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GLG 110 - Exam Cheat Sheet

Earth Sciences
Course Code
Lisa Tutty
Study Guide

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Geology Lecture #2 Outline: Plate Tectonics (-internal zonation of Earth [physical vs compositional], -theory of…, -evidence for, -3 types of plate boundaries [convergent, divergent, transform], -measuring plate velocities [magnetic field, hot spot tracks, direct
measurement],-why do plates float?, -what drives plate tectonics?. Plate Tectonics: Planet Earth divided up into compositional layers (A: solid inner core [1220 km], B: liquid outer core [2250], C: solid lower mantle [2230], D: partially molten upper mantle [670 km], E: crust
[16-40 km]). The Earth’s Interior: Systems of Zonation: Layers defined by physical properties: lithosphere (solid, rigid), asthenosphere (solid, weak, ductile [flowing]), mesosphere (solid), outer core (solid), outer core (liquid), inner core (solid). Earth’s interior
differentiated into three compositionally distinct layers: crust, mantle, core. (CH 1.3). How do we know this? Earthquakes (seismic waves) (CH 12.1;12.14;12.15;12.16). Lithoprobe – vibroseis trucks for investigating the interior of planet Earth. Oceanic crust vs.
Continental crust (oceanic crust is 7km thick, 7km/sec., think basalt. Continental crust, 30-50 km thick, 6km/sec., think granite. Lithosphere is divided into about 21 plates, some have continents as “passengers”. The lithosphere is interacting with the asthenosphere, the
mantle and the core. Some plates are moving apart, DIVERGING (North American Plate – Eurasian Plate). Hypothesis: Earth is divided into mechanical layers, outer layer is rigid lithosphere, floats atop plastic asthenosphere. Theory of Plate Tectonics – circa the
1960’s: proposes that Earth’s lithosphere is divided into plates (like the shell of a cracked egg) that move relative to one another, and relative to the underlying asthenosphere. As plates move, their interiors remain relatively intact, while their boundaries undergo
deformation. Plate tectonic forces give rise to the formation of the crust, affect continental positions, and produce changes in global topography, the slow inexorable wearing down of the land surface of the Earth would lead to its demise and reduction in height to sea level
in less than 20 million years owing to weathering and erosion, if it were not for the return of the materials to the continents via plate tectonic forces. Volcanoes (randomly distributed? “Ring of Fire”) (CH 3.3-3.4). Evidence for plate tectonics: continents were connected (-
matching coastlines, -similar rocks, glacial features “cross” oceans, -same fossils (ex, Glossopetris, Mesosaurus).Mountain belts (randomly distributed? Ex. Alps and Himalayas). Earthquakes (randomly distributed?) (CH 3.3-3.4). Plate Boundaries (CH. 3.3-3.4) Three
types of plate boundaries: divergent, convergent and transform. Convergent plate boundary: (CH.3.6) two plates coming together. Subduction: one plate pushes beneath another, often has ocean trench, volcanic arcs, mountains (Ex. W South America). Features depend
on king of lithosphere; ocean-ocean (Japan), ocean-continent (ex. S America), continent-continent (ex. Himalayas). Divergent plate boundary: two plates spreading apart. Mid-ocean ridge (ex. Iceland: MOR exposed). Continental Rift (ex. African Rift Valley). Transform
Boundary: two plates sliding past one another, connect convergent and divergent boundaries (ex. San Andreas Fault). Left strike-slip fault (everything looks like its moving left from all perspectives), and vice versa. Active transform fault: connects crests of mid-ocean
ridges, while fossil transform faults (=”fracture zones”) stretch away from mid-ocean ridges. Summary: lithospheric plates and plate boundaries. How do we measure plate velocities? (CH.3.8-3.9) Earth’s magnetic field (magnetic field is described as axial dipole, angle to
vertical changes w/ distance to magn. Pole), Apparent Polar Wander Path (CH.3.8-3.9) (continents move, rocks record change in inclination. Earth’s dipole field switches polarity (geodynamo: convection in outer core, magnetic time scale), Seafloor Anomalies (new sea
floor is being created at MOR, records direction of present field, reversals cause parallel bands. Oldest sea floor is only about 200 million years old [thickness of sediments, magnetic sea-floor anomalies]), Hot Spot Tracks (CH.3.10) (stationary mantle plumes, burn through
lithosphere, track volcanoes (ex. Hawaiian Islands) ), Direct Measurements (Present-day velocities) (CH.3.8) (repeat GPS measurements between same points. Close agreement of geologic with present day values.) Plate Tectonic Setting in Western Canada (convergent
ocean-continent. Transform boundaries connect to divergent ocean-ocean boundary). Why do plates float on asthenosphere? Icostasy (principle: a floating body displaces as much liquid as corresponds to its weight. Force balance: weight is balanced by buoyancy. –
blocks of same weight but different densities have same volume below water (CH. 1.3; 3.8; 11.1; 11.2), -blocks of same density but different height have same proportions above and below water. Pratt – shape of midocean ridges (new crust is higher but condenses the
farther away it gets and lowers), Airy – roots of mountains. Ex. light continental crust stands out of the water while dense oceanic crust is covered by water. Ex. as oceanic plate moves away from MOR, it cools down and becomes denser  ocean depth increases away
from MOR. Ex. Glacial Rebound – after glacial ice melts (which pushed downwards onto crust), the crust slowly bounces back up. What drives plate tectonics? (CH. 3.8) Earth is cooling down, subduction forces mantle convection (gravity pulls down on the plates.)
Lecture #5 Sedimentary Environments: Normal Fault: hanging wall going down. Sedimentary Environments: mountain environments, streams and rivers, sand dunes, wetlands, lakes, beach, coastal dunes, tidal flat, delta, submarine delta, lagoon, barrier islands, reef,
continental shelf and slope, deep seafloor. 3rd group of rocks: source  process  product. Sediments (ions in solution/animal shells)  deposited (or precipitated and cemented)  sedimentary rocks. Physical (near surface fracturing. Frost and mineral wedging. Thermal
expansion. Biological activity.) and Chemical (dissolution. Oxidation. Hydrolysis. Biological reactions) Weathering. Clastic Sediments: size, shape & sorting. Sediments come in all sizes (boulders, cobbles, pebbles, sand, silt, clay.) Characteristics of sediments (size of
particles [course to fine], rounding or angularity of particles [rounded to angular], sphericity of particles [spherical to tubular], sorting of particles [well sorted to poorly sorted]). How can we learn about ancient environments from sedimentary rocks? Made of rock
fragments, dissolved minerals, shells,… result of weathering (temp., ice, roots, water dissolves minerals) – quartz is very resistant, - iron silicates become iron oxides (ex. hematite), - feldspars break down and become clay minerals, -some minerals dissolve (ex. salt,
calcite).  rock/mineral fragments and dissolved ions. Clastic sediments are moved and deposited by water, wind, glaciers. Clastic sediments named by size (clay, silt, sand, pebbles, cobbles, boulders). Clastic sedimentary rocks are also named by grainsize:
(mudstone/shale, sandstone, conglomerate). Loose sediments - show structures (ex. ripples  how/where sediment was deposited), -need to be lithified (=made into rock) by weight of overlying sediments and cementation. Textures of clastic rocks: under microscope (ex.
sandstone shows rounded grains w/ cement in between), outcrop structures (ex. boulders [flood deposit atop layered fine sediment]). Clastic Sedimentary Rocks: conglomerate, breccia, sandstone, siltstone, shale. Types of natural cement: calcite, silica, clay minerals,
iron oxide minerals… NON-Clastic Sedimentary Rocks (precipitate by water or deposited by organisms): (carbonate) Limestones: Inorganic OR from animal remains, (Carbonate) Dolostone, gypsum, halite, BIF. Evaporites: evaporates can form in shallow, restricted
basins surrounded by fringing reefs. Sea water evaporates rapidly, precipitating salts. Evaporites: ions can form minerals if water evaporates ex: halite, gypsum (in lagoon), travertine (at hotsprings). Biogenic sedimentary rocks: especially marine organisms  limestone,
chalk. How are fossils formed? Most commonly.. shells buried and preserved unaltered (<100 million years) ,cavities filled with silica, calcium carbonate, iron – a process called (per) mineralization. (Per)mineralization: -die in or near water, -soft parts consumed by
bacteria, -sedimentation (fine grained = more detail, chemical makeup of rock =colour), -more sed’s pile on = pressure = rock, -mineral rich water = changes to the shell, -uplift, -erosion. Trace Fossils: -preserved tracks, trails, burrows, borings. Study of trace fossils =
ichnology, process of disturbing sediment = bioturbation. Fossils as clues to ancient environments: palaeoecology= study of ancient organisms and their environments. Clues from (fossil types, assemblages, fossil morphology, trace fossils). Fossils and stratigraphy:
how do we use fossils in stratigraphy? To establish relative age of rock units, correlate units. What information to we need to do this? –relative age of rock units, -fossil species present in each unit, -establishment of first and last appearance of each species geologic range.
Principle of Faunal Succession – William Smith. What kinds of fossils are most useful for stratigraphic work? –short lived, widespread, -assemblages (groups) of species – index fossil. Geologic Time Scale: most divisions of the geologic time scale mark major
environmental changes and associated biological changes (Appearance or extinction of species). Example of major environmental changes: changes in temperature and precipitation patterns, atmospheric composition, sea level. Such changes can be caused by: changes
in the amount of solar radiation, changes in the intensity of plate tectonics, volcanic eruptions, meteorite impacts, and human activities. Relative Time: stratigraphic principles (-original horizontality [steno], -superposition [steno], way up indicators, -Faunal succession
[smith], Lateral continuity [steno], cross-cutting relationships [lyell], law of inclusions [hutton]). Unconformities( -disconformities, non-conformities, -angular unconformities, -focus: Grand Canyon.) Absolute Time: Isotopic dating, age of Earth calculations. Geologic Time:
-absolute ages – impossible for early geologists (until the 20th century), -early geologists were able to determine only the relative ages of various parts of the Earth. For this they were using several principles: uniformitarianism, original horizontality, superposition, original
continuity, cross-cutting relations… Principle of original horizontality: -sedimentary rocks and lava flows are laid down parallel to Earth’s surface, -these layers begin essentially horizontal, -if rock layers are observed tilted at an angle or folded, the events that caused
this deformation occurred after the rocks were already deposited, -in other words, the rocks were deposited first and the folding came second. Principle of Superposition: (Nicolaus Steno): in sequence of undisturbed sedimentary rocks or lava flows, the oldest layer will
be at the bottom of the sequence with the youngest layer at the top, -each rock layer is older than the layer above it & younger than the layer below it, -it should make sense that sand, mud, or lava would spread out over a surface that is already there; therefore, the pre-
existing land surface is older. Law of Faunal Succession: -William Smith (1790): fossils of invertebrate animals found in the rock layers of the canals he was building appeared in a predictable sequences, -the fossil remains of living things are present in the rock layers at
definite intervals, and exist within a discrete period of time, -fossils occur in a definite, invariable sequence in the geologic record (if strata is undisturbed). Principle of Lateral Continuity: -sediments are deposited over a large area in a continuous sheet, -rock layers
extend continuously in all directions, until they thin out at the edge of the depositional basin, or grade into a different type of sediment. Principle of Cross-Cutting Relationships: -(James Hutton): if a fault or other body of rock cuts through another body of rock then it
must be younger in age than the rock through which it cuts and displaces, -applies to geologic features like faults, or intrusions of igneous rock or veins in minerals, or ancient erosions surfaces called unconformities that cut across pre-existing rocks. Law of Inclusions: -
(James Hutton) if a rock body contained fragments of another rock body, it must be younger than the fragments of rock it contained, -the intruding rock must have been there first to provide the fragments. Unconformity: -a buried erosion surface separating two rock
masses or strata of different ages, indicating that sediment deposition was not continuous, -in general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe any break in the sedimentary geologic
record, -an unconformity represents time during which no sediments were preserved in a region. The local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area, -the interval of geologic time not
represented is called a hiatus. Types of Unconformity: Disconformity: -a disconformity is an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition. Types of Unconformity: Non-conformity: -exists between
sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock, -if the rock below the break is igneous or has lost its bedding by metamorphism, the plane of
juncture is a nonconformity. Type of Unconformity: Angular Unconformity: -an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers.
