GEOL120 - Lecture notes 1-14 PDF

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GEOL120 lecture notes at CSU. Weekly lectures are combined into topics. Teacher was Sean Bryan....

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Ch. 1 - Plate Tectonics Tuesday, August 29, 2017

3:28 PM

Chapter 2 - Beginning Questions ○ What makes up a tectonic plate?  The crust and the upper part of the mantle (Lithospheric mantle) ○ Which is denser? Ocean crust or continental crust?  Ocean crust, based on its composition. □ Continental crust floats higher on the mantle, while ocean sinks further down ○ Which is thicker? Ocean crust or continental crust?  Continental crust is thicker □ Continental composition is similar to granite, ocean crust is similar to basalt ○ Which types of plate boundaries most likely have earthquakes?  All of them □ Each type has common earthquakes, we can actually map out plates based on earthquakes ○ Which type of plate boundaries are you most likely to find volcanoes?  Ocean-Continental Convergent and Ocean-Ocean Divergent □ The magma comes through rifts and subduction ○ Which type of plate boundaries would you find mountains.  Ocean-Ocean divergent, Ocean-Continental convergent, Continental collision - Plate Boundaries ○ Convergent  Ocean plate subducts under continental  Crust above lithosphere above Asthenosphere  Earthquakes occur along the boundary between subduction points  Trench is a deep ocean trench  Accretionary prism - the material scrapped up when plates converge  Melting magma will travel up continental plate and create volcanoes  Mountains created near boundary due to the stress of the convergence ○ Divergent  Shallow earthquakes at ridge  Crust above lithosphere above Asthenosphere  The more dense the crust, the older it is  Can temporarily have continental divergent boundaries ○ Transform  Plates slide horizontally past each other  Often connected by two mid-ocean ridges ○ Other facts  When two continental plates converge, neither one subducts □ It then collides and comes together with thick ridges  India and Asia i.e. Himalayas □ Thicker crust means no volcanoes  The colder (older) of two convergent plates subducts - Plate Motion ○ Most likely due to gravity with slab-pull and ridge-push

Convergent

Ch. 2 - Earth Materials Friday, September 1, 2017

9:23 PM

Chapter 3 - Minerals ○ Earth has ~5000 known minerals  `1500 undiscovered  2/3 minerals are linked to biological activity - Mineral Class ○ Carbonate dissolves in acid ○ Many metal resources come from Oxide and Sulfides - Silicate Tetrahedron ○ Made up of combinations of silicate tetrahedra  One silicon atom bonded with 4 oxygen atoms ○ Isolated tetrahedron  Bonded with other elements □ Olivine (Mg, Fe)2SiO4 ○ The structure of the mineral controls the mineral properties such as cleavage (how the mineral breaks) or fractures - Single Chains ○ Tetrahedra bond together to form chains with other elements between the chains  Pyroxene (NaCa)(Mg, Fe, Al)(Al, Si)2O6 ○ 2 directional breaks in the chain, 90 degrees - Double Chains ○ Single chains bond together to form double chains with other elements between the double chains  Amphibole ○ 2 directional breaks in the chain, 60 - 40 degrees, wider than single - Sheets ○ Tetrahedra bond together to form sheets with other elements between the sheets  Muscovite ○ 1 directional break between sheets  Mica peels off sheets, sheets are strong, bond between sheets isn't - 3D Frameworks ○ Tetrahedra bond together to form 3D structures  Quartz SiO2 - Mific V. Felsic ○ Mafic (ferromangnesian)  Contains Mg and/or Fe  Generaly dark in color ○ Felsic (non-ferromangnesian)  Do not contain Mg or Fe  Generally light in color

