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Geo 1300 Final Notes.pdf

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Department
Geography
Course
GEOG 1300
Professor
Katelyn Congreves
Semester
Fall

Description
Weather: the short term condition of the atmosphere. Temperature, air pressure relative humidity, wind speed and direction, daylength and sun angle are important elements that contribute to weather 4 Air Mass Categories (5 MC ON WEATHER IN GENERAL) 1. Arctic: very cold 2. Polar: take shape at 90 degrees latitude (both N and S), cold 3. Equatorial: warm 4. Tropical: form in low latitude areas, moderately warm ▯ - air masses affect temperature, humidity and stability Classification Options - (humidity factor: C for continental, M for maritime) - other letter defines latitude E - equatorial A - arctic mT - maritime tropical cT - continental tropical mP - maritime polar cP - continental polar Life Cycle of a Midlatitude Cyclone - cyclogenesis: fronts meet, warm air pushed over cold air, warm air moves north on east side of low pressure area, cold air mass moves south, causes a rotation - occluded stage: cold air mass moves faster and pinches the warm air - dissolving stage: uplift of warm air over cold air is cut off - Characteristics Of Cyclone - frontal lifting: circulation draws in air, warm air forced up over cold air - low surface pressure at center, “eye of the storm” - converging surface wind: warm air moves N, cold air moves S - Movements - storm tracks: typical movements where cyclones commonly occur - generally flow in prevailing winds east to west (Westerlies) curve prominently poleward into midlatitudes - SO: usually moving towards the poles Thunderstorms - formed in 3 stages: - 1) cumulus stage: low pressure system, convergence and rising air - 2) mature stage: air moves up, eventually hits tropopause and can’t rise anymore, updraft turns into downdraft moving towards surface - 3) dissipating stage: most of the air is so dense that there is no longer an updraft, only a downdraft Tornados - 2 layers of wind (strong and weak) cause air drafts to rotate along a horizontal axis - low pressure updraft forms along axis, once updraft is strong enough it pulls up the spinning air draft - now have a vertical spinning air draft ▯ - measured on Fujita Scale: 5 Levels Tropical Storms - tropical storms have winds just under 119km/h - if higher, it’s either a hurricane (atlantic), typhoon (indian ocean, australia) or cyclone (pacific) --------------------------------------------------------------------------------------------------------------------- Hydrologic Cycle (4 MC & 1 SA ON FLUVIAL SYSTEMS) - describes the transfer of water among the atmosphere, lakes and streams, glaciers, soil, subsurface, plants and animals and oceans - involves water in 3 states (liquid, solid, gas) - can refer to fresh, brackish or salt water Surface Water - either a) flows over land or b) soaks into soil - percolation: water moving deeper into the soil Soil Water Balance Equation: Moisture Supply = Actual Moisture Demand + Moisture Surplus +/- Moisture Savings ▯ - expressed in units of length (e.g. mm) ▯ - assumes to have evenly fallen over area ▯ - rain gauges collect precipitation at the surface - basically, water inputs = the outputs +/- changes in water stores ▯ Question: If you collected 50 mm in a rain gauge at your house in Guelph over 1 day how many mm of rain fell over the city of Guelph over 1 day? ▯ Answer: 50 mm ▯ ▯ -> rain is spread the same in the specific area What is the volume of water which fell on the city? : r e w s n ▯ A 50mm x 86km2 = 4300m3 Soil and Water Terminology - Infiltration: water seeping downward into the soil - Percolation: water moving downward through the soil or porous rock in the subsurface environment - Throughflow: the lateral movement of water through the upper soil horizons - most water reaches rivers by throughflow - important for base-flow, storm-flow and generating saturation-excess overland flow - Runoff: when the soil is infiltrated to full capacity and excess water flows over the land Evapotranspiration Pattern: - more evapotranspiration in the South (warm temperature, closer to tropics) - during summer, evapotranspiration is greater than precipitation --> water deficit - during spring/fall, precipitation is greater than evapotranspiration --> water surplus 3 Types of Soil Moisture 1. Hygroscopic H2O - inaccessible to plants, thin layer tightly bound to soil particles via hydrogen bond - wilting point: only inaccessible water remains, plants wilt and die 2. Capillary H2O - accessible to plant roots, held against gravity in soil by hydrogen bonds - water moves downward in large pores between soil particles 3. Gravitational H2O - when soil becomes saturated after a precipitation event - percolated from shallow capillary zone to the deeper groundwater zone Groundwater - water in the saturated zone below the water table (lies beneath surface, beyond the soil moisture root zone) - to measure: drill holes to measure water table and porosity - over-pumping: an overuse of groundwater (occurs in Waterloo) - aquifer: rock layer permeable to groundwater flow, adequate for wells and springs - aquiclude: rock that can not conduct water in useable amounts 2 Types of Aquifers 1. Confined Aquifer - bounded above and below by impermeable layers of rock or sediment - water level rises due to the pressure of its own weight ---- but can be contaminated at the beginning of the confined aquifer 2. Unconfined Aquifer (aka water table) - impermeable layer below and above it, water flows freely but requires pumping - can be contaminated (would occur in the zone of aeration which then leads down to the water table) Groundwater and Baseflow - baseflow: the “normal” level of a stream between events of greater discharge (i.e. storm flow) - primarily composed of water discharged to stream from deeper groundwater and throughflow Pumping Groundwater - pumping of groundwater can create cones of depression - two wells: a shallower one with little use, and a deeper one that pumps more water - the cone of depression from the second well eventually causes the first well to go dry Groundwater and Streams: 2 Sets of Conditions 1. Effluent Conditions: - high water table, low stream - usually in humid regions 2. Influent Conditions: - low water table, high stream - usually in drier regions Discharge Hydrograph - precipitation causes flow of river to increase (more water) - discharge also rises rapidly due to surface runoff and peaks after rainfall event - storm flow: largely composed of surface flow and throughflow - receding flow: the discharge that falls at a slower rate due to baseflow Pre-Urban Hydrograph - low peak= low runoff volume - receding flow; infiltration continues to percolate, greater through flow Urban Hydrograph - increased peak flow and runoff volume; short flow duration - precipitation not infiltrating due to imperious surfaces Excess Overland Flow Step 1) Infiltration (very fast) - water enters a soil system faster than the soil can absorb/move it - precipitation exceeds infiltration capacity of the soil Step 2) Saturation (very fast) - soil becomes saturated and any additional precipitation or integration causes runoff 4 Types of Flow 1) Matrix Flow: flow of water through very fine pores (slow) 2) Macropore Flow: flow of water through larger pores (medium speed) 3) Pipe Flow: flow of water through larger cavities (soil pipes) that bypass soil matrix (fast) - can provide rapid connectivity, common in arid and semi-arid areas and in peat soils 4) Groundwater Flow: water that flows below the water table - soil or rock (aquifers, aquitards), saturated flow and can be modelled using Darcy’s Law Darcy's Law - Darcy's law (conservation of momentum) and the continuity equation (conservation of mass) are used to derive the groundwater flow equation Q = A(KI) - Q = volumetric flow rate (or discharge) --> how much water flows - A= cross sectional area - K=hydraulic conductivity - I= pressure difference (height difference) Catchment, Drainage Basin, or Watershed - an area of land which drains into a particular stream - open system, its boundary is the drainage divide - efficiency of water removal depends on proportion of hill slope area to channel density - runoff pathways in a catchment strongly affect the potential for downstream flooding - most water reaches channels via hill slopes - flow paths determine water quality and timing of delivery to outlet - they’re controlled by climate, topography, soils, vegetation, and land use -------------------------------------------------------------------------------------------------------------------- Climate - climate is weather over time - climate regions = areas with similar weather statistics - similar temperatures, precipitation, air pressures and air mass patterns 6 Climate Classifications (ONLY ONE MULTIPLE CHOICE ON THIS) 1. tropical 2. mesothermal 3. microthermal 4. polar 5. highland 6. dry --> Canada has 5/6 classifications (does not have any tropics) Earths Structure and Internal Energy (3 MULTIPLE CHOICE ON EARTH, 1 SA) - Core - 1/3 of Earth’s mass, mostly made of iron - generates Earths magnetic field via electrical currents flowing in the liquid outer core - Mantle - zone of discontinuity, 80% of Earths volume, made of oxides of iron, magnesium and silicates Endogenic vs Exogenic Processes - Endogenic: the system internal to Earth, driven by radioactive heat derived from sources within the planet. In response, surface fractures, mountain building, earthquakes and volcanoes occur - Exogenic: the system external to Earth, powered by insolation which energizes the air, water and ice and sets them in motion under the influence of gravity. Includes all processes of landmass denudation Continental vs Ocean Crusts - Continental Crust: less dense than oceanic crust (continents are at a higher elevation than the ocean floor), mostly made of granite - Oceanic Crust: less dense than mantle but more dense than continental crust, mostly made of basalt - Isostatic Adjustment: The movement of the solid part of the earth until it is in balance. The prime example of isostatic adjustment is the continents “floating” on the denser parts of the crust The Rock Cycle 1) Igneous Rock: forms and is formed by magma or lava - subduction of oceanic plates return igneous rock to the mantle to become magma - however, after a long period of time magma or lava rises to the Earths surface and solidifies into back igneous rock - from there, erosion from running water/wind breaks igneous rock into sediment 2) Sedimentary Rock - layers of sediment build up until the weight of the layers press the sediment together, then minerals glue the layers together - forming sedimentary rock - it can either melt into magma and lava OR form metamorphic rock 3) Metamorphic Rock - metamorphic rock forms when heat and pressure transform igneous and sedimentary rocks - it can either melt into magma and lava OR break into sediment --------------------------------------------------------------------------------------------------------------------- Pangea (5 MC & 1 SA ON PLATES, EARTHQUAKES, MOUNTAINS, VOLCANOES) - when all continents were one mega-continent - now have 14 plates that have broken from this mega continent - also meant there was one huge ocean - most plates include both continental and oceanic lithosphere - 200 mya Pangea began moving apart - broke into 2 continents: Laurasia in the north and Gondwana in the South Plate Boundaries - Divergent boundaries: - 2 plates moving away from each other - there is an upwelling of magma and molten material, mountain ridge/dome is created - Convergent Boundary: - 2 plates (one more dense than the other) - the more dense plate is sliding underneath, creates volcanic and earthquake activity, also deep trenches can form - Transform Boundary: - 2 plates sliding along each other at right angles to the sea floor spreading center, little disturbance, no volcanic or earthquake activity Three Crustal Orders of Relief 1. Coarsest Level of Landforms - continents and oceans 2. Intermediate Level of Landforms - continents and lowlands - mountain masses (e.g. Himalayas), plains, lowlands 3. Small and Detailed Level of Landforms ▯ - individual mountains, cliffs, valleys, hills Earth’s Hypsometry - earths diameter vs width (Earth is much wider than it is deep) 3 Types of Crust Formation - 1. residual mountains and stable cratons (ancient and inactive mountain areas) - all continents have a crystalline ancient rock (craton) aka the nucleus - a continental shield (e.g. Canadian Shield) is an exposed craton - 2. tectonic mountains and landforms (active, folding and faulting) - upwelling of material (basaltic magma) eventually goes underneath another plate, remelts, undergoes subduction and forms a mountain - 3. volcanic features (surface accumulation of molten rock from eruptions) - Terranes: bits and pieces of a continental plate that originally came from a different continental plate - e.g. Wrangell Mountains in Alaska originally came from the equator Crustal Deformation Processes (Stress and Strain) Stress and Strain - stress: the pressure applied to the crust - strain: how the crust responds to that pressure (will fold or fault/crack) a) Tension: pulling on either side of a crust, results in a stretched strain (a thinning crust on the surface) b) Compression: pushing on either side of a crust, results in shortening (a folding, hill and valley on the surface) sometimes too much strain can cause a reverse fault c) Shear: pushing on diagonal corners so it’s being twisted laterally Folding - anticline: on a ridge of a slope, land slopes downwards away from the axis - syncline: an axis is the trough 3 Different Types of Fault 1. Normal Fault - caused by tensional stress, pressure moving on either side of a center - eventually the stress becomes too great and an earthquake occurs - an escarpment is usually formed by this process 2. Reverse Fault - the land cracks under the compressional stress - could be convergent plates, portion of the land moves upwards 3. Strike-Slip Fault - shearing, right lateral or left lateral are formed by this force - linear rift created along the landscape (e.g. San Andreas Fault) Orogenesis (Mountain Building) Oceanic plate – Continental plate collision - formed at continental area - molten rock, uplifted, magma, folded layers of sedimentary rock - thermal process - e.g. Andes Mountains Oceanic plate – Oceanic plate collision - mountain formation after subduction zone - thermal process - e.g. New Herbies Trench Continental plate – Continental plate collision - no subduction, just 2 plates crushing - folded crusts/layers - mechanical process - e.g. Himalayan Mountains Earthquake Components - focus= subsurface area - epicenter= location on surface directly above the focus - shockwave = measured by seismograph - fault break= earthquake - aftershock= slightly less intense shock after initial shockwave - fault line: a lot of stress gets to yield strength then it develops into cracking VolcanicFeatures - hotspot tracks: where upwelling occurs, 50-100 sites around the globe, internal heat being released = geothermal activity - volcanoes form at the end of a central vent from asthenosphere and upper mantle - crater = circular depression near summit - lava (molten rock) gasses and pyroclastic (pulverized rock) eruption occurs - Hawaiian Basaltic Lava - rough, sharp edge rock; have golden strands which are natural glass - Pahoehoe= rope like strands 3 Volcanic Settings 1. subduction bounds: collision of plates, diverging ▯ -> mountains form 2. spread along sea floor ▯ -> crusts move away from each other and magma uplifts from the cracks 3. upwelling hotspot area ▯ -> Hawaii - Shield volcano: if you look at the horizon; slightly sloped - Composite volcano: if you look at the horizon; steep slope - composite volcanoes formed from explosive eruptions while shield volcanoes are formed gently ------------------------------------------------------------------------------------------------------------------- Denudation (5 MC & 1 SA ON WEATHERING, MASS WASTING, KARST) - any process which wears away landforms, primarily exogenic processes - Weathering: rock is disintegrated and dissolved - Mass movement: unit movements of materials propelled by gravity - Erosion: removal of surface material by wind, water or glaciers - Transportation: transport of material - Deposition: process by which transported sediments are laid down - Gradation: same as degradation, smooth out the earths surface, only relevant above sea level - Tectonic disturbance: tectonic uplift Parts of A Slope - waxing slope: increasing, convex part of slope - free face: cut-off or cliff - debris slope: transportation of materials from cliff - waning slope: concave part of slope Forces Acting on Slope - the weight of the rock acts through the center of mass - normal force is always at right angles to the surface - geomorphic threshold = the rock wants to slide downwards - frictional resistance: resisting geomorphic threshold - weight force is resolved into 2 components: - perpendicular to plane - parallel to plane Regolith, Soil and Parent Materials - regolith: unconsolidated material, loose surface subjected to weathering - parent material: consolidated bedrock - e.g. sand is regolith and grand canyon is parent material, sand is a result of the parent material decomposing Types of Weathering Processes - physical: mechanical breakdown of rock - chemical: rock breaks down due to chemical reactions - biological: could be linked to physical and chemical, but mostly facilitated by organisms ---> usually multiple occur simultaneously, look at annual rainfall and mean annual temperature to determine which factors are more present Physical Weathering - breakdown of rock due to mechanical forces, internal and external stress and pressure - Type A: Thermoclasty - temperature change and shock, rapid stress, fatigue-failure - Type B: Freeze- Thaw - water enters cracks in the rocks and freezes, therefore expanding in volume - creates “joint-block separation” - Type C: Shattering - when rock hits the ground, intensity can cause the rock to break - Type D: Salt Weathering - formation of salt crystals, sometimes called “salt wedging” - water evaporates leaving salt, often seen in sandstone - dilation = pressure release - physical expansion of rock - unloading and exfoliation Water - water is often a reagent and a transportation medium - effective solvent - its chemical and physical properties influence environment - Differential Weathering - different rock masses or sections may break down at different rates - hard materials + recent uplift = high relief mountains - soft rock material + tectonic inactivity = low relief, low elevation - Physical-Biological Weathering - when tree roots grow through rocks and split them apart - tensile stress generated by fungi in micro-cracks - expansion of fungi and lichens through hydration Chemical Weathering - water usually present - products are less resistant to breakdown, greater in volume (expansion of fractures in rock), dissolved particles - Type A: Spheroidal Weathering - rocks are spheres, caused by chemical reactions - hydration: combination of H20 and another molecule - hydrolysis: carbonic acid and water = residual clays - oxidation: iron and oxygen = rust, can occur in soil - carbonation: calcium