Oceanography (EPSS 15) Lab Final

island arcs

another kind of pacific type margin; typically in the western Pacific

abyssal plains

found near some Atlantic type margins when sediments from turbidity currents have flowed off continental rise and spread out over sea floor to produce extremely flat stretches of sea floor; cover approximately 40% of the ocean floor

continental rise

gently sloping depositional surface at the base of the continental slope

continental shelf

gently sloping depositional surface extending form the shoreline to the continental slope

equator

great circle around the Earth that includes all points equally distant from the poles

euphotic zone

region from surface to critical layer where photosynthesis dominates

continental slope

relatively steep surface seaward of the continental shelf

pelagic zone

the open ocean

plankton

"drifter"; small organisms that float and most live in or right under the photic zone; most are algae that form the base of the food chain; contribute to biogenous sediments in the form of deep sea oozes; two types: phytoplankton and zooplankton

acidity and alkalinity

H+ adds acidity, OH- makes it more basic; pH is negative log of H+ concentration; pH goes from most acidic (0) to most basic (14), with water being neutral at a pH of 7

pycnocline

a region where large gradients in temperature and or salinity separate less dense surface waters form more dense deep water; gradients form a layer of water with rapidly changing density

isostasy

a rigid body will displace its weight in a liquid; think Archimedes in the bath tub; if they are the same shape and volume, less dense objects will float higher in the liquid than objects which are denser; if they are the same density, large blocks float higher than smaller blocks because they displace more water (and the buoyancy force is therefore greater); the earth consists of blocks of rigid lithosphere that are floating in isostatic equilibrium on a plastic asthenosphere

hot spots

a type of volcanic activity in the intraplate region; produce stationary volcanism for millions of years; responsible for island chains, and can be found in all ocean basins; chains of extinct volcanic island terminate at the youngest volcanic island; moving rate can be calculated given distance between volcanic islands and time period

thermohaline circulation

another name for deep ocean circulation; below pycnocline, deep waters move in sluggish currents that are driven by gravity; differences in density cause dense masses to sink under the force of gravity; takes roughly 1000 years for deep water to circulate

prime meridian

arbitrarily chosen to be at Greenwich, this is the line at which longitude is 0 degrees

Submarine fans

associated with the mouths of submarine canyons; e.g. Indus and Ganges Cones

ice rafted sediment

at high latitudes, glacial marine sediments that are deposited at the fronts of glaciers or in the deep ocean when icebergs drop sediment as they melt

carbonate buffer system

bicarbonate ions buffer sea water to keep it in the neutral/slightly alkaline range; 7.5-8.4 range

calcareous oozes

calcium carbonate; marine organisms' skeletons are constructed from calcium carbonate mineral calcite; aragonite, its other form, is in the shells of pteropods, but dissolves easily in water, so is only really preserved in relatively shallow, warm, tropical waters; biogenous sediment; deep cold waters high in CO2 concentration corrosive; depth below which calcite is dissolved is the Calcite Compensation Depth; oozes found in shallower regions of ocean floor, like ocean ridges, plateaus, basins, and sea mounts; coccolithophores and foraminifera

phosphates

calcium phosphate; common skeletal mineral in bones and teeth of vertebrates; stable mineral that doesn't degrade easy; usually a minor component of deep sea sediments; biogenous sediment

Mid Ocean Ridge and Rise system

chain of mountains in 60,000 km long; central rift valley as deep as 1 km; rugged flanks; stand 1 to 3 km above deeper ocean basin and is often offset by fracture zones; where new lithospheric material is created as oceanic plates diverge; characterized by high heat flow, volcanic activity, and shallow earthquakes

magma arcs

chains of volcanoes that lie parallel to the trenches and above subducted slabs of lithosphere; partial melting of the mantle over the subjecting lithosphere produces magmas that rise to the surface through fractures in the overriding plate

Antarctic Bottom Water (AABW)

cold saline water that forms as water freezes around Antarctica; flows down the shelf and slope of Antarctic, missing with other water and then flowing eastward with the Antarctic Circumpolar Current; also flows northward into Atlantic, Indian, and Pacific oceans; composes about 59% of world's oceans; generally, includes all Indian and Pacific ocean waters with temperatures less than 3C and all water in Atlantic less than 2C

aphotic

completely dark, no photosynthesis

oceanic crust

composed mainly of basalt, which is roughly 3.0 g/cm^3; roughly 5 km thick on average

continental crust

composed many of granite, which is roughly 2.7 g/cm^3; roughly 35 km thick on average

oozes

consