Oceans , week 2
Oceans , week 2 OCEA 1 - 01
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OCEA 1 - 01
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This 4 page Class Notes was uploaded by Elyse Villanueva on Friday October 7, 2016. The Class Notes belongs to OCEA 1 - 01 at University of California - Santa Cruz taught by Carl Lamborg in Fall 2016. Since its upload, it has received 2 views. For similar materials see The Oceans in Scientific Inquiry at University of California - Santa Cruz.
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Date Created: 10/07/16
October 3 Oceanic crust is recycled regularly, whereas continental rust includes very old rocks evidence for plate tectonics : coastal geometry, fossil records, earthquake patterns, heatflow patterns, magnetic stripes of ocean floor, age of oceanic crust, sediment thickness, and gps observed measurements. asthenosphere: lower portion of upper mantle(plastic, can flow) lithosphere: rigid, uppermost mantle plate: crust and uppermost mantle plates float on the mantle...destruction of seafloor divergent boundary: mantle upwelling, layers of oceanic crust convergent: plates collide and often subduct where plates diverge mid ocean ridges form spreading center is where new oceanic crust forms new oceanic crust is always being made oldest crust is 200 megayears old in oceanic vs oceanic(convergent boundary) old crust gets subducted and trenches form as well continental crust is lighter oceanic vs continental makes volcanic mountains continental vs continentalno winner and mountain belts form. No subduction but instead pushing up birth and death of ocean basins( wilson cycle) we map ocean by using sound(echo sounder or precision depth recorder) send out a pulse of sound and listen to echo with machine using travel time D=½ x V x T Speed of sound in sea water is 1.5 km per sec 5% of seafloor mapped various satellites: jason, TOPEX/poseidon, ERS, GFO we also use electromagnetic gravity of seafloor peaks water towards the peak which we can see by satellite active margins: plates interacting with eachother passive: no tectonics continental shelf: continental crust overlain by sediment turbidity current: huge undersea avalanche where that sets forms turbites October 5 The arctic ocean is the “shelfiest” ocean, this is why its average depth is shallowest of all oceans. seamounts and abyssal hills are the same thing they just differ in size hawaiian island chain, formed by hotspot in mantle. they thought that the mantle hotspot stays in the same spot but plates move (like moving a piece of paper over a candle) evidence from paleomagnetic record that mantle plume also moved (in candle example that means the light flickers) enormous implications for plate reconstruction flat topped seamounts are called guyots or tablemounts traditional view of formation: ocean depth increases away from spreading center( called subsidence) have action (subaerial weathering) flattens top guyots might be formed by coral reefs coral reefs secrete cement which is CaCo3 as skeleton as the island erodes away, the coral continues to grow up and creates a ring (atoll) reefs form foundation, with sediments falling on top main features of ridges: vent fields hydrothermal vents: cracks on rocks that are close to magma and water boils creating chemistry. chemosynthesis: not growing on light (photosynthesis) but instead growing on chemicals rich environment around vents very little data about trenches James Cameron dove to challenger deep H2O: 2 hydrogen and one oxygen atom covalent bonds polar molecule...b/c O is more electronegative than H Hydrogen bonds.. The H of one molecule bonds w/ the O of another atoms and molecules are always in motion temperature...measure of the average kinetic energy of atoms or molecules, measured in F, C, K Heat.. Measure of total amount of kinetic energy.. Therefore more mass holds more heat measured in calories(or joules if using SI) change of state: hydrogen bonds, latent heat of fusion, latent heat of vaporization sensible heat… associated with temp changes latent heat: extra energy required to go from a more condensed phase to a less condensed phase is given back when going from less condensed to more. specific heat of a material ocean is slow to heat up, slow to cool down.. Tends to moderate coastal climate density increases w/ decreasing temp to 3.98 C, decreases w/ decreasing temp from 3.98C to 0C. Density decreases at the phase transition from liquid to solid… ice floats salt water has greatest density to 0C, not 4C as with fresh water density increases w/ salinity compressibility.. Air and water are very different water is almost incompressible, at different pressures, the density of seawater does not change much air is highly compressible Wien’s law… the “color” of radiation is a function of temperature Wien’s law in action...when rocks are very hot they glow red water absorbs light l(z)=l ek * z 0 z=depth k=attenuation coefficient light decays exponentially from the surface October 7 Salinity is the total amount of solid material dissolved in water. 86% of ocean salt is sodium and chloride there are 89 other chemical elements found in small proportions basic elements(95%): cl, Na+, SO4^2, CA^2+, K+, and trace elements for every thousand gram per seawater 35 is going to be sodium (3.5%) ocean salinities: spatial variations, processes that affect salinity. (controls salinity in ocean:evaporation, precipitation, runoff, freezing, and thawing) surprisingly uniform(oceans are well mixed) Atlantic ocean has highest salinity rivers discharge carries sediments into ocean sources of salinity: riverine, volcanoes, and hydrothermal vents. in glaciers, when it freezes the salt doesn’t freeze in the glaciers. sinks: adsorption and precipitation, sea spray, hydrothermal activity, and biology biology: organisms use it to form shells ultimate source is rock, either at surface, or from the deeper in the crust or upper mantle. fluxes are in units per time (grams/ year) residence time: the average length of time in which a substance or portion is in a given location or condition, such as adsorption or suspension. adsorption: the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. ocean is steady or at a dynamic equilibrium chemistry of ocean salts isn't changing much but always in motion. input fluxes=output fluxes or sources=sinks organisms create material that is buried in sediments=primary way that dissolved constituents are removed from ocean iron is an essential part of photosynthesis relative concentrations of ocean will be constant( constancy of proportions) any other non major element/ion that has a long residence time in ocean will have a relatively constant ratio relative to salinity( a conservative element) conservative element: sticks around for a while and it is not useful to light photosynthesis is a key chemical process converts light energy into chemical energy oxygen is the product, autotrophs do this. phytoplankton is the main group of autotrophs photosynthesis removes CO2 and produces O2 at the surface. respiration produces CO2 and removes O2 at all depths biological pump puts carbon into the ocean food web processes transfer organic matter to depth. all the carbon moving down is part of the food chain, it is eaten by bacteria. nutrients are essential for biological growth macronutrients: phosphorus, nitrogen, and silicon micronutrients: iron they are needed by phytoplankton in ratios phytomass displays an average composition of C106: N16: P1 major nutrients are used up by life in surface.. Released from biological pump deeper down. Leibig’s law of the minimum: the amount of crops you can get from a field is limited by nutrient you have the least of. John Martin: add iron to plankton from certain areas.. You get more growth adding iron to ocean will stimulate phytoplankton growth which will drag down CO2 in the atmosphere, on way to remove pollution O2 from air into ocean. this is being considered as a part of mitigating climate change
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