Lecture #6 Economic Geology: The geology of Ontario – 4 layers (Layer I – Precambrian Plate Collisions and Mountains, Layer II – Lower Paleozoic Tropical Seas, Layer III – Pleistocene Glaciations, Layer IV – Present Day Built Landscape). History: First geologic
map( 1150 BC in Egypt, Produced for Ramesses IV by Ammenakhate and portrays Wadi Hammamat, showed a gold mining district in the Eastern desert). Georgius Agricola: 1494-1555, “Father of mining geology”, De Re Metallica published after Agricola’s death in
1556, the first textbook to bring a scientific approach to geological resources. William ‘Strata’ Smith: 1769-1839, canal engineer and made the first geology map in Britain 1815, the study of rock layers and the determination of their various ages. William Logan: 1798-
1875, ‘no coal problem’. Greenstone – Slave Craton, Superior Craton. VMS – Volcanogenic Massive Sulphides: all VMS deposits in Canada show evidence of formation close to ‘black smokers’ like at MOR. (1) seawater enters ocean floor rocks through cracks, (2)
seawater loses oxygen and potassium, (3) water is heated and loses calcium, sulphate and magnesium, (4) hot water picks up sodium, potassium and calcium, (5) Water reaches 350*C and boil, leaching iron, zinc, sulphur and copper from the surrounding mafic rocks, (6)
Hot mineral-rich waters rise to ocean floor and emerge as “black smokers” where they mix with cold oxygen-rich seawater. Dissolved metals and sulphur combine to form thick massive sulphide metal deposits (7) In “white smokers,” metals are deposited below the seafloor
leaving a hydrothermal fluid rich in white mineral anhydrite (calcium sulphate). In 1888, copper was discovered in the mountains around Britannia Creek, south of Squamish. Large scale mining began at Brittania Beach in 1905, and by 1929, the largest copper mine in the
British Empire was located here, beside the shores of Howe Sound. The mine closed in 1974, but part of its historical legacy has been the large amounts of toxic effluent it had deposited into Howe Sound. A rain of iron: formation of 2 Ga iron formations by bacterial
induced oxidation of dissolved ferrous iron released from MOR & volcanic arcs. The arms race between Britain and Germany leading to WWI in 1914 saw the building of “dreadnought” battle cruisers armoured with nickel-iron steel plate. Triggered expanded Canadian
nickel mining at Sudbury. Paleozoic/Mesozoic: Paleozoic (hard) and Mesozoic (soft) coals. Coal was first discovered in Canada in 1672 when reference to a “mountain of very good coal” near what is now Sydney in Cape Breton, NS appaeared in a book by Nicholaus
Denys, the Governor of Acadia. 1720 saw the first commercial mine opened near Port Morien to supply the fortress in Louisbourg. The first Canadian labour union was formed in Springhill, NS in response to hard coal mine working conditions and the 1891 Springhill
disaster when 121 men and boys died in an explosion. Heavy oil is oil from which the lighter components have been flushed by groundwater. This leaves heavy semi-solid bitumen that sticks to sand grains as is the case with the famous “tar sands” of northern Alta.
Canada has more oil than Saudi Arabia when heavy oil reserves are counted. Canada ranks second only to Venezuela in global ranking. Athabasca oil sand, Greek River formation. Oil and Gas Traps: Principle reservoir types in which oil and gas occur in Canada:
Anticline, normal fault, thrust fault, sandstone lenses, sandstone pinchout, unconformity, reef (a small patch reef). Canada’s oil is mostly Bitumen/heavy oil, not conventional oil. When pumping oil, a “horsehead” beam oil pumping unit is used, and to either side there are
water-injection wells to refill the oil space. Oil and Sand Deposits: The tar sands belt of Alta extends over some 140 000km2, an area larger than the state of Florida. Environmental Impacts of Oil Sands Mining: Evaporite minerals (1. Gypsum, 2. Sodium Chloride, 3.
Potassium chloride). Hot Spots: Diavik Mine showing the open working pit in a Kimberlite pipe. Kimberlite pipes intruded after 200 Ma when Pangea began to break up. Kimberlite Pipes – made after the breakup of Pangea.. these belts mark the western migration of the N
Amer plate over four mantle hot spots. Pipes ear New Liskeard along the Temiskaming Rift basin were intruded about 150 million years ago when this part of Canada was stretched as Pangea broke apart and the Atlantic Ocean began to widen. Glacial Dispersal Fans
and ‘Float’ Minerals: beginning the Pleistocene: the famous White Channel near the Klondike River valley, originally worked by powerful jets of water, larger volumes were processed with dredges. Some 12 million ounces of gold have been recovered to date. Ore
Deposits: Granitic plutons in continental crust (tin, tungsten, bismuth, copper), Back-arc basin (copper, zinc, gold, chromium), Magmatic arc (copper, gold, silver, tin, lead, mercury, molybdenum), Fore-arc basin (lead, zinc, copper), subduction zone (chromium), Oceanic
crust (manganese, cobalt, nickel), Mid-ocean ridge (copper, zinc). Hydrothermal Ore Deposits: formed when minerals precipitate out from hot water solutions at a range of temperatures and pressures. From the circulation of mineral rich hot water, near to a heat source.
The minerals are usually deposited in pre-existing cracks in the rock. Commonly volcanic heat source, can also be in the deep crust due to the intrusion of granite or as the result of an orogeny/metamorphism. The water concentrates the minerals into distinct zones, there
are usually many different minerals in one hydrothermal deposit. Ex. of hydrothermal mineral deposits: veins formed when volcanically heated water force their way up into a fracture. Magmatic Ore Deposits: formed as magmas differentiate (Bowen’s reaction series) ex.
Chromite (mineral) sinks to the bottom of a basaltic magma and accumulates in an almost pure layer. Sedimentary Ore Deposits: evaporite deposits from when lake water or seawater evaporates and leaves its dissolved mineral behind. Baking soda and borax come
from lake deposits. Placer Ore Deposits: placer deposits always contain minerals that originated elsewhere and were transported from their original source by water. Placer deposits form where flow slows down. Residual Ore Deposits: water table is low, it likely controls
the mineral deposition in that oxidation in both extensive and deep to promote extensive leaching. Residual ore deposits are the minerals left behind by the chemical weathering of a host rock.
Lecture #8 Geologic Time: Geologic Theory relating to time and the formation of the Earth: a brief history: -11th century: Persian geologist Avicenna (mountains formed after a long series of events pre-dating humans), -11th century: Chinese naturalist Shen Kuo (concept
of geologic or ‘Deep time’). Western Geologic Theory pre 1800s: -heavily based in Christian religion: -earth was created in 7 days, climate is fixed, till, sand and gravel = Dilivium (from Biblical Floods). Strict Biblical Interpretation of Earth’s History: (rocks and landscapes
result from Noah’s Flood). More than one flood recognized (new life created each time so each layer contains different life forms.) In 1658 Archbishop Ussher of Ireland gave an age of the Earth of about 5600 years, based on the study of Old Testament. Western Geologic
Theory Pre 1800s: -Catastrophism (Georges Cuvier, the idea that Earth has been affected in the past by sudden, short-lived, violent events, possibly worldwide.) Catastrophism replaced by Uniformitarianism: -James Hutton, 1788 Constant cycle of deposition, burial,
uplift, erosion & re-deposition. Same processes we observe today operated in the past. –Charles Lyell geologic change = steady accumulation of minute changes over enormously long spans of time (1830). –Charles Darwin (1830s) geology & evolution. Provided a lower-
bound estimate for the age of the Earth, based on the denudation of the Weald dome: ~300,000,000 years. (1) What are fossils and what can we learn from them? A fossil may be any evidence of life in the geologic past. Body fossils = direct evidence eg, bones, shells.
