Erth 307 Flashcards
Sub-disciplines of oceanography
Geological - Earth’s surface/seafloor
Biological - phytoplankton, marine organisms, productivity, food webs
Chemical - seawater properties, water column properties, coriolis effect, water transportation
Physical - tides, coastal processes, waves, ocean circulation
Ocean geography
the average depth of the ocean is way deeper than the average height of land
Ocean depth is measured directly or indirectly
Directly - weight on a measured length of line
Indirectly - pressure, sound waves, satellites
Aspect ratio
the average depth of the ocean is way deeper than the average height of land
Ocean depth is measured directly or indirectly
Directly - weight on a measured length of line
Indirectly - pressure, sound waves, satellites
Latitude
east-west; measures north-south
Longitude
north-south; measures east-west
changes in distance between lines
Hypsography
science of determination and mapping of the relative elevation of land and sea
Chemical composition of Earth
Crust
Mantle
Core
Physical properties of Earth
Lithosphere
Asthenosphere
Mesosphere
Outer Core
Inner Core
Continental Drift
Alfred Wegener; advanced to idea of mobile continents
Evidence of continental drift
Fit of continents together
Mountain ranges across continents
Glaciers and climate changes
Fossils
Drawbacks of continental drift
theory failed to explain why continents move
Wegener thought gravity pulled the continents
Sea-floor spreading
new seafloor (oceanic crust) is formed at the oceanic ridges, pulling apart
Paleomagnetism
Earth has a magnetic field that switches polarity, this is imprinted on new oceanic crust as it is formed at ridges
Theory of plate tectonics
Earth is made of lithospheric plates, new ocean crust formed at spreading centers, destroyed in subduction zones
Slab pulling and slab suction are main driving forces
New evidence for plate tectonics
Age of the seafloor - new age dating methods allowed for determination of age of seafloor, supporting seafloor spreading theory
Earthquakes support theory of plate tectonics
Convergent boundaries
come together
3 types depending on crust
Convergent 1
Oceanic-continental
continental arc formed
Oceanic crust is ALWAYS subducted because it’s DENSER than continental crust
Convergent 2
Oceanic-oceanic
Island Arc formed
Convergent 3
Continental-continental
Mountains formed
Divergent boundaries
spread apart
example - Iceland, Red Sea, and Mid-Atlantic Ridge
Transform boundaries
move parallel to one another
Isostasy
Isostatic equilibrium
Movement of crust in the vertical to steady state positions
Results from lithosphere riding on top of asthenosphere
The key is the different densities of crust types
Mid-ocean ridge variability
MOR is moving slower than EPR
Bathymetry
the measurement of ocean depths and the charting of the shape, or topography, of water beneath a ship
Oldest method
direct and intuitive
Measured with a line
1 fathom = 6 feet
Measuring depth
Soundings
Echo sounders
Multibeam sonar
Satellites
Active margins
occur at convergent boundaries
Passive margins
do NOT occur at plate boundaries
Marine sediments are made up of
Dead organisms
Wind blown dust
Volcanoes
Deep ocean water
Atmosphere
Marine sediments are
particles of various sizes from a variety of sources on the sea floor or coastal zone
Neritic zone
coastal, continental shelf areas
Pelagic zone
open ocean
Marine sediments can be
of all different sizes and provide a very complete record of climate conditions
Lithogenous
Derived from land sources
Typically made of quartz
Can be sorted by grain size (range from fine grain to pebbles or boulders)
Biogenous
Derived from biology (dead organisms)
Calcium carbonate and silica
Microscopic
Hydrogenous
Precipitated out from dissolved substances in seawater (like hydrothermal vents)
Cosmogenous
Space-borne dust (like meteors)
CCD (Calcium Carbonate [Calcite] Compensation Depth)
the depth at which the rate of carbonate accumulation equals the rate of carbonate dissolution
Destruction
Settling velocity
Depends on the weight and size of sediment particle
Under the condition of equilibrium between the gravitational and drag forces on the settling particle
Turbidity currents
Conduits for lithogenous sediment to deep ocean (called density driven currents)
Why is water unusual?
High specific heat
Hydrogen bonds
High boiling and melting points
Solid phase expands, less dense than liquid phase
Universal solvent
Polarity
Essential to life
Specific heat capacity
Very high specific heat (amount of heat needed to raise 1 gram of a substance 1 degree C)
Hydrogen bonds
Weak bond; direct result of polarity
Forms between adjacent water molecules (leads to water being ‘sticky’)
Density
mass/volume
Related to molecule structure and why its density changes with temp
Fresh water’s temperature of max density is 4 degrees C
Function of Salinity, Temperature, and Pressure
Salinity
Total amount of solid material dissolved in water
Measuring salinity
Evaporate and weigh salt left over
Chlorinity; measure amount of Cl, can get total salinity of water (PRINCIPLE OF CONSTANT PROPORTIONS)
Conductivity; measure electrical conductivity of seawater, directly proportional to dissolved ions in sample
Processes affecting salinity
Runoff (rivers)
Precipitation
Evaporation
Sea ice melt
Sea ice formation
Icebergs melt
Conservative forces
Long residence times
Little or no change over time
occur in constant proportions in seawater (includes major consitituents [Cl, Na, Ca, K])
Non-conservative forces
Significant change over time
Short residence times
Variability over oceans; biologically active/reactive (includes O2, CO2, nutrients [nitrate])
Residence time =
volume (or mass of stuff)/flux of stuff
Surface T and S patterns
Vary in time and space
Vertical variations exist in both
Horizontal variations in T and S change in time, but major patterns exist
Latitudinal trends in T and S
High latitudes: lowest S; precipitation + runoff + ice melt; cooler temps = less evaporation
Mid-latitudes: high S; little precipitation and runoff; high evaporation rates; warmer air descends near tropics of Capricorn/Cancer
Equator: relatively low S; warm air = high evaporation rates; offset by high precipitation and runoff
Halocline
Rapid change in salinity with depth
Separates layers in ocean
Can go either way
Thermocline
Rapid change in temperature with depth
Separates layers in ocean
Can go either way or be absent altogether
Seasonal thermocline
Develops over seasonal cycle
Depth and strength of thermocline changes in time
Temperature has a large effect on density
Inversely related
Lighter water resides over top denser water
Pycnocline
Rapid change in density with depth
Separates layers in ocean
Pressure
Temperature ↑ = density ↓ (thermal expansion)
Salinity ↑ = density ↑ (more stuff in some volume of water)
Pressure ↑ = density ↑ (more stuff in some volume of water)
Dissolved gases
Amounts in seawater vs atmosphere depends on
Solubility
Percent of atmosphere
Amount of O2
Surface: high
Intermediate depths: decreases rapidly
Greater depths: increases
Amount of CO2
Surface: equilibrium with atmosphere
Intermediate depths: increases
Greater depths: decreases
Changing pH in oceans
Ocean buffering - carbonate is ocean’s buffer
As CO2 goes up, pH goes down (slowly becoming more acidic)
pH changes are not the same everywhere
