrier islands and lagoons • On broad continental margins with abundant sand, long barrier islands lie offshore – separated from the mainland by a lagoon • Subenvironments of a barrier island complex: § What are tidal flats and their characteristics? • Tidal flats are present – where part of the shoreline is periodically covered by seawater at high tide and then exposed at low tide • One of their most distinctive features: – herringbone cross-bedding (sets of cross-beds that dip in opposite directions) o Marine: § What are shelf (inner: sandy, outer: muddy), shelf break, slope and rise? What kinds of sediments do we find here, where do they originate? What are turbidity currents? § What kinds of sediments do find in the deep sea, where do they come from? **STUDY PIC** • Continental shelf – High-energy inner part: mostly sand, cross-bedding, ripple marks, marine fossils and bioturbation – Low-energy outer part: mud, interfingering with sands • Much sediment derived from the continents crosses the continental shelf – funneled past the shelf break into deeper water through submarine canyons by turbidity currents – build-up of submarine fan DEEP SEA: – pelagic clay and ooze (calcareous or siliceous) – no sediment at mid-ocean ridges – sand and gravel are notably absent • Plankton (in siliceous and calcareous ooze): CALCAREOUS SILICEOUS ZOO PLANKTON FORAMINIFERA RADIOLARIA PHYTOPLANKTON COCCOLITHOPHORE DIATOM § Where does most limestone form? • most limestone is deposited in warm shallow seas on carbonate shelves and on carbonate platforms rising from oceanic depths • deposition occurs where little detrital sediment is present § Where and why do evaporites form? • Evaporites consist of – rock salt – rock gypsum • They are found in environments such as – playa lakes – saline lakes – (cut-off) ocean basins Chapter 4 & 5 - Geologic Time • What do relative dating and absolute dating mean? Geologists use two different frames of reference when discussing geologic time: Relative dating- Placing geologic events in a sequential order For hundreds of years geologists Numerical dating- Finding the age of a rock or geologic event in years before present • Relative dating principles: o What are the principles of superposition, original horizontality, lateral continuity, cross-cutting relationships? Superposition: The youngest rocks are at the top of the outcrop and the oldest rocks are at the bottom Original Horizontality: These sediments were originally – deposited horizontally – in a marine environment Principle of lateral continuity – Nicolas Steno’s third principle – Sediment extends laterally in all direction until it thins and pinches out or terminates against the edges of the depositional basin Principle of cross-cutting relationships – James Hutton (1726-1797) – An igneous intrusion or a fault must be younger than the rocks it intrudes or displaces Ex. The dike is younger than the granite, The fault is younger than the beds. • Relative geologic time scale: o How was the relative geologic time scale put together over time? **Other principles of relative dating – Principle of inclusions – Principle of fossil succession o What are lithostratigraphic units? Subdivisions: formations • Lithostratigraphic units are based on rock type • Basic lithostratigraphic element: formation – mappable rock body – distinctive upper and lower boundaries – Single rock type or variety of rock types EX. Capital Reef National Park, Utah o What are biostratigraphic units? Fundamental unit: biozone • Body of strata recognized only on the basis of its fossil content: biostratigraphic unit • Fundamental biostratigraphic unit: biozone o What are time-stratigraphic units? • Time-stratigraphic units: rocks deposited during a particular interval of geologic time • basic time-stratigraphic unit: system – used for construction of a composite geologic column that is the basis for the relative geologic time scale o What is correlation (lithostratigraphic and time-stratigraphic)? Lithostratigraphic Correlation • Correlation of lithostratigraphic units traces rocks laterally across gaps • Correlation of rock units based on – composition – position in a sequence – presence of distinctive key beds Time-stratigraphic Correlation • Range zone: total time of existence of a particular fossil group • Most useful are fossils that are easily identified, geographically widespread and had a rather short geologic range = guide fossils – E.g. Atrypa, Paradoxides (NOT Lingula) o Time units (from longer to shorter): eons, eras, periods, epochs • Certain parts of geologic time • Period is the most commonly used time designation (corresponds to time stratigraphic unit system) • Larger time units: era, eon • Shorter time units: epochs o Names of the three eras of the Phanerozoic Eon: Paleozoic, Mesozoic, Cenozoic Absolute dating: o What are isotopes in general as well as radioactive isotopes, parent isotope, daughter isotope? • Radioactivity is the spontaneous decay of an element to a more stable isotope • Radioactivity provides geologists with a powerful tool to measure numerical ages of rocks and past geologic events • Time it takes for one half of the atoms of the original unstable parent isotope to decay to atoms of a new more stable daughter isotope (during each half life parents atoms decrease by ½) o What is the half-life of a radioactice isotope? o How can the radiometric age be determined? o Which rocks can best be dated radiometrically? • Crystallization of magma separates parent atoms from previously formed daughters • This resets the radiometric clock to zero. • Then the parents gradually decay. Dating Metamorphism a. A mineral has just crystallized from magma. b. As time passes, parent atoms decay to daughters. c. Metamorphism drives the daughters out of the mineral as it recrystallizes. d. Dating the mineral today yields a date of 350 million years = time of metamorphism, provided the system remains closed during that time. o How can sedimentary rocks be dated indirectly? Radio carbon dating method o How does radiocarbon dating work, what can it be used for? • Carbon 14 is constantly forming in the upper atmosphere from nitrogen 14 • Carbon 14 becomes incorporated into organisms • While the organism lives it continues to take in carbon 14,but when it dies the carbon 14 begins to decay without being replenished o What is tree-ring dating? • Age of a tree can be determined by counting the annual growth rings • In cross-dating, tree-ring patterns are used from different trees, with overlapping life spans Chapter7 - Week 7 (Evolution) • Darwin’s theory of evolution by natural selection: o What were his main observations during the voyage of the Beagle? – fossil mammals in South America similar yet different from present-day llamas, sloths, and armadillos – finches and giant tortoises living on the Galápagos Islands vary from island to island and still resemble ones from South America o What was Lamarck’s possible explanation for variation? • Jean-Baptiste de Lamarck (1744-1829): – theory of inheritance of acquired characteristics o Who published a similar theory to Darwin’s at the same time? • Darwin and Alfred Russel Wallace (1823-1913) – theory of natural selection (presented simultaneously) • favorable variations in traits are more likely to survive and be passed on o What is the title of Darwin’s best-known publication? In 1859, Charles Robert Darwin (1809-1882) published On the Origin of Species o What are the main points of natural selection? • favorable variations in traits are more likely to survive and be passed on • Neo-Darwinism: o Incorporation of chromosome theory of inheritance (based on Mendel’s original work) Incorporation of chromosome theory of inheritance into evolutionary thinking – based on Mendel’s work on genes (1860s) – variations can be maintained/selected o Mutations as cause of variation changes in genes (mutations) as one source of variation – some induced by mutagens – some spontaneous o What are mutagens? Something that causes mutations • Definition of a species • Species: population of similar individuals that in nature interbreed and produce fertile offspring • Species are reproductively isolated from one another • What is allopatric speciation? • allopatric speciation: species arise when a small part of a population becomes isolated from its parent population • Evolutionary trend = series of adaptations to changing environment • What is a “living fossil”? Examples? • Several organisms have shown little or no change for long periods • living fossils • For example: – Latimeria (fish) – Gingko trees – Lingula • Linnaeus’ classification categories ^^^LOOK AT PIC ^^^ GEOL EXAM 3 REVIEW Precambrian Earth and Life History • What is the Precambrian? What are its eons, when did they start and end? Informal but widely used, three eras are Hadean ( 4.6-4.0 BYA), Archean ( 4.0- 2.5 BYA), and proterzoic (2500 542 MYA) • How and when was the Moon formed? • Shortly after accretion from planetesimals • Earth rapidly rotating, hot, barren, waterless, bombarded by meteorites and comets, no continents, intense cosmic radiation , and widespread volcanism • Formation of the Moon (between 4.6 and 4.4 billion years ago) from huge impact • How old is the oldest dated rock? – Acasta Gneiss in Canada (about 4.0 billion years) • What is a craton, what are its parts? • Cratons: a continent’s ancient nucleus, made up of shield and platform; little deformation since the Precambrian • Precambrian shields: areas of exposed ancient rocks • Platforms: buried Precambrian rocks • What are the most common Archean rocks, and what are greenstone belts? Mostly granite-gneiss complexes • Very special: Greenstone belts (low-grade metamorphic, originally volcanic and sedimentary rock units), – about 10% of Archean rocks – contain ultramafic lava flows Archean Rocks • Greenstone belts formed from (very fast) Archean plate movement • Canadian Shield = oldest part of North America; formed out of several cratons Several cratons formed similarly to the southern Superior craton and are found in the older parts of the Canadian shield • Earth’s Archean atmosphere: o What did the earliest gases not stay around Earth? How did then an atmosphere develop, and what were its main gases? • Probably composed of hydrogen and helium (the most abundant gases in the universe) • Swept away by the solar wind and lost into space • Once a magnetosphere was present, an atmosphere began accumulating as a result of outgassing • early atmosphere rich in carbon dioxide, and probably ammonia (NH3) and methane (CH4) • Where did Earth’s water come from? • some of Earth’s surface water from outgassing • some of Earth’s surface water from meteorites and icy comets • What are the oldest fossils (age, kind)? • Earliest fossils from Archean rocks are 3.5 billion years old • Chemical evidence for organisms in 3.8 billion years old rocks in Greenland • first organisms were anaerobic archaea and bacteria (prokaryotic cells) • What are the processes that led to oxygen enrichment in the atmosphere? • Photochemical dissociation and photosynthesis added free oxygen to the atmosphere o Which structures point towards the presence of photosynthesizing organisms, and what is the name of the organisms that produced them? • Present-day stromatolites: sticky mats of photosynthesizing cyanobacteria trap sediment [Stromatolites (Algal Mats)] • Oldest known undisputed stromatolites: found in rocks in South Africa that are 3.0 billion years old • Growth of Laurentia (-what is that?-) in the Proterozoic through accretion and orogenies; final stage: Grenville orogeny • Laurentia consisted of what is now North America, Greenland, parts of northwestern Scotland, and perhaps some of the Baltic shield of Scandinavia Growth of Continents, e.g. Laurentia • Paleoproterozoic: Collisions among various plates formed several orogens • What is the Wilson cycle? • Rocks of the Wopmay orogen in northwestern Canada and the Penokean orogen in the Great Lakes region are important because they record the opening and closing of an ocean basin (Wilson cycle) • What is the Midcontinent Rift in North America? • Beginning 1.1 billion years ago, tensional forces opened the Midcontinent rift - a failed rift • When was the present style of plate tectonics probably established? • A supercontinent consists of at least two continents merged into one Proterozoic Supercontinents (2bya) • Present style of plate tectonics involving opening and then closing ocean basins established by the Paleoproterozoic (as shown by ophiolites) • What is the oldest commonly recognized supercontinent, when did it form? • First commonly recognized supercontinent: Rodinia, assembled between 1.3 and 1.0 billion years ago and then began fragmenting 750 million years ago • What is the “Snowball Earth”? • Some geologists think that glaciers covered all land in the Late Proterozoic and all seas were frozen, resulting in a snowball Earth • How did the atmosphere evolve in the Proterozoic? • Cyanobacteria (the first oxygen-producers) present during the Archean, but stromatolites did not become common until about 2.3 billion years ago • Atmosphere became oxidizing: evidence: banded-iron formations, red beds o What are banded-iron formations (BIFs)? • Banded iron formations (BIFs): – alternating layers of iron-rich minerals and chert – Some in Archean rocks, but about 92% of all BIFs formed during the interval from 2.5 to 2.0 billion years ago o Which rock formations are evidence for oxygen enrichment in the atmosphere? banded-iron formations, red beds • red sandstone or shale colored by iron oxides, especially hematite (Fe2O3) Continental Red Beds Red mudrock in Glacier National Park, Montana • onset of red bed deposition in the Proterozoic coincides with the introduction of free oxygen into the atmosphere • Why did evolution happen relatively slowly until the Mid- Proterozoic? • Archean fossils: archea and bacteria • Paleoproterozoic fossils: same organisms, although stromatolites became common Life of the Proterozoic – prokaryotic cells reproduce asexually and do not share their genetic material, so evolution is a comparatively slow process • Eukaryotic cells (with cell nucleus) probably evolved in the Mesoproterozoic from the symbiosis of prokaryotes, and the tempo of evolution increased markedly • Major step in evolution of life forms in the Proterozoic: eukaryotic cells • Eukaryotic cells (with cell nucleus) probably evolved in the Mesoproterozoic from the symbiosis of prokaryotes, and the tempo of evolution increased markedly • Many eukaryotes are multicelled and aerobic • Most eukaryotes reproduce sexually o How might they have formed? o Oldest known eukaryote: Bangiomorpha (when?) • Oldest known eukaryotes: Bangiomorpha, found in 1.2 billion year old Mesoproterozoic rocks in Canada o What are acritarchs? • Hollow fossils known as acritarchs were probably cysts of planktonic algae and became common during the Meso- and Neoproterozoic • What were some advantages of multicellular vs. single-cell organisms? • Larger size • Multicelled organisms live longer, because cells can be replaced and more offspring can be produced • Cells have increased functional efficiency • What is the Ediacaran fauna? • First relatively controversy-free fossils of animals come from the Ediacaran fauna of Australia (600-545 million years old) and similar faunas of similar age elsewhere • Ediacaran-type fossils are found in Mistaken Point Formation, Newfoundland Paleozoic Earth History • When did he Paleozoic start and end? What are the periods of the Paleozoic? • The Early Paleozoic includes the Cambrian, Ordovician, and Silurian periods. • Paleozoic history of continents: mountain building at margins, major trans- and regressions; what are epeiric seas? Epeiric Sea is a shallow sea that covers a large part of a continent. • Each continent can be divided into two major components: – a craton (with the exposed shield and the sedimentcovered platform) and one or more mobile belts • Sediments deposited in widespread shallow seas (=epeiric seas) • Mobile belts: elongated areas of mountain building activity located along the margins of continents • How many continents were there at the beginning of the Paleozoic? What are their major components? What do the continents of Laurentia and Gondwana correspond to (today)? Baltica - Russia west of the Ural Mountains and the major part of northern Europe China - a complex area consisting of at least three Paleozoic continents that were not widely separated and are here considered to include China, Indochina, and the Malay Peninsula Gondwana - Africa, Antarctica, Australia, Florida, India, Madagascar, and parts of the Middle East and southern Europe Kazakhstan - a triangular continent centered on Kazakhstan, but considered by some to be an extension of the Paleozoic Siberian continent Laurentia - most of present North America, Greenland, northwestern Ireland, and Scotland Siberia - Russia east of the Ural Mountains and Asia north of Kazakhstan and south Mongolia • Major glaciation in the Paleozoic: in the Ordovician and Carboniferous in Gondwana Gondwana moved toward the South Pole (glaciation) • What are cratonic sequences, how do they form? A cratonic sequence is a very large-scale lithostratographic sequence that covers a complete marine transgressive-regressive cycle across a craton • Sedimentary-rock record of North America can be subdivided into six cratonic sequences (= representing a major transgressive regressive cycle) • Where was North America located in the Cambrian? Cambrian: North America straddled the equator the Sauk sequence) • Transcontinental Arch • North American cratonic sequences: o Sauk Sequence: by end of Sauk transgression (Late Cambrian), North America was almost completely covered by shallow sea o Tippecanoe Sequence: Middle Ordovician to Early Devonian ! What are the characteristics of the Michigan Basin? When and how did evaporites in the basin form? • Transgressing sea deposited the Tippecanoe sequence over most of the craton during the Middle Ordovician-Early Devonian • Basal rock: St. Peter Sandstone – resulted from weathering and erosion of Proterozoic and Cambrian sandstones deposited during the Sauk transgression • Tippecanoe basal sandstones followed by widespread carbonate deposition • Result of deposition by calcium carbonatesecreting organisms • corals • brachiopods • stromatoporoids • bryozoans • Middle Silurian rocks of the Michigan Basin: famous for their reef and evaporite deposits o Kaskaskia Sequence: Devonian reef complex in Canada, then widespread black shales in North America (how do black shales form?) Middle and Late Devonianage reefs of western Canada began forming as the Kaskaskia Sea transgressed southward into western Canada Basal units of the Kaskaskia sequence in eastern and north-central United States Extent of the upper Devonian and Lower Mississippian Chattanooga Shale and its equivalent units Upper Devonian New Albany Shale, Button Mold Knob Quarry, Kentucky • undisturbed anaerobic bottom water, • a reduced supply of coarser detrital sediment, • and high organic productivity in the overlying oxygenated waters o Absaroka Sequence: Late Carboniferous to Early Jurassic • Rocks deposited during the Pennsylvanian through Early Jurassic • Absaroka Sea retreated southwestward to New Mexico and Texas • North American mobile belts: o Appalachian mobile belt: What is the Iapetus Ocean and its role in orogenies (= mountain building) – Taconic and Acadian orogenies in Appalachians, Caledonian orogeny in Europe (formation of Laurasia)? o Cordilleran mobile belt: Antler orogeny in the Devonian (accretion of an island arc) o Ouachita mobile belt: Ouachita orogeny = final phase of collision between Laurasia and Gondwana • Devonian: widespread reddish fluvial sediments in eastern North America and northern Europe (after Acadian orogeny, from erosion of highlands): Old Red Sandstone, Catskill Delta – those are clastic wedges • Erosion of the resulting highlands – vast amounts of reddish fluvial sediments that covered large areas of northern Europe • Old Red Sandstone – and eastern North America • the Catskill Delta • Carboniferous: characterized by vast coal deposits – where and why? • Gondwana moved over the South Pole, resulting in extensive continental glaciation • Gondwana continued moving northward and collided with Laurasia • Carboniferous coal basins in equatorial zone: eastern North America, western Europe, and the Donets Basin of Ukraine • Temperate zone coal: Siberia • Upper Carboniferous (Pennsylvanian): formation of Ancestral Rockies through uplift • Series of fault-bounded uplifted blocks formed the Ancestral Rockies • Permian: assembly of Pangea; what is Panthalassa? • Assembly of Pangaea completed • Terranes and continental blocks of the eastern half of Pangaea somewhat controversial • Pangaea was surrounded by subduction zones • Panthalassa, an enormous single ocean, surrounded Pangaea o widespread arid conditions • Formation of a single large landmass had climatic consequences for the continent: arid and semiarid conditions widespread middle and upper Permian?) o in North America: three marine basins (part of Absaroka Sea) in New Mexico and Texas, characterized by reefs and evaporates Maria, Delaware, and Midland Basin Paleozoic Life History • What is the “Cambrian Explosion”? • Beginning of the Paleozoic Era: – animals with skeletons appeared “abruptly” in the fossil record • "Cambrian explosion” o What are the advantages of an exoskeleton? (1) Protection against ultraviolet radiation, allowing animals to move into shallower waters (2) Prevention of drying out in an intertidal environment (3) Allows increase in size and provides a place for attachment of muscles (4) Protection against predators • Marine ecosystem: o What are plankton and nekton? • Pelagic – Plankton: the small and microscopic organisms drifting or floating in the sea or fresh water, consisting chiefly of diatoms, protozoans, small crustaceans, and the eggs and larval stages of larger animals. Many animals are adapted to feed on plankton, especially by filtering the water. – Nekton: aquatic animals that are able to swim and move independently of water currents. • Benthos – Epifauna – Epiflora – Infauna – Sessile – Mobile o What are epifauna, infauna, sessile