Trace fossils=indirect evidence, eg. Tracks, burrows, resting, coproliths. Fossilisation: is very unusual, usually an animal or plant is eaten (or decomposes). Hard parts (bones, teeth, horns, shells, or wood) may survive. Ammonite, petrified wood, “Tollund Man”. Soft-part
preservation is extremely uncommon, Permafrost, amber, dehydration, peat. Exquisite fossils found in fossil “lagerstatten.” Trilobite (Cambrian ~520 Ma), Archaeopterix (Jurassic ~155 Ma), small horse (Eocene ~47 Ma). Ancient Greeks recognized fossils embedded in
rocks now on tops of mountains, how did they get there? Archbishop Ussher 1581-1656: declared in 1625 that “Earth formed at 9 am on October 26th, 4004 B.C” Based on counting generations in the bible… Georgius Agricola, recognizes that fossils are remains of
marine organisms in 1531. Nicholas Steno (mountains can be raised and lowered, land can be conveyed from one place to another.”). Facies: means “appearance of” James Hutton 1726-97: (1) Recognized ‘unconformities’ within layers of rocks and the igneous origin of
granite, (2) proposed concept of ‘uniformitarianism’ (the present is the key to the past), (3) came into conflict with Abram Werner and ‘diluvialism’ and ‘catastrophism’. (2) The relative age of rocks: ‘Hutton’s Unconformity’ at Siccar Point in Scotland. Deposition of older
strata – deformation of strata in mountain building event, erosion to produce surface unconformity, deposition of younger strata, uplift, tilting, erosion. The Igneous Origin of Granite From Charles Lyell’s geology textbook ‘Principles of Geology’ 1830. John Playfair,
geologist (1747-1819); the concept of “Deep Time.The Great Unconformity: at Marmora, Ont. Precambrian: 1Ga, Pa: 450 Ma. Paleozoic on Proterozoic. An Angular Unconformity: 500 million missing years.. 1 billion under 500 million. The Big Debate of the 19th
Century: Catastrophism and Creationism vs Uniformitarianism and Evolution. 1790-1820: the industrial revolution. 1830’s: Discovery of the origin of coal: formed in situ from plant debris growing in swamps. Confirmed by discovery of in situ lithified tree trunks in coal
seams. Geologic Time: -absolute ages – impossible for early geologists (until the 20th century)., -early geologists were able to determine only the relative ages of the various parts of the Earth. For this they were using several principles: uniformitarianism, original
horizontality, superposition, original continuity, cross-cutting relations. The End Result: The ‘Geologic Column’ was put together piecemeal from sites around the world… hence lots of local names used for strata e.g. Niagara Formation, etc. Geologic Time Scale: the
construction of the geologic time scale was initially based on relative age determinations of sedimentary rock units (by using the principles of stratigraphy) and on correlations of widely separated units using fossils. Until the 20th century, only the relative ages were known.
