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GPHY 102 (winter 2014) - Condensed Exam Notes with Important Diagrams (31 pages)

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GPHY 102
Paul M Treitz

1 / 32 GEOGRAPHY 112 CONDENSED NOTES Chapter 1 Scales: 10^4=football field. 10^10=circumference of Earth. No bigger than earth.  Global: entire energy balance. Earth-Sun Relationships.  Continental: albedo, water, latitude, longitude, elevation; ocean and air currents.  Regional: sub-continental. cloud, weather and climate patterns. regional vegetation and soil.  Local: exact patterns of weather and climate, vegetation and species etc. more precise than regional. e.g. lake Ontario’s effect on Kingston’s weather; or little Cataraqui Creek.  Individual: one single sand-dune in a desert. Time Cycle: regular intervals in which flow rates in a system speed up-slow down. e.g. 365 days. Regional vs. Systematic: Regional: everything in the same place. Horizontal, comprehensive. Systematic: compare same thing everywhere. Vertical as well as horizontal. e.g. economic geography. systematic approach ranges from human geography (social economic behavioural) and natural sciences (atmospheric, terrestrial and marine). Spatial information: maps, spatial analysis, images—all numerical based. Tools in geography Information Science (portraying information on Earth’s surface) include: maps (cartography), Geographical Information Systems (GIS)—more easily up-to-date than maps, remote sensing (from aircraft/spacecraft), GPS, mathematical modeling. Physical Geography Focus on patterns and processes on earth’s surface. Pattern=expression, composition and structure (static) Process=behaviour, function and mechanisms (dynamic) Fields of physical geography: Meteorology: study of weather. Climatology: study of climate. Geomorphology: how landforms are created—which also involves oceanography and costal geography (erosion, etc) Geography of soils: distribution of different soil formations. Biogeography: distribution of organisms (biodiversity, ecology, etc) Also, in applied physical geography which lies between physical and human geography: water resources and hazard assessment. Flow systems: includes interconnections and flows of matter and energy. e.g. how does one component affect whole system? Flow systems include: 1) system components, 2)structure of pathways, 3) a power source. All material systems are closed if the scale is large enough. A closed material system is called a material 2 / 32 cycle. however, energy flow systems are always open (e.g. Earth-Sun). Only open systems have inputs and outputs. Positive feedback: reinforces the flow. Negative feedback: regulates/dampers the flow. Equilibrium: when flow rates in all passage ways remain constant. it is usually regulated by some negative feedback. e.g. lake in equilibrium: inflow and outflow balanced. Three realm/spheres: 1) atmosphere 2) lithosphere 3) hydrosphere 4) biosphere is the intersection of the former three. Frozen/ice portion of the hydrosphere is referred to as the cryosphere, which is very susceptible to climate changes, “canary in the coal mine” Global geographic concerns  climate change e.g. Carbon Cycle  Positive feedback. CO2 second most abundant. methane, NOx and Sox and CFs also count.  agricultural areas dislocated, desertification, rise in sea level, increased frequency of extreme events.  Kyoto Protocol: reduce CO2 emission by 20%  Biodiversity (leads to loss of pharmaceuticals)—natural defense mechanisms. e.g. bioactive conpounds that can fight human cancer.  diverse ecosystems respond better to environmental change.  Pollution Chapter 2 Earth is an ellipsoid. Earth rotates counter-clockwise. 24 hour rotation responsible for: measure of time, geographic grid, effect on earth processes and life, environmental effect, Coriolis effect. Time zones: 15 degrees per hour. Numbered by how far away from Prime meridian. Left is negative whereas Right is positive. (+12) tides: when moon, sun and earth all lined up, you get extreme tides. Intersection of parallels and meridians locate places. Parallels give measure of latitude; (N/S from equator) Meridians give measure of longitude (E/W from Prime Meridian in Greenwich, meet at 180 E/W or international date line). o Degrees: Historically: you divide a degree into 60 minutes, a minute into 60 seconds. (e.g. 53 33’33’’N). Now: decimal degrees are the standard. Great circles: pass through centre of earth, divides it in halves. Use this to find the shortest distance. GPS: works with a network of satellites that send radio signals to calculate position. 3 / 32 Map projections: requires distortion. Polar projection: plane. Parallels in concentric circles. more outward, more distortion. Mercator Projection (cylinder): cut off at 80 N/S because it extends to infinity toward poles. used for navigation because straight line on map represents rhombus line. Goodes Projection (mathematical curves): Earth divided into three chunks, parallels are straight lines. projects areas in correct sizes but distorts shapes. Revolution Around the Sun: Angle of axis 23.5 degrees from the line perpendicular to the plane of the ecliptic. This causes seasonal variations. Summer solstice (June), sun’s declination (ephemeris) directly above cancer (declination +23.5 means north); Winter solstice (Dec): declination above Capricorn (declination -23.5 mean south). Equinoxes (march and September): directly above equator. Patterns of daylight: Maximum in summer solstice, minimum in winter. Chapter 3 All electromagnetic waves have wavelength and frequency. Shortwave: primarily from the SUN. short wavelength, higher frequency, hot. includes ultraviolet (doesn’t penetrate atmosphere easily b/c of ozone) and visible light (penetrates easily), and new infrared and shortwave infrared. Longwave: primarily from the EARTH. longer than 3mms. includes middle infrared (from the sun) and longwave thermal infrared emitted by temperature bodies. Reflectance: vegetation reflects most green lights. Low reflectance=good absorber/black body, like water. Wavelength and temperature are inversely related; hot objects emit much more energy (short wave) than cool ones. Solar energy: emit most visible light. 4 / 32 Earth energy: emit most thermal infrared. atmosphere absorbs more infrared than visible lights. Insolation means incoming solar radiation, unit: W/m^2. Insolation depends on: 1) angle of the sun above horizon (greatest at 90) 2) length of exposure. Solar constant: 1367w/m^2 at 90 degrees. Global Energy Balance: energy coming in has to equal energy going out. Height of the sun and day length vary with altitude and time of year. Tilt of the earth redistributes large amounts of energy to polar regions. Compare: axis tilted and axis perpendicular. Calculate net radiation: net radiation=net shortwave radiation + net long wave radiation. net short wave=(shortwave coming down)-(shortwave going back up) net long wave=(longwave coming down)- (long wave going up) positive values represent energy going TOWARD surface. Energy deficit areas: negative net radiation; Energy surplus areas: positive net radiation. Deficit at the poles is compensated by surplus at equatorial regions through air and ocean currents. Insolation patterns divide latitudinal zones: equatorial, tropical, subtropical, midlatitude, subarctic, arctic, 5 / 32 polar. Only midlatitude has distinct seasons. Insolation in the atmosphere can be 1) absorbed 2) scattered 3) reflected. Blue sky is a result of scattering of blue wavelengths. Albedo of the earth is about 0.3 which means 1/3 of the light is reflected away. Global Energy System counter-radiation and greenhouse keeps temperature >0. More vapour and CO2 means more counter-radiation and greenhouse. Describe what’s happening here: Left: Shortwave Radiation Right: Longwave Radiation. Surface Gain (of both short and long wave) = Surface loss (of long wave, latent heat and sensible heat) note: if shortwave is directly reflected off the surface, it doesn’t count as surface loss. Surface LOSS means it was absorbed first. Two types of energy budgets: Surface Energy Budget (atmosphere and energy that hasn’t been absorbed by surface doesn’t count) Surface Gain: 49(R ) S 95(R ) =L144 units Surface Loss: 114(R ) L23(H ) +L7(H ) =S144 units Atmosphere Energy Budget Inputs: 20(R )S+ 102(R ) L 23(H ) +L7(H ) =S152 units Outputs: 57 (R ) L 95 (R ) L 152 units Chapter 4 Insolation varies with 1) latitude 2) slope and aspect 3) cloud cover 4) surface type 5) proximity to water 6) elevation. Net radiation determines surface air temperature, due to sensible heat transfer (from body to body) and latent heat transfer (chemical change of state). Latent heat transfer cannot be measured directly. Insolation and net radiation have similar daily patterns: high during day and low toward night. However, net radiation can be negative, whereas insolation is 0 at its lowest. Because of longer days in summer: 