Part 2 - Molybdenum (Mo) ○ Used principally as an alloying agent in steel, cast iron, and superalloys to enhance hardenability, strength, toughness, and wear and corrosion resistance ○ Molybdenite - MoS2 - Gold (Au) ○ Estimated domestic uses were jewelry - 41% electrical and electronics ○ Deposited by high temperature hydrothermal fluids ○ Erosion, transport, and concentration ○ Same as formation of Silver deposits - Gypsum (CaSO4H20) ○ Used mainly to manufacture wallboard and plaster products. Also used in cement production and as fertilizer ○ Found in sedimentary evaporate deposits

Ch. 3 - Igneous Environments Tuesday, September 12, 2017

3:21 PM

- Igneous rocks are formed from the cooling of molten rock - Igneous rocks are classified by their composition and texture - Extrusive rocks ○ Extrusive igneous rocks cool quickly and as a result these rocks are fine grained or has lack of crystal growth ○ Small crystals in certain areas due to rapid cooling - Intrusive rocks ○ Intrusive igneous rocks are from magma that cools slowly and as a result these rocks are course grained ○ Can see crystals throughout the majority of the rock

- Identify ○ Granite ○ Diorite ○ Gabbro ○ Rhyolite ○ Andesite ○ Basalt - Textures ○ Pegmatite  Very large crystals

○ Phaneritic  Coarsely crystalline ○ Porphyritic  Large crystals surrounded by very small crystals ○ Aphanitic  Finely crystalline - Slower cooling = Larger crystals - Melting rocks by ○ Adding temperature ○ Lowering pressure ○ Adding water

Mafic rocks melt at a higher temperature than felsic rocks Get felsic magma from melting continental crust Get mafic magma from melting mantle Get intermediate from melting both/between Mafic magma - 50% silicon Felsic magma - 75% silicon Continental divergence ○ Driven my decompression and heating - Ocean divergence ○ Driven by decompression - Ocean-Continental convergence ○ Driven by heating and addition of water -

Ch. 4 - Volcanoes Thursday, September 21, 2017

3:25 PM

- Eruption Types ○ Mafic eruptions  Viscosity: Low (very runny)  Gas content: Low  Explosiveness: Low  Debris: Low  Form: Shield volcano (shallow dome like)  Setting: Oceanic hot spot (e.x. Hawaii) ○ Intermediate eruptions  Viscosity: Medium  Gas content: Medium  Explosiveness: Medium  Debris: Medium  Form: Composite volcano (Steep slope, volcanic rock and ash)  Setting: Volcanic arc (convergent plate boundaries) ○ Felsic eruptions  Viscosity: High  Gas content: High  Explosiveness: High  Debris: High  Form: Dome/caldera  Setting: Continental hotspot (e.x. Yellowstone) - Potential Volcanic Hazards ○ Lahar - a type of mudflow/debris flow composed of pyroclastic material, rocky debris, and water ○ Ash fall ○ Pyroclastic flow - a fast-moving current of hot gas and volcanic matter moving up to 450 mi/hr - Determining how dangerous a volcano is ○ Mafic/Intermediate/Felsic ○ Earthquakes = becoming active ○ History ○ Tectonic activity ○ Temperature of the surface ○ Shape ○ Age - Monitor Volcanoes ○ Gas ○ Deformation ○ GPS ○ Surveying ○ Remote sensing ○ Thermal imaging ○ Satellite ○ Cameras ○ Earthquake sensor ○ Lahar sensor

○ Ground vibration

Ch. 5 - Sedimentary Rocks and Environments Tuesday, September 26, 2017

3:37 PM

- Overview ○ Sedimentary rocks are made from the products of chemical and physical weathering, i.e. the breakdown of other rocks ○ Sedimentary rocks are classified according to what they are made of and what their textures are ○ Sedimentary rocks record information about the environment in which they are formed - Process of making sedimentary rocks

- Physical weathering ○ Fracturing ○ Frost and mineral wedging ○ Roots and other biological activity - Chemical weathering ○ Dissolution ○ Hydrolysis ○ Oxidation ○ Biological reactions - Bowen's reaction series