carbonate + carbonic acid and water = calcium bicarbonate - Chemical-Biological Weathering - organisms produce CO2, enhance carbonation - can lead to soil acidification, bacteria living on rock surfaces - lichens can be linked to a range of chemical and physical weathering processes Mass Movements (Landslides) - the downslope movement of material (bedrock, regolith or a mixture of both), commonly referred to as a “landslide” - slope failures: a sudden failure of the slope resulting in transport of debris down hill by sliding, rolling - sediment flows: debris flows downhill mixed with water or air 3 Types of Sediment - loose, unconsolidated material - 1. clastic sediments - 2. biological sediments - 3. chemical sediments - sedimentation: the process by which sediments are deposited leading to accumulation - till: glacially deposited sediments - alluvium: deposited by water in a non-marine setting (fluvial) - colluvium: deposited at the base of hillslopes - lacustrine: deposited in lakes 4 Types of Mass Movements 1. Falls 2. Slides or Slumps ▯ soil isn’t saturated with moisture, but its not dry either - a sudden rapid movement of a cohesive mass of regolith or bedrock that’s not saturated with moisture 3. Flows: wet conditions - Earthflow: flows that have more moisture than slides, often triggered by heavy rainfall - Mudflow: highly fluid, result of heavy rains over gently sloping stream beds 4. Creeps: dry conditions ▯ - creep: caused by frequent freeze-thaw cycles - when exposed to freezing the water inside it expands, called “frost heaving” - subsidence occurs as frost melts - causes rocks to lift during expansion, and fall after thaw Debris Avalanche - Rockfall: a volume of rock that falls through the air and hits a surface - the resulting debris are irregularly shaped and often become part of talus cones Solifluction - common in permafrost when top layer of the soil thaws - can cause downslope movement even over very gentle slopes Protecting Against Hazards of Mass Movements - install tile drains, ditches and pumped wells to ensure the slope doesn’t become saturated, reduce slope angle - reinforce slopes withs steel rods and netting, build retaining walls - restrict development on the top of vulnerable slopes Karst Topography - Karst topography: a geological formation shaped by the dissolution of layers of soluble bedrock, usually carbonate-based rock such as limestone or dolomite, but also in gypsum - happens after sedimentary sock is exposed to weathering - karst formation is inhibited in flat areas, promoted when limestone is underneath ▯ - high relief = faster moving water and more erosion Things Needed for the Formation of Karst - 80+% calcium carbonate for dissolution via water - patterns of joints in otherwise impermeable limestone - aerated zone (i.e. Caves) - vegetation that may supply organic acids which enhance dissolution process - develops where soluble limestone is rich in calcite forms Carbonate Sediments: Major Components 1. Skeletal fragments of marine/freshwater organisms 2. Bioherms (e.g. reefs composed of CaCO3) 3. Non-biological components (precipitation of CaCO3) - most abundant in tropical/subtropical shallow marine environments - limestone is CaCO3 composed of the remains of shells of algae - Evaporites are the most important: result of minerals being precipitated from lake/ seawater, concentrated by evaporation - gypsum is the most common evaporite mineral - halite is more rare and requires greater evaporation - more common in arid environments Features and Types 1. Temperate Karst - forms relatively slowly - contains disappearing streams, solution depressions, cave networks - tropical karst develops more quickly than temperate karst because of the temperature range in tropical areas 2. Caribbean Karst: - flat areas/ underground springs (e.g. Florida and Mexico) 3. Karst Towers - tropical areas, cone-shaped - more resident bedrock 4. Disappearing Streams and Sinkholes - low lying places become solution holes - collapse sinkholes created when cave collapses Caves - form in limestone via carbonation - stalactites- limestone formations hanging from cracks in ceiling - stalagmites- limestone formations on the floor - columns = binding Urban Stone Decay - stone decay occurs through the dissolution of limestone by acid rain, salt weathering ▯ - salts can come from atmospheric pollutants (humans) - may also be a result of construction - spatial organization on ground decay quicker due to more contact with water which may be acidic - human interference may increase rapid surface loss, such as ▯ - humidity, rainfall, air pollution, de-icing, vibrations, human contact Stress History - “pre-emplacement” and “post-emplacement” effects - increases susceptibility to future decay no matter the atmospheric pollutants ----------
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