6 / 32 Daily net radiation is positive in summer and negative in winter. Daily insolation is greater in summer, within the same area. However, longer daylight doesn’t necessarily mean higher insolation. Density also matters (think poles). Air temperature peaks after insolation has peaked, because there is still heat in soil on surface. Lowest air temp: 1/2 hours after sunrise. Highest air temp: mid-afternoon (2-4pm) Temperature continues to fall into the night. Different layers of atmosphere: Troposphere: densest, lowest 20km, where weather occurs.. Temperature drops consistently until it hits tropopause. TROPOPAUSE Stratosphere: from tropopause, temperature consistently rises in stratosphere, because ozone layer on top absorbs most UV. Mesosphere: without ozone, temperature cools. MESOPAUSE (everything below mesopause is homosphere) Thermosphere: temperature warms rapidly in very thin atmosphere (heterosphere) Atmospheric Composition (up to 25,000 m) in Troposphere Gas Volume (%) N2 78.08 O2 20.85 H2O <1 to 4 Argon (Ar) 0.93 CO2 0.0360 Neon (Ne) 0.0018 Helium (He) 0.0005 CH4 0.00017 H2 0.00005 Nitrous oxide (N2O) 0.00003 exam question Ozone (O3) 0.000004 Troposphere contains water vapour and aerosols. It is the most expansive at the equator and most condensed at the poles. Tropopause tends to get higher during summer months due to heating. Environmental lapse rate: atmospheric temp drops 6.4C/km all the way up to tropopause. At higher elevations, thinner atmosphere allows for rapid warming during day and rapid cooling at night. Mean temperature decreases but daily temperature increases. Annually, higher latitudes have more drastic annual ranges in net radiation and temperature compared to the equator. 7 / 32 Penetration of radiation Heats and cools Mixing of layers Evaporation (which contributes to cooling) Land NO QUICKLY NO LESS Water YES SLOWLY YES MORE Land/inner area has more varied daily range and annual range in temperature Water/marine area has late maximums and late minimums because of slow response to insolation change. Finally: The greatest ranges occur in the sub-arctic and arctic zones of Asia and North America. The annual range is moderately large on land areas in tropical zone, because too much solar intensity, no water.. The annual range is smallest over oceans in the tropical zone, because solar intensity doesn’t change much over the year and water has moderating effect. Isotherms: A line drawn on a weather map or chart linking all points of equal or constant temperature. Chapter 5 Atmospheric pressure: the force per unit area exerted by the weight on a column of air (to the top of atmosphere). Unit: 1kPa=10mb Doesn’t decrease linearly as you go up, because atmosphere thins down—most of the stuff concentrated within 5km. Marked by isobars. Wind has DIRECTION and SPEED, happens because of atmospheric pressure gradients. flows from higher pressure to low pressure. Closer isobars=faster winds. Wind direction is determined by 1) gradient force 2) Coriolis force 3) friction Coriolis Force: deflected to the right in northern hemisphere. Deflection is bigger toward poles, because different latitudes have different linear speeds. Higher speed means greater deflection, this leads to the creation of jet streams. happen in upper air due to less friction Poles has more condensed air and closer pressure bars. So at a very high elevation, pressure difference between pole and lower altitude will be very great. This causes very fast winds to form. Each large meander, or wave, within the jet stream is known as a Rossby wave. They are undulations that develop at the polar front and create wave cyclones. 8 / 32 CONVECTION LOOP: 1) constant air pressure 2) X warms faster than A and B 3) hotter air rises up 4) replaced by colder air. Convection cells create: Sea breezes: breezes from the sea during the day because colder sea air pulled in; Land breezes: breezes from land during night because colder land air pulled toward sea. In Northern hemisphere: 1) Cyclone anticlockwise; 2) Anticyclones clockwise. Hadley cells: huge convection loop. Rises at equator, creates ITCZ and equatorial trough. Subsides at 20-40 N and S, creating subtropical highs, depends on seasonal tilt. Clockwise wind circulation around the highs (which are anticyclones) causes westerlies to flow from west and tradewinds to flow from east. 9 / 32 Subsiding air sits on top of cold ocean currents on west coast, forming trade-wind inversion. This makes west-coast dry and foggy in summer. Chinooks: Precipitation on windward side; cold air descends leeward and cools diabatically, dispersing downhill to lower pressure regions as warm winds; Mountain and Valley winds: Morning: great pressure differential between slope ground and air, strong upslope wind Midday: less pressure differences due to warming, wind slows down Night: air cools and sink down, downslope wind. Ocean temperature: Surface layer is warm due to insolation and heat in the atmosphere. THERMOCLINE Then: rest of 90% of water, temperature drops rapidly. Higher latitude = colder temperature. Ocean currents exchange warm and cold waters between poles and equator. Ocean currents are influenced by 1) prevailing surface winds 2) Coriolis. Equatorial currents are driven by the trade winds; Westwind drifts are driven by westerlies and move hot water toward poles. Ocean gyres (20-30 N/S) track the subtropical highs, which are big anticyclones. Equatorial countercurrents are driven by ITCZ (doldrums). Deep currents/conveyor belt: a thermocline circulation process in which evaporation causes surface layer to become denser and begin to sink, enhanced when it reaches higher latitudes. Then the water is brought back to surface by upswelling. Upswelling 1) brings back nutrients 2) brings down excess CO2 and stores it for 1500 years. El Nino: upswelling along Peruvian west coast shuts down, coast warms up, weakening trade winds. precipitation shifts east toward Peru, fucks up temperature. La Nina: Increased upswelling, strengthening of trade winds, cold water carried westward. Chapter 6 Water 1) stores heat and nutrients and carbon 2) precipitation 3) circulates heat Fresh water only takes up 2.8%. The largest reservoir of fresh water is in ice sheets and mountain glaciers. Ice sheets > ground water > freshwater lakes > saline lakes > soil water > atmosphere > streams Global water balance is a material cycle: P (land and lake) + E (land and lake) + P (ocean) + E (ocean) = 0 Specific humidity: actual H2O content g/kg Water vapour capacity: maximum H2O content at given temperature 10 / 32 Relative Humidity = Specific Humility/Water Vapour Capacity Relative Humidity varies through the day. That’s why you have morning dews. Dew point temperature: when relative humidity is 100%. Varies depends on water content. If too little water, dew point is likely below 0, called frost point. SVP (Saturation Vapour Pressure): how much does H2O add to air pressure when air is saturated. Adiabatic Process: heating/cooling due to pressure change. DryAdiabatic Rate: constant, works when there’s no change of state in H2O. 10C/1km. Saturated Adiabatic Rate: applies when air hits dew point temperature and is simultaneously rising and condensing. This is NOT constant because it’s affected by: 1) current temperature 2) Water content (dew point temperature) 3) latent heat transfer 4) air pressure (higher pressure means less adiabatic cooling) The altitude at which air starts to condense is the lifting condensation level. Clouds: Super-cool state: when cloud droplets remain liquid below zero. Two major classes of clouds: stratiform (flat) and cumuliform (tall). Cumulonimbus is responsible for thunderstorms. Precipitation: Cloud droplets form around condensation nuclei to up to 50-200um, then congregate and fall. 4 precipitation processes 1) Orographic lifting (pushed up mountain range by westerlies) 2) Convergent lifting (air converge at low pressure trough, displaces air upwards. This happens frequently with trade winds at ITCZ, accounting for its tumultuous weather) 3) Convectional lifting (warm air rises and cools) 4) Frontal Lifting (occlusion, etc) Atmospheric stability Stable: air parcel will return to original position after moving up and down Unstable: air parcel will continue to rise/fall Absolute instability happens when Environmental Lapse Rate is greater than Dry/Wet Adiabatic Rates. This will create massive cumulonimbus clouds. Chapter 7 Jet stream marks polar front, where clashes of moist tropic air and cold polar air happen. Air masses: large bodies of air that have a source region. They move because of pressure gradients and Coriolis force. Sources of air masses impacting NA: 11 / 32 Maritime equatorial  Maritime tropical  Maritime polar decreasing temperature and specific humidity; Continental tropical  Continental polar Continental arctic decreasing temperature and specific humidity. Fronts are boundaries between air masses, named by the invading air. Frontal lifting: the fourth precipitation process: Cold front causes shorter, faster, more aggressive precipitation that warm fronts. FromA to A’, half of the clouds we see are associated with cold fronts. Cumulonimbus clouds usually develop when warm air is unstable and continues to rise—resulting in heavy precipitation. When cold front catches up with warm front, OCCLUSION happens resulting in precipitation. Clouds only form in troposphere! Weather system: a recurring pattern of atmospheric circulation. For example, travelling cyclones and anticyclones. Wave cyclones: mid to high latitudes; weak disturbances to powerful storms; Formation: two large anticyclones at polar fronts, one colder and dryer than the other. Both are high-pressure cells, so low pressure trough between them develops into a low pressure center, forming a cyclone. Wave cyclone at open stage, occlusion at occluded stage, and finally system dissolves in dissolving stage. When polar air meets warmer air, precipitation occurs as snow, not rainfall. On Exam: Weather changes within wave cyclone: open stage (left) vs. occluded stage (right) Tropical cyclones: tropical to subtropical; mild disturbances to highly destructive hurricanes/typhoons 12 / 32 Formation: hurricanes=wind speed over 125 km/h. Develop 8 to 15 N/S; warmer sea surface temperature = more occurrences. Gain energy through release of latent heat of rising unstable air (27 degrees+). They build strength on ocean then dissipate on land. More unstable air lower pressure centre faster wind speed from surrounding air (devastating) Tornado: small cyclones caused by strong convectional activity. Global heat and moisture transport: Hadley cells move equatorial warm air poleward (until the subtropic jet streams); From midlatitudes, Rossby wave mechanism further moves warm air poleward; Trade winds move surface air from subtropics back toward equatorial regions. Chapters 8 and 10 Climate: average weather over long period of time, affected by 1) latitude and 2) coastal/continental location Factors affecting temperature and precipitation: Range: interior has larger range than coastal; high latitude has larger range than low latitude High temperature: low latitudes; High precipitation: warmer locations; mountain ranges (orographic lifting); coastal regions. Koppen system: 5 major divisions based on temperature and precipitation: 1) tropical 2) dry 3) warm 4) Snow 5) (figure 8A.1) Subdivisions based on finer temp, precip, and vegetation. Group I: Low-latitude Climates Group II: Mid-latitude Climates  Dry subtropical (deserts)  Moist subtropical (hot humid summers, mild winters)  Mediterranean (hot dry summers, rainy winters)  Marine west-coast (warm dry summers due to subtropical highs, cool winters with precipitation maximum) 13 / 32  Dry midlatitude (interior rain-shadow regions; cP block out maritime in winter; dry continental dominates in summer with occasional mT invasion. Warm to hot summer, cold winter, low annual precipitation)  Moist Continental (cold winter, warm summer, polar front precipitation strong in summer when mT invades; winters dominated by cP and cA) Group III: High latitude Climates northern subarctic and arctic zones, all the way to 47 N. Climates coincide with westerly wind, interaction between mP, cP, and cA, creating cyclonic activity.  Boreal Forest Climate  Tundra Climate Lake effect: snow belts. Water bodies create creating moist air masses. In winter, warm lake air rises, blocked by cold air on top, resulting in snowfall and the creating of snow belts around the lakes. Global Climate change Note: CO2 levels did NOT increase since industrial revolution. Northern atmosphere has more variability in atmospheric concentration because of the land-water proportion. Other greenhouse gases: methane, CFCs, tropospheric ozone, SOx, NOx Temperature anomalies: Northern hemisphere has the most extreme changes in temperature. Extreme latitudes have MORE increasing temperature. What causes cooling Human induced cooling: increased tropospheric aerosols (increased scattering) cloud changes land-cover alteration—increased albedo Natural causes volcanic aerosols have both warming and cooling effects Greenhouses gases has outweighed these cooling effects. Indications of climate change 1) Sea Ice: Scanning Multichannel Microwave Radiometer (SMMR) capture sea ice extent. Sept 16 2012 sees record low in theArctic sea ice. 2) Active Layer Detachments: active layer is getting deeper. Detachment happens like carpets rolling down, exposing permafrost underneath (positive feedback). They expose soil organic matter for microbial activity, which releases more CO2. 