and mobile organisms? Infaunal meaning a shellfish, usually with a smooth shell, that burrows within sediment(burrower) Epifaunal meaning a shellfish usually spined that lives above the ground(nonburrower) Sessile animals are usually permanently attached to a solid substrate of some kind, such as a part of a plant, a dead tree trunk, or a rock. For example, barnacles attach themselves to the hull of a ship, but corals lay down their own substrate. Cannot move freely Mobile means they can move freely o What are the four feeding strategies found in the marine environment? suspension-feeding, herbivores, carnivore-scavengers, sediment-deposit feeders o What are trophic levels, producers, consumers, decomposers? Trohpic levels: • Showing the relationships among the – producers, – consumers, – and decomposers Producers: Photosynthesizing organisms (plants) Consumers: any organism that can’t make its own food, Consumers have to feed on producers or other consumers to survive. Decomposers: An organism that primarily feeds on dead organisms or the waste from living organisms • Trilobites: o When did they first appear and thrive? How did they live? • Trilobites: about half of the total fauna of the Cambrian • benthonic, mobile, sediment-deposit feeders that crawled or swam along the seafloor Trilobites • first appeared in the Early Cambrian, rapidly diversified, reached their maximum diversity in the Late Cambrian, and then suffered mass extinctions near the end of the Cambrian from which they never fully recovered • Brachiopods: o What are those?; abundant in Ordovician, used as guide fossils • Cambrian brachiopods – mostly primitive types called inarticulates – chitinophosphate shell Brachiopods • articulate brachiopods: – tooth-and-socket arrangement – were also present but did not become abundant until the Ordovician Period • What are archaeocyathids, when did they live? • archaeocyathids – benthonic sessile suspension feeders – constructed small reef-like structures at the beginning of the Cambrian – went extinct at the end of the Cambrian • What is the Burgess Shale famous for? Why is fossil preservation so good? • 1909: Charles D. Walcott discovered the first soft-bodied fossils from the Canadian Burgess Shale • more complete picture of a Middle Cambrian community than deposits containing only fossils of the hard parts of organisms • Deposition at base of a steep submarine escarpment • Animals lived in and on mud banks that formed along the top of this escarpment • Periodically, this unstable area would slump and slide down, depositing the animals in a deep-water anaerobic environment • Acritarchs: major phytoplankton group of the Paleozoic • Increased diversity and abundance of acritarchs – organic-walled phytoplankton – major phytoplankton group of the Paleozoic Era – primary food source of the suspension feeders • Silurian/Devonian reef builders: stromatoporoids and corals Reconstruction of a Middle Devonian reef from the Great Lakes area – with corals, cephalopods, trilobites, crinoids, and brachiopods Corals-a hard stony substance secreted by certain marine coelenterates as an external skeleton, typically forming large reefs in warm seas. sedentary coelenterate of warm and tropical seas, with a calcareous, horny, or soft skeleton. Most corals are colonial and many rely on the presence of green algae in their tissues to obtain energy from sunlight. Stromatoporoids- an extinct, sessile, corallike marine organism of uncertain relationship that built up calcareous masses composed of laminae and pillars, occurring from the Cambrian to the Cretaceous. Stromatoporoidea is a class of aquatic invertebrates common in the fossil record from the Ordovician through the Devonian. They were especially abundant in the Silurian and Devonian. • Transition from water to land: o When did it happen for plants and animals? What was the major barrier? • Transition from water to land required that several barriers be surmounted: – desiccation, – reproduction – effects of gravity – extraction of oxygen from the atmosphere by lungs rather than from water by gills • Crossopterygians: – backbone – limbs that could be used for walking – lungs that could extract oxygen • Fish: most primitive vertebrates • Most primitive vertebrates are fish – some of the oldest fish remains are found in Upper Cambrian Deadwood Formation (northeastern WY) – phosphatic scales and plates of Anatolepis Fish • Cambrian and Ordovician fossil fish from