Oceanography Final – Flashcards
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Beach
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deposit of the shore area, consists of wave-worked sediments
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Backshore
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above high tide shoreline and covered with water only during storm waves
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Foreshore
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the portion exposed at low tide and submerged at high tide
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Shoreline
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migrates back and forth with tide and is the water's edge
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Nearshore
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extends seaward from the low tide shoreline to low tide breaker line
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Offshore
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deep enough that waves rarely affect the bottom and is beyond the low tide breakers
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Wave-Cut Bench
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A flat, wave-eroded surface
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Shore
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A zone that lies between the lowest tide level and the highest elevation on land that is affected by storm waves
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Coastline
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Marks the boundary between the shore and coast
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Berm
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the dry, gently sloping region at the foot of the coastal cliffs or dunes
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Beach Face
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the wet, sloping surface that extends from berm to shoreline
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Low-tide terrace-longshore bars
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sand bars parallel to the coast that are exposed during extreme low tides
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Longshore trough
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region separating longshore bar and beach face
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Beach Sediment Sources
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streams, cliffs and bluffs, offshore shelf, dunes, longshore transport, artificial nourishment
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Littoral Drift
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directions and rates are important to coastal processes and key to understanding the effects of coastal engineering structures on shoreline. Alongshore and on- offshore transport of sand takes place as a function of wave energy and angle of wave approach, and of seasonal changes in wave energy (winter to summer differences)
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Sinks for littoral sand
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submarine canyons, dunes, mining, offshore mining
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Erosion
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The removal of soil and rock from the earth's surface by exogenic processes, such as wind or water flow
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Accretion
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A slow addition to land by deposition of water-borne sediment; an increase of land along the shores of a body of water
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Coastlines are either...
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eroding, accreting, in equilibrium
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Factors influencing variations in coastline morphology
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a. Tectonic history or activity b. Sediment supply and presence/absence of a protective beach c. Recent sea level changes d. Resistance of materials to erosion e. Wave energy and direction f. Climate and weathering/storm frequency g. Organic activity h. Human activity/coastal engineering structures
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Leading Edge Coast
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A coastal area that is the site of convergent or transform plate motion; associated with uplift, and a steep coastline cut by high energy waves (Pacific Coast of USA)
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Collision Coasts
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A coastal area that lies along the edge of a convergent plate; often associated with earthquakes and volcanic activity (Pacific Coast of USA)
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Trailing Edge or Passive Margins
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Atlantic Coast of USA
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Marginal Seacoasts
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Gulf of Mexico
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Tectonic History of Coasts produces variations in...
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a. landforms on and offshore b. Earthquakes and volcanic activity c. Submarine canyons d. Rivers: size of basins, sediment load/yield
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Pacific Decadal Oscillations (PDO)
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Changes ocean conditions around Pacific on 20 to 30 year cycle
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El Nino and La Nina events have short-term effects on...
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• Sea level • Wave height • Water temperatures • Which change: - Weather - Rainfall - Storm approach - Distribution of marine organisms
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El Nino (physical and terrestrial effects)
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- Storm waves - High rainfall - Floods - Erosion - Landslides - In Americas: -Droughts -Forest fires
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El Nino (cultural effects)
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- Changes in agriculture - Changes in fisheries
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Climate change from natural causes
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- Short term solar cycles - Volcanic eruptions - Plate tectonics - Earth's orbital variations
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Milankovitch cycles
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theory states that the Earth's orbit affects its climate; changes in tilt change length and strength of seasons
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Eccentricity
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fluctuations between oval orbit and circular orbit, is complete/happens every 100,000 years, causes colder periods in temperature
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Obliquity
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The earth is on a tilted axis which means certain parts of the earth get more sun than others at certain times
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Wobble
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shortest period, 23,000 years, the Earth wobbles like a spinning top, wobbling back and forth
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Climate change from anthropogenic
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- Greenhouse gas production - Annual CO2 production - Contribution of CO2
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Greenhouse Gas Production
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- 14% from transportation - 16.8% from industry - 21.3% from power production - 3.4% from waste disposal - 10% from land use/biomass - 10.3% from residential/commercial activities - 11.3% from fossil fuel retrieval/drilling/transportation
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Annual CO2 production in tons
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- 3,245,000 tons/hour - 1*(10^6) tons/hour get absorbed into the ocean - 50 times more CO2 in the ocean than in the atmosphere
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Contribution of CO2
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- World - 28,431,700,000 tons - 100% - average of 4.4 tons per person - China - 6,103,000,000 tons - 21.5% - 4.6 tons per person - USA - 5,752,000,000 tons - 20.2% - 19 tons per person
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Records of climate change from
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- Ocean drilling- back ~ 200,000,000 years - Ice Cores: back 800,000 years - Tide Gages: back 150 years - Satellite Altimetry: back 20 years
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Sea level changes are absolute (global) or relative (local)
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- Most sea level changes are climatic in origin - Some tectonic: - Related to rates of seafloor spreading and volume of ocean ridges
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Climate changes related primarily to cyclical changes (Milankovitch cycles) in Earth's orbit and therefore distance from sun and solar energy
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- Wobble on axis ~ 21,000 year cycle - Tilt of Axis of Rotation ~ 46,000 year cycle - Eccentricity of Orbit ~ 100,000 year cycle
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Due to regional tectonic setting, relative sea level may be...