(3) Absolute Age: Arthur Holmes (1890-1965) Pioneer of isotopic age dating (radiometric age dating) 1913 publishes “The Age of the Earth.” Geologic Time: Age of the Earth: -William Thomson (Lord Kelvin) provides an upper-bound estimate, based on the cooling of
the Earth from an initial high temperature to the present state: ~100,000,000 years. – however, the heat from radioactive decay had not been considered. –in 1896 Henri Becquerel discovers radioactivity. Radioactive isotopes are unstable. They undergo radioactive decay,
which converts them into a different element. – Radioactivity: the spontaneous emission of radiation, generally alpha or beta particles, often accompanied by gamma rays, from the nucleus of an unstable isotope. Radioactive dating of the Earth: - “daughter products form
from “parents” at characteristic rates of decay (half-lives), -ratio of daughter products to remaining parent material tells how much time has elapsed. Present estimate: 4.56 billion years old. (1) New discovery (Sept 2008) in northern Quebec (4.28 Ga basalt), (2) Acasta
Gneisses in northwestern Canada near Great Slave Lake (4.03 Ga), (3) Isua Supracrustal rocks in West Greenland (3.7-3.8 Ga). Important Processes: Parent isotope -> stable daughter isotope half-life value: Carbon14 -> Nitrogen14 = 5730 years, Uranium238 -> Lead206 =
4.5 billion years. Isotope: different ‘versions’ of an element having the same # of protons but different numbers of neutrons. Many isotopes are unstable and breakdown in various ways most commonly by losing protons and neutrons (radioactive decay). These differences
in mass can be measured with a mass spectrometer. Ex. Radiocarbon age dating: used to date organic material as old as 75,000 years. Corrections are needed for changing solar flux and variations in amount of C-14 produced in atmosphere. Geologic Time Scale:
EonEraPeriodTime (m.y.). Phanerozoic Mesozoic/Cenozoic  Cretaceous/Tertiary  65. Phanerozoic  Paleozoic/Mesozoic  Permian/Triassic  245. Proterozoic/Phanerozoic Paleozoic Cambrian 545. Precambrian Archean/Proterozoic  (..)(..)2,500. Precambrian
Hadean  (..)  (..)  3,800. Precambrian  Hadean  (..) (..) 4,600. (5) What have been the key steps in Earth’s evolution?: Hadean eon (4,560 to 4,400 Million years ago) – formation of Earth from impacts, -formation of Earth’s core (“iron catastrophe”), -large Mars-
sized impact rips out moon. Archean Eon: (4,400 to 2,500 Million years ago), -first continental crust (Ex. Acasta gneiss), -bacteria (anaerobic “extremophiles”) by 3,800 million years ago. Proterozoic Eon (2,500 to 545 Million years ago) –rise in atmospheric oxygen
~1,800 million years ago due to photosynthesis shown in change from “banded iron formations” to “red beds” (iron oxides), -eukaryotes by 1,600 million years ago (more efficient). Phanerozoic Eon (545 Million years ago to today), -“Cambrian explosion” (hard parts),
-subdivision based on fossil record, -at least 5 major mass extinction events. Paleozoic Era (545 to 250 Million years ago), -life conquers land: plants, lungs, reptile eggs. Mesozoic Era: (250 to 65 Million years ago) –time of dinosaurs, bipedal movement, birds, first
mammals. Cenozoic Era: (65 Million years ago to today) –time of mammals and of flowering plants. Mass Extinctions: -sudden drop in diversity, causes: anoxia due to global warming, meteorite impact, volcanic eruption, -especially severe for large animals, -small
number of species survives, -adaptive radiation during recovery phase. Eg. 65 Ma k/T boundary: volcano or impact? –Chicxulub crater, extinction at same time.
Lecture #9 Glaciers and Climate Change: Formation of glacier ice: glaciers form when snow accumulates. Snow (0.05-0.07), firn/neve (0.4-0.8), glacier ice (0.8-0.9) (density increase). For reference, water is 1. Firn/neve – snow which has survived a summer melt
season. Process takes 3~5 years on a temperate glacier (3m), and 3500 years on a polar glacier (depth of 130 m). Glacial Ice = 90% the density of liquid water. Glaciers: Mountain/Alpine (covers small areas, generally confined to mountain valleys, valley glaciers [ex.
Bylot Island, Can]), Continental (cover extensive areas, are not confined by topography, [ex. Antarctica]). Morphology of a Typical Glacier: wastage=ablation. Snow (annual accumulation layers undergoing burial), accumulation area (flowline), ablation area (surface
melt), melt water. A glacier accumulates snow in winter, and melts (wastes) ice in summer. Accumulation > wastage  advance. Accumulation <wastage  retreat. Ice within a glacier moves downhill by plastic flow – velocity profile. At the bottom of temperate glaciers, water
may lift and lubricate the ice, thus facilitating ice flow. Velocity of a glacier ranges from 2m/yr to 80m/day (surge). Flow…3 main components: (1) deformation of ice, (2) sliding, (3) deformation of bed. Zones in ice Caused by T & P differences … density. Even when
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