3) Retrogressive thaw slumps: Develop due to thawing of ice-rich permafrost on slopes. Thawing turns exposed ice-rich permafrost into a mud slurry which falls to the base of the exposure and flows downslope 4) Arctic shoreline: retreat of sea ice, more storms and more erosions 5) Sea level: has risen ~1.7 mm/yr due to increased thermal expansion and melting LAND ice. 14 / 32 6) Snow cover: decreasing, lowering albedo, decline of glaciers. Shorter winter, increasing growing season. 7) Snow Depth: percent snow depth change in March are decreasing. 8) Coral Bleaching: colourful algae are expunged because they cannot be supported by coral at warm temperature; coral becomes pale and eventually die. 9) Mountain Pine Beetle: because of warming, beetles are invading North. Refer to Pages 86-95; Appendix 4.1 for more Special lecture: permafrost Permafrost=any ground material frozen for two or more years. Thicker in the north. Can be alpine or below arctic coasts below ocean (formed in the past when sea levels were lower). Active layer gets thinner in north. Soil heats the most at surface, cools until the base of active layer. Types of permafrost is classified by ground ice differences. 1) Fine grained soil (clay and silt) are frost susceptible and readily form ice 3) massive bodies of ice. As water freezes, it expands by 10% and overlying soil heaves. Permafrost warms with depth due to geothermal heat from radioactivity. However rate of temperature change diminishes as you go down because not subject to surface temp change. In spring, energy conducts from active layer down; In autumn, atmosphere cools and heat gain becomes heat loss. Cryoturbation: cycle of freeze-thaw gradually moves soil material, results in landforms like hummocks, sorted circles, etc. Ice-core mounds/hills: large amounts of water creates heaving. Eventually soil will rupture and collapse, and then ice becomes exposed and melt. These are therefore cyclical and not permanent features. Frost wedges: soil cracks in winter, become partially filled up and thaw in summer. Repetition creates frost wedges. Thermokarst: when ground ice thaws and water drains, this causes subsidence and may form thermokarst lakes/land failures. other types of disturbance: on slopes, active layer detachments moves usually as a large area of intact soil and vegetation. This presents high risk to infrastructure and pipelines. Retrogressive thaw slumps: Circular scars that expose ground ice. *Increased disturbances causing enhanced erosion into rivers. This affects ecosystem. Land uses can cause thermokarst Adaption: You can’t put pipes underground because they will freeze, so they put heavily insulated above-ground pipes. They do not cause permafrost to thaw. Also, buildings are built on piers so they don’t heat up ground ice. Permafrost disturbance susceptibility modeling: Location of ground ice and areas susceptible to disturbances: You can measure amount of radiation, wetness, slop position, and combine them together to map out the areas. Then if you want to build a pipeline you can refer to the map. 15 / 32 Chapter 11 Solid upper mantle is ultramatic under the crust. Crust: 8-80 km thick, thinnest under oceans and thickest around Himalayas (due to converging crust underneath). Composition mostly oxygen, then silicon. Inner core=largely iron; outer mantle and crust silica-based. Rocks are made of minerals, which have definite chemical compositions. Most minerals have a crystalline structure. Igneous rocks: solidified from magma. - Intrusive (below surface) more common: granite, coarse - extrusive: through volcanoes, etc rhyolite, fine and glassy. - Felsic: silicate, light, formed at low temperatures. e.g. Granite (felsic intrusive;) - Mafic: iron and magnesium rich, dark, formed at high temperatures. e.g. Gabbros (mafic intrusive) In NA, igneous rocks found in east, west and arctic coasts, which are remnants of ancient oceans. Sedimentary rocks: thin layer on top of sedimentary and metamorphic rocks; In Eastern Canada, Sedimentary rocks worn away, exposing abundant igneous and metamorphic rocks. - Clastic: from eroded rocks. sandstone (sand), siltstone (from silt), shale (from clay); - Chemically precipitated: limestone - Organic sediments: plants and animals, like coal. Hydrocarbon compounds, interbedded with shale, sandstone and limestone strata.  