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- Rising rapidly in places like New Orleans due to Mississippi delta sinking - Falling in Alaska due to glacial rebound of land (isostasy) - Staying about the same in San Francisco
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El Niños, hurricanes, typhoons, tsunamis, and other short-term events have...
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very significant short-term effects on sea level
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Global Warming
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- Agreement on warming - Magnitude and rate of changes unresolved - Causes have been determined Primarily: • Greenhouse gases • Carbon dioxide • Methane • Chlorofluorocarbons
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Future rates of sea-level rise very dependent upon rates of greenhouse gas emissions...
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Sources include: - Fossil fuel burning - Transportation - Industrial - Agriculture etc.
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Hydraulic Impact
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is the propagation of fractures in a rock layer by a pressurized fluid. Some hydraulic fractures form naturally - certain veins or dikes are examples - and can create conduits along which gas and petroleum from source rocks may migrate to reservoir rocks. Induced hydraulic fracturing or hydro fracturing, commonly known as fracking, is a technique used to release petroleum, natural gas (including shale gas, tight gas, and coal seam gas), or other substances for extraction. This type of fracturing creates fractures from a wellbore drilled into reservoir rock formations
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Abrasion
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is the mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion. After friction, the moving particles dislodge loose and weak debris from the side of the rock. The intensity of abrasion depends on the hardness, concentration, velocity and mass of the moving particles
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Solution/Weathering
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Weathering is the breakdown of rocks, soils, and minerals that occurs 'in situ' (meaning without movement)
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Physical Weathering
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direct contact with atmospheric conditions (heat, water, ice, and pressure)
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Chemical Weathering
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direct effect of atmospheric chemicals or biologically produced chemicals
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Biological Activity
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snails, grinding/eating surface layer
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Variables in shoreline erosion:
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- Rock resistance - Structural weaknesses o Joints o Fractures o Faults - Wave exposure - Beach presence or absence - Storm frequency - Tidal range - Human impacts
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Erosion process is episodic or irregular...
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Rates are taken as averages from measurements taken from historic aerial photographs or maps
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Hazardous coastal environments for human habitation...
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- Eroding cliffs - The back beach - Sand dunes
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Solutions or alternatives to areas undergoing shoreline erosion...
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- Retreat or relocate structure - Sand nourishment (costs/responsibilities/lifespan) - Armoring or protection
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Battering
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wave impact or debris impact
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Overtopping
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wave going over
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Undermining
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collapse and settlement
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Outflanking
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waves going around
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Seawalls and revetments have well defined impacts:
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- Visual effects - Loss of beach area-placement loss - Loss of sand to beach formerly provided by eroding bluff or cliff - Reduction on beach access - Passive erosion
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Renewable resources
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fish and shellfish
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Non-Renewable resources
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o Mineral Resources - Heavy minerals/metals - Manganese nodules - Sand o Energy Resources - Oil - Gas
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Physical resources
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- Water - Beaches - Waves
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Fossils fuels and their formation
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oil and gas-marine
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Coal-Terrestrial
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Formed in bogs and swamps
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Oil pollution from...
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- Natural seepage - Drilling - Tankers and spills
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Renewable Ocean Energy
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- wind - wind farms - tides - wave
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Varying types and levels of pollutant impacts
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- acute - chronic - synergistic - biological magnification - cellular - organisms - community - population
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Biological Magnification
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Organisms and animals lower on the food chain absorb toxic materials while animals higher up on the food chain consume these organisms. As a result the animals higher up on the food chain accumulate all of these accumulated pollutants and toxic materials. Because they mass consume the organisms lower on the food chain, it becomes increasingly more concentrated each step up the food chain
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Cellular
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felt in minutes to hours
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Organisms
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hours to months
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Community
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years to decades
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Population
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months to years
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Domestic sewage and solid waste
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o Constituents: - Oxidizable organics - Nutrients - Chemical constituents - Virus and bacteria o Effects on the marine environment
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Primary (Levels of wastewater treatment)
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Removal of solid particles from the wastewater. Wastewater is filtered through fine screens to remove solid matter like paper, cotton, and plastic. Heavy particles like, sand, sink to the bottom and are removed. Wastewater then flows to sedimentation tanks where human waste (sludge) settles to the bottom and oils and grease float to the top and are removed
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Secondary (Levels of wastewater treatment)
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Removal of dissolved and suspended organic and inorganic solids through bacterial decomposition which breaks down the material
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Tertiary (Levels of wastewater treatment)
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Further removal of inorganic compounds and substances like plant nutrients nitrogen and phosphorous
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Industrial/Agricultural discharges
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- Heavy metals (lead and mercury) - Toxic chemicals - Chlorofluorocarbons - Chlorinated hydrocarbons - Other organics (DDT, PCBs, etc.)
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Electrical Power Generation
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- Thermal effluent and impacts - Nuclear power and its release of radiation, radioactive waste storage, and concerns
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Nuclear Power and its release of radiation
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o Radioactive waste storage - Waste lasts between 200-500 thousand years - There are no operating long-term waste storage sites in the U.S. o Concerns