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○ Feldspar weathers by hydrolysis to clay minerals ○ Clay minerals accumulate in soil or muddy environments ○ Mafic minerals from clay minerals or oxidize to hematite ○ Quartz is hard some weathers to quartz grains Types of Sedimentary rocks ○ Clastic  Make from pieces (clasts) of rock ○ Chemical  Made from dissolved ions precipitated through chemical reaction  Crystals grown together ○ Biochemical  Made from dissolved ions (and other materials) by living organisms  Crystals grown together Clast sizes ○ Boulders ○ Cobble ○ Pebbles ○ Sand ○ Silt ○ Clay Indicators of Environment ○ Color of rocks ○ Size, shape, sorting ○ Thickness of bedding ○ Type of bedding ○ Fossils ○ Mud cracks Grain Sizes ○ Larger grain sizes  Greater energy in environment ○ Smaller grain sizes  Smaller energy in environment

- Clastic characteristics of breccia ○ Rocky mix ○ Muddy mix ○ Near steep mountain ○ Debris flow

- Clastic characteristics of conglomerate ○ River channel ○ Alluvial plain ○ Beach

- Reconstruction with ocean and land ○ Sea moving in is transgression  Sandstone, Mudstone Limestone (bottom up) ○ Sea moving out is regression  Limestone, Mudstone, Sandstone (bottom up)

Ch. 6 - Metamorphism and Deformation Tuesday, October 3, 2017

3:22 PM

- Stress: a force acting on a rock per unit area ○ Three types of stress:  Compression  Tension  Shear ○ Stress can cause strain, if it is sufficient to overcome the strength of the object that is under stress - Strain: a change in shape or size resulting from applied forces (deformation) ○ Rocks only strain when placed under stress ○ Any rock can be strained ○ Strain can be:  Elastic  Brittle  Ductile - Structures: deformation features that result from permanent (brittle or ductile) strain

- Normal fault is tension because as the wall falls, the rock is expanding in a way

- As a parent rock goes under a change in temperature and pressure (degree of metamorphism), it becomes a metamorphic rock ○ Undergo both physical and chemical changing ○ Physical  Deformation  Rotation  Shearing ○ Chemical  Recrystallization  Pressure solution  Remobilization - Foliation: Result of Ductile Deformation

- Isostasy: the equilibrium that exists between parts of the Earth's crust, like blocks floating on the underlying mantle ○ Increase in block height increases elevation ○ Increase in block density decreases elevation ○ Increase in liquid density increases elevation ○ Heat will increase elevation - Controls on Regional Elevation ○ Regions with thick crust are high ○ Regions underlain by less dense crust are high ○ Warm rocks are less dense, so warm regions are higher than cool ones - Ways to Increase Regional Elevation ○ Shorten/thicken crust ○ Add surface material ○ Add magma at depth

○ Heat crust or mantle - Ways to Decrease Regional Elevation ○ Structurally thin crust ○ Erode material ○ Cool crust or mantle - How Faulting Can Form Mountains ○ Thrust faulting ○ Normal faulting How Rocky Mountains were formed ○ Igneous and Metamorphic rocks are located at high elevations ○ These rocks became uplifted relative to the surrounding rocks through reverse fault ○ Generally thicker beneath the Rockies ○ Compression stress to cause the reverse fault ○ Continental Collision or Subduction could have caused the growth ○ Formed from shallow subduction

Ch. 7 - Geologic Time Tuesday, October 10, 2017

3:22 PM

- The Earth is 4.6 billion years old - Principle of Original Horizontality ○ Sedimentary rocks are assumed to have been deposited in horizontal layers, if they are no longer horizontal, that deformation must have happened after the rocks were formed

- Principal of Inclusion ○ If inclusion (or clasts) are found in a formation, then the inclusion must be older than the formation that contains them

- Principle of Cross-cutting Relationships ○ The geologic feature which cuts another is the younger of the two features