Oil deposits and natural gas are classified as mineral fuels rather than minerals. They usually occupy porous sandstones. Metamorphic rocks: physically or chemically altered igneous/sedimentary rocks in their SOLID state; usually formed during crustal movement. Igneous Sedimentary Metamorphic Granite (felsic) Sandstone (sand) Marble Gabbros (mafic) Siltstone (silt) Slate (shale) Batholiths Shale (clay) Schist (shale) Basalt (extrusive) limestone Quartzite Rhyolite (extrusive) coal Gneiss (old rock close to magma) Rock cycle: interaction between surface (external) energy and subsurface (internal) energy 16 / 32 Chapter 12 Oceanic crust is entirely mafic Continental crust: upper part felsic, lower part mafic. Lithosphere: upper mantle and crust (150 km). 19 plates slide over soft and plastic asthenosphere (below lithosphere) Eons: the major divisions in geologic time scale; Precambrian: older than 542 million years (Ma). Includes 3 older eons. Pharnerozoic Eon: 542 Ma to present. Eras: subdivisions of eons. Then subdivided into periods and epochs. So: Eonserasperiodsepochs  age Plate tectonics: means motion of plates and interactions at boundaries. powered by Earth’s internal heat, esp. convection. Divergent: 1) ridges: or axial rift. Young rocks with matching age on each side 2) split continents/new oceans Continental margins: where ocean lithosphere meets continental lithosphere (doesn’t mean different plates though) Convergent: 1) continental-continental (Himalayas) 2) Continental-Oceanic (coastal mountains, oceanic trench, volcanoes) 3) oceanic-oceanic (volcanic Island arcs) Transform: e.g. San Andreas. Relief Features of the Continent Continental shelves: where land is connected to ocean. Beyond shelves, ocean depth drops rapidly. If we count the shelves as part of the continents and not oceans, the continent-ocean ratio would be 35:65 instead of 29:71. Active mountain building (volcanism and tectonic uplift) e.g. Alpine chains; Inactive stable crust: includes 1) continental shields (ancient igneous and metamorphic rock like Canadian shield) and 2) mountain roots (old, worn-down mountain belts adjacent to shields) Continental drift: most recent cycle is the Pangea’s breakup. We figure this out by: 1) fossil records 2) same age/characteristic of rocks 3) consistent glacial formation 17 / 32 Chapter 13 Two major geomorphic processes: Initial/Primary: produced from tectonic activities (internal) Sequential/Secondary: shaped by denudation, frost, rain, etc (external) Volcanoes: initial landform built from lava and ash. Active: erupted in recorded history; Dormant: not seen to erupt, but has erupted before; Extinct: never erupted; evidence of long-term weathering and erosion. Stratovolcanoes: mostly formed over subduction margins, layers of ash and tephra. Felsic, viscous, explosive. Calderas: large, steep-sided hole in the ground after eruption/collapse of stratovolcano. Can form caldera lake. Shield volcanoes: basaltic magma, fluid, spread over large areas with subdued eruptions. broad, rounded domes. Hotspots: volcanoes not formed at subduction zones but stationary spots in the earth. e.g. Hawaii/Jemez Mountains, New Mexico. Hot springs/geysers: ground water heated by hot rock and molten material near surface. e.g. Iceland, Japan. Compression: converging boundaries, results in mountain chains and rock folding Extension: happens at separating plate boundaries. Orogenic processes: from orogeny—origin of the mountain. Fold belts: result of compression, spread over 100s of km, a serious of anticlines (ridges) and synclines (trough/downward folds). Can be eroded to from complex secondary landforms; Fault landforms: 1) normal faults 2) reverse faults result in: Overthrust: one piece of land pushed over another (see diagram of overthrust fold) Horst feature (pushed up) due to compression; Graden feature:(dropped down) due to extension 18 / 32 Chapter 14 Denudation: Landscape features develop according to bedrock composition and structure. Decreasing rock denudation rates: Sedimentary  metamorphic  igneous  Weathering has to do with only the disintegration of rocks;  Erosion has to do with the denudation and movement of earth materials Weathering: rock worn down to regolith. physical/mechanical: No chemical alteration. The type of debris determined by 1) rock type and 2) structure of cracks/joints. Surface area is increased during weathering,
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