Geology and water Flashcards
Define what an ocean is
large areas of the ocean floor artificially divided by continental boundaries
i.e pacific, atlantic, indian, arctic, antarctic
Define what a sea is
smaller areas of ocean floor partially enclosed by land
What is the name of the movement of landmasses due to plate tectonics?
continental drift
What did the oceans look like during the Permian period?
large Panthallasic ocean, smaller Tethys ocean, smaller Paleo-Tethys ocean
What did the oceans look like during the Jurassic period?
Pacific ocean, Tethys ocean, small early formation of the Atlantic ocean, formation of the Gulf of Mexico
What did the oceans look like during the Cretaceous period?
Pacific ocean, North Atlantic ocean, South Atlantic ocean, Arctic ocean, Tethys ocean
What is a rift zone?
point where two tectonic plates diverge
What is a subduction zone?
point where two plate tectonics converge
How do the Galapagos islands prove the age hypothesis of rift zones?
islands farther from the rift zone were shown to be older than islands close to the rift zone
What is the continental margin?
transitional area between the edge of the continents and the open ocean
What is the continental shelf?
- shallow (<100m) and flat extension of the continents
- influenced by sediments
- wider in areas of flat terrain, narrower in mountainous coasts
- formed through wave erosion, sediment trapping and deposition
What is the continental slope?
- steep slope (100 - 3200m)
- little sediment
- underwater canyons
What is the continental rise?
- shallower slope (3000-5000m)
- deep sediment deposits
- prominent in Indian and Atlantic oceans
What is the abyssal plain?
- dark, unproductive area covering 1/2 of global surface
- 3000-6000m deep
- flat and covered in sediment
What are seamounts?
extinct underwater volcanoes that contain a high diversity of marine life
What are trenches?
deep narrow troughs (7-11000 m deep) around volcanic regions
What two components make up mud?
clay (<0.004mm) and silt (0.004-0.062mm)
How big is sand?
0.0062-2mm
What four components make up gravel?
granule (2-4mm), pebble (4-64mm), cobble (64-256mm) and boulder (>256mm)
In what ways is sediment formed?
hydrogenous = precipitate from seawater
biogenous = dead organic matter (ooze)
terrigenous = eroded continental rock
cosmogenous = iron deposits from outer space
What are the compositions of water on earth?
oceans = 97%
ice = 2%
surface water = 0.02%
groundwater = 0.5%
What is a polar molecule?
charged molecules that are asymmetric, so the charges do not cancel out
How does polarity affect water molecules?
- allows them to form hydrogen bonds
- attracts water molecules to each other
- gives it a high boiling point (100c) and freezing point (0c)
- hydrogen atoms in ice repel each other, giving ice a lower density than liquid water
- makes water a universal solvent (can bind to both negative and positive molecules)
What are the properties of water
- cohesion = tendency for water molecules to stick to each other and to polar molecules
- surface tension = surface molecules have a higher affinity for each other than with air molecules and creates a tight surface barrier
- high viscosity = colder water makes it harder for objects to break space between molecules and move through
- capillary action = movement of water through narrow spaces as a result of cohesion, allows for water to penetrate sediment
- high heat capacity (ability to change 1g of water by 1c), requires more energy (4.6 J) to increase temperature vs other liquids, allows oceans to maintain a relatively constant temperature and for animals to disperse heat internally
How does light penetrate the oceans?
- only a small proportion of light reaches lower depths
- no light pass 1000m
What 6 ions are found in ocean water to make it salty?
sodium (Na, 10.8g/kg)
chlorine (Cl, 19.4g)
sulphate (SO4, 2.7g)
magnesium (Mg. 1.3g)
potassium (K, 0.4g)
calcium (Ca, 0.4g)
Describe the salinity patterns globally
polar regions = low salinity due to annual ice melt
subtropics = high salinity due to low precipitation and high evaporation
Where do the salt ions come from?
- precipitation
- volcanic emissions
- river deposition
- seafloor rock erosion
How does salt get removed from the ocean?
- adsorption (salt binding to clay and locked in sediment)
- death of organisms
- removal of organisms (i.e fishing)
- sea spray onto shore
What are the oxygen patterns in the Pacific and Atlantic oceans?
- topmost depth = photic zone, high productivity means high oxygen levels
- oxygen minimum zone = below photic zone, oxygen depleted due to above activity
- below oxygen min zone = oxygen increases as oxygen rich water sinks from surface
What are the CO2 patterns in the Pacific and Atlantic oceans?
starts off lower at lower depths and increases as depths get bigger
What factors affect gas solubility?
- decreases as temp and pressure increase
- increases as pressure increases
What did Alfred Wegener hypothesize?
- Earth once had a super continent called Pangaea
- continental drift: continents broke apart and drifted due to plate tectonic movement
- used fossil and rock record distributions as evidence
- warm rock rises in magma and pushes cool magna further into mantle, creating currents
What is the magnetic polarity concept and how does it relate to continental drift?
- magnetite crystals point to north pole
- rocks of different ages will point to different north pole directions
- rocks of same ages pointing in different directions could be explained by continental drift
What did the paper by Durden et al. (2015) find?
- abyssal hills had coarser sediment than plains
- megafauna in abyssal hills had a higher biomass and diversity than in plains
- variation in terrain structure (hills) affected megafauna composition