shallow nearshore marine deposits, • earliest nonmarine (freshwater) fish remains found in Silurian strata o Devonian: “Age of fish” • Many fish evolved during the Devonian Period (informally called “Age of Fish”) • Arrangement of fin bones for (a) a typical ray-finned fish (b) a lobe-finned fish – Muscles extend into the fin, allowing greater flexibility o What were the evolutionary advantages of developing jaws? • Evolution of jaws was a major evolutionary advantage among primitive vertebrates – jawless ancestors (ostracoderms) could only feed on detritus – jawed fish could chew food and become active predators • Evolution of the jaw may have been related to respiration rather than feeding: – evolving joints in the forward gill arches, jawless fish could open their mouths wider (greater oxygen intake) – also increased food consumption • Evolution of some lobe-finned fish to amphibians (tetrapods = first vertebrates on land in Devonian) • “Fishapod” has characteristics of both fish and tetrapods – gills and fish scales, broad skull, eyes on top of its head, flexible neck and large ribcage (to support its body on land or in shallow water), and lungs • Beginning of a true tetrapod forelimb – functional wrist bones and five digits, modified ear region • Evolution of amphibians to reptiles (Carboniferous) – Amphibians underwent rapid adaptive radiation and became abundant during the Carboniferous and Early Permian Large labyrinthodont amphibian Eryops – Labyrinthodonts were abundant during the Carboniferous in swampy conditions • End-Permian mass extinction: largest in Earth history; possible causes? End of the Permian: • most severe • about 90% of all marine invertebrate species and more than 65% of all land animals became extinct • Mass extinctions were gradual from a human perspective • Climate changes, rather than a single catastrophic event, were primarily responsible • Widespread continental fissure eruptions released carbon dioxide into the atmosphere, leading/ contributing to increased climatic instability • Sluggish ocean circulation • Combination of interconnected and related geologic and biologic events • Plant evolution: o What were the major adaptations for transition from water to land? o What was the new trait of gymnosperms? o most plants in swampy areas, but e.g. Glossopteris grew on higher ground • Adaptations for transition from water to land: – appearance of leaves – heterospory – secondary growth – emergence of seeds • Gymnosperms occupying higher and drier ground – cordaites (extinct at end of Permian) • Glossopteris – famous plant (seed fern) abundant in Gondwana Geol Exam 4 Mesozoic Earth History • What are the periods of the Mesozoic, when did it start and end? 251-66 MYA Triassic, Jurassic, Cretaceous • Breakup of Pangea: o Triassic: separation of North America from Africa, the North America from South America • Late Triassic and Jurassic: Antarctica and Australia began separating from South America and Africa; India began rifting from the Gondwana continent o Jurassic: Gondwana starting breaking apart • Late Jurassic: South America and Africa began separating o Cretaceous: globally high sea level due to increased rifting and heat flow Australia and Antarctica had separated, India was nearly at the equator, South America and Africa were widely separated, and Greenland was essentially an independent landmass • North America in the Mesozoic: o East coast: weathering of Appalachians, sediment-filled fault-block basins as result of rifting, lava flows and intrusion of sills (example: Palisades in New York) o Gulf area: more than 1000 m of evaporites (restricted basin in Jurassic), part of Cretaceous Interior Seaway in Cretaceous (widespread reefs) o Western region: Sonoma Orogeny and thrusting in the Jurassic; starting in Late Jurassic: westward movement of North America over Farallon Plate, subduction zone, leading to Cordilleran Orogeny (in several phases); related emplacement of batholiths (what are those?), Keystone Thrust Fault in Nevada; accretion of terranes (what are those?) o Mesozoic sediments in the west: regressing shallow sea in Triassic, leading to deposition of limestones, evaporites, dunes (e.g. Navajo Sandstone in Zion National Park), Morrison Formation (world’s richest Jurassic dinosaur fossil assemblage) Mesozoic Life History • Mesozoic: known as “Age of Reptiles” – what kinds of reptiles lived at that time? • Reptiles first appeared during the Early Carboniferous – when