- Principle of chilled or baked margins ○ When a hot magma intrudes into cold country rock, the magma along the margins of the intrusion will cool more rapidly than the interior ○ When magma comes in contact with soil or cold rock, it may cause the soil or rock to heat up resulting in a baked zone in the surrounding rock near the contacts with the igneous rock

- Development of Unconformities: ○ Angular unconformity: boundary between tilted layered rocks and horizontal layered rocks

○ Nonconformity: boundary between non-layered igneous or metamorphic rocks and layered sedimentary rocks

○ Disconformity: boundary between two sedimentary rocks where erosion has occurred or there was a period of no deposition

- Fossil Succession ○ 3 concepts are important in the study and use of fossils  Fossils represent the remains of once-living organisms  Most fossils are the remains of extinct organisms; that is, they belong to species that are no longer living anywhere on Earth  The kinds of fossils found in rocks of different ages differed because life on Earth has changed through time - Radioactive Decay ○ Isotope: same element, different number of neutrons ○ Radioactive Decay: spontaneous change in the nucleus of an atom releasing matter or energy ○ Half-life: the lifetime of half the radioactive isotopes in a system

○ Half-life works on minerals through time

- Age of a rock ○ Age of rock = (# of half-lives that have past) * (length of half-life)  E.g. 1,408 million years = (2 half-lives (started with 20,000 atoms of U-235 and now have 5,000)) * (704 million years)

Ch. 8 - Earthquakes Thursday, October 19, 2017

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3:09 PM

Earthquake: the release of energy that occurs when there is sudden movement on a fault Focus (Hypocenter): location in the Earth where the earthquake starts Epicenter: location on the surface above the focus Amount of stress on a fault is highest just before an earthquake Body Waves ○ Travel through the Earth ○ P-wave: Fastest waves, travel through compression, particles move back and forth in same direction as propagation ○ S-wave: Slower than p-waves, particles move up and down in propagation direction Surface Waves (dissipate as moving down crust) ○ Travel along the surface of the Earth ○ Love wave: Move left and right from propagation direction ○ Rayleigh wave: Move in circular path in propagation direction Seismic waves travel out in all directions from the focus of the earthquake, and are recorded by seismometers Locate earthquakes 1. Measure time in between P and S wave arrivals 2. Use time to determine distance 3. Triangulate location using least 3 stations How to measure earthquake size ○ Richter Magnitude is based on the amplitude of S-waves Moment Magnitude: measure of the amount of energy released during an earthquake

- Earthquake intensity

- USGS National Earthquake Information Center - Golden, CO - Liquification: Loose sand and silt that is saturated with water can behave like a liquid when shaken by an earthquake

Ch. 9 - Rivers and Flooding Thursday, October 19, 2017

3:40 PM

- Drainage basin (watershed): Area of land that drains all of the streams and rainfall to a common outlet such as the outflow of a reservoir ○ Ridges and hills that separate two watersheds are called the drainage divide - Our hometown watersheds: Cache La Poudre River, South Platte River, Missouri River, Mississippi River - Acre-foot: 1 acre-foot = 325,900 gallons = enough for 2 family homes of 4 for 1 year - How rivers form/behave ○ Sediment balance in a river  Removal/Build-up of sediment  Particle size  Amount added  Stream slope  Flow ○ Stream slope/gradient = change in elevation/distance - Stream flow (Discharge): Volume of water that is flowing through the river ○ Discharge (m3/s) = Width*Depth*Velocity - Sediments in Rivers ○ Depending on speeds, grains/sand will flow down river

- Front Range Flooding Case Histories ○ Flash floods: Water rises rapidly with little warning  Stem from unusually intense rainfall or dam failures  Typified by a rapidly moving wall of debris-laden water ○ 1997 Spring Creek Flood, Fort Collins, CO  Flash flood morning of July 28, 1997  Five people died  Millions of dollars of damage to people's homes, roads, bridges, CSU campus ○ Big Thompson  Flash flood, July 1976  Intense summer convective thunderstorm  Approximately 19cm (7.5 inches) of rain in one hour, up to 12 inches over several hours

 Turbulent water reached velocities of 8m/s (26.3 ft/s)  Killed 144 people, washed away hundreds of homes, businesses  Discharge 884 m3/s (31,200 ft3/s  Message: climb to higher ground, get out of cars - Living with floods ○ People living in floodplains face hard choices  Move or expect eventual catastrophic loss ○ Land use changes may mitigate flood damage  Establish floodways - places designed to transmit floods  Remove people and structures from these places ○ Flood risks are borne by homeowners, insurance companies, lenders, and government agencies ○ Hydrologic data are used to produce flood risk maps ○ Maps allow regulatory agencies to manage risks ○ Building in flood-prone settings is tightly regulated - Flooding probability ○ Probability that a flood will occur  P=1/RI  RI = recurrence interval (average number of years between successive floods of a given size)

Ch. 10 - Groundwater and Water Resources Thursday, October 19, 2017

3:40 PM

- 1% of all water on Earth is fresh water

- Aquifer: a body of saturated rock through which water can easily move ○ Unconfined Aquifers: open to surface ○ Confined Aquifers: beneath low permeability layers

- Groundwater flows from areas where the water table is higher to where it is lower ○ Groundwater movement is slow relative to surface water ○ It must percolate through pore openings ○ Flow is further slowed by friction and electrostatic forces ○ Typical rates of flow:  Ocean currents: 3 km/hour

 Steep river channel: 30 km/hour  Groundwater: 0.00002 km/hour - Increase in permeability to increase rate of groundwater flow - Increase the flow of water table to increase rate of groundwater flow - Water table is a surface, shown as a elevation contour map ○ Flow is perpendicular to contours ○ From high water table elevation to low water table elevation

- 2010 total water withdrawals = 355,000 million gallons per day - We use more surface water than groundwater - Water in Fort Collins comes from ○ Cache la Poudre River ○ Horsetooth Reservoir - Colorado Big Thompson Project ○ Splits the incoming water 50/50

Ch. 11 - Global Climate Thursday, October 19, 2017

3:41 PM

- Heat energy transferred through ○ Conduction: Through material to material ○ Convection: Through water ○ Radiation: heat waves - Earth's Energy budget ○ Shortwave radiation: incoming sunlight ○ Longwave radiation: outgoing heat ○ Change in Earth's Temperature = Incoming radiation - Outgoing radiation  If Incoming Radiation = Incoming Radiation, then Temperature is stable  If Incoming Radiation > Outgoing Radiation, then Temperature increases  If Incoming Radiation < Outgoing Radiation, then Temperature decreases

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About 30% of the incoming solar radiation is reflected by the clouds and Earth's surface, reflectivity is called albedo

- Climate Forcing: an imposed perturbation (change) of Earth's energy balance - Feedback: a factor that intensifies or weakens the original forcing ○ Positive feedback: reinforces initial change ○ Negative feedback: counteracts initial change - Regional Climate: movement of heat by air and water - The Coriolis effect: deflection of matter due to Earth's rotation - Archives of Past Climate Information (Proxies) ○ Tree ring width can be sensitive to temperature and/or water availability ○ Annual growth (like tree-rings) ○ Chemistry (oxygen isoltopes, Sr/Ca) dependent on temperature ○ Bubbles trap past air (CO2, methane) ○ Fossil Pollen ○ Fossil abundances ○ Fossil chemistry ○ Rock Type  Environment, Sea level ○ Fossil chemistry - Oxygen Isotopes ○ Lighter isotope likes to be in more mobile phase (gas vs. liquid vs. solid)

○ More evaporation = higher (above) ○ More precipitation = lower (above) - Oxygen isotopes measured in the shells of fossil foraminifera or other organisms that make calcite shells ○ Higher 18O/16O ratio = colder and more...