they first evolved from amphibians, they did not look very different from their ancestors. • Two dinosaur orders are distinguished based primarily on their type of pelvis: • Saurischia • Ornithischia Dinosaur Orders • Saurischian dinosaurs: – lizardlike pelvis – thus called lizardhipped dinosaurs • Ornithischians: – birdlike pelvis – thus called bird-hipped dinosaurs • theropods were carnivores, all others were herbivores • Mesozoic invertebrates: o Common guide fossils: Ammonites (belong to cephalopods), belemnoids (ancient squid), foraminifera (zooplankton) o coccolithophores very important as phytoplankton • Early Triassic invertebrate fauna not very diverse • Late Triassic: abundance in invertebrates • Mollusks most important Mesozoic marine invertebrates (also as guide fossils): – cephalopods – bivalves – gastropods • Mesozoic plants: o evolution of angiosperms (flowering plants) in Late Jurassic/Early Cretaceous o coevolution with insects (essential for pollination) Primary producers on land - • Seedless vascular plants and gymnosperms dominated Triassic and Jurassic land plant communities. • Early Cretaceous (perhaps Late Jurassic): – angiosperms (flowering plants) • Fossil record of earliest angiosperms sparse – precise ancestors remain obscure Angiosperms Archaefructus sinensis Lower Cretaceous rocks in China • Angiosperms widely adapted – flowers attract animal pollinators, especially insects – enclosed seeds • Coevolution between flowering plants and insects – Changes in one induced by the other referred to as coevolution • Mesozoic reptiles: o archosaur: common ancestor for dinosaurs, pterosaurs (flying reptiles), crocodiles, birds – what are their common characteristics? o dinosaurs: probably successful because of upright posture § saurischia vs. ornithischia – what’s their main difference? • Two dinosaur orders are distinguished based primarily on their type of pelvis: • Saurischia • Ornithischia • Saurischian dinosaurs: – lizardlike pelvis – thus called lizardhipped dinosaurs • Ornithischians: – birdlike pelvis – thus called bird-hipped dinosaurs • theropods were carnivores, all others were herbivores § only theropods were carnivorous (such as Tyrannosaurus) § sauropods: largest land animals ever discovered • Among the sauropods: – giant, quadrupedal herbivorous dinosaurs such as Apatosaurus, Diplodocus, and Brachiosaurus § famous ornithischia: Triceratops, Stegosaurus, • bird-like pelvis Ornithischian Dinosaurs • no teeth in front of the mouth • ossified (bone-like) tendons in the back region Duck-billed dinosaurs • Group of ornithopods with flattened bill-like mouths and crests or other ornamentation (for some) o flying reptiles: pterosaurs- what were their adaptations for flying; differences-pterodactyl vs. pteranodon? • pterosaurs = flying reptiles – Common from the Late Triassic until their extinction at the end of the Cretaceous • Pterodactyl: a long-tailed Late Jurassic pterosaur – wingspan ranged from 50 cm to 2.5 m • Evolution of birds: Archaeopterix (had feathers) -probably earliest bird • Probable relationships between reptiles and birds: – shelled, yolked eggs – skeletal features such as the way the jaw attaches to the skull From Reptiles to Birds • Since 1860: fossils recovered from the Solnhofen Limestone of Germany that provide evidence for reptile-bird relationships: – feathers – wishbone, consisting of fused clavicle bones, typical of birds – most other physical characteristics closely resemble small theropod dinosaurs • Archaeopteryx – birds by definition, but their numerous reptilian features convince scientists that their ancestors were among theropods • Mesozoic mammals: since Late Triassic • Therapsids (reptile group) diversified into many species of herbivores and carnivores during the Permian • Most mammal-like: cynodonts; by the Late Triassic time mammals evolved from them • Mammals evolved during the Late Triassic, not long after the first dinosaurs appeared, but for the rest of the Mesozoic Era most of them were small • End-Mesozoic mass extinction: what is the main theory for it, what is the evidence? • Greatest mass extinction: end of the Paleozoic Era • Another big mass extinction: end of the Mesozoic Era; among its casualties:– dinosaurs – flying reptiles – marine reptiles – several kinds of marine invertebrates, including ammonites • End-Mesozoic Extinction Proposal in 1980: Meteorite impact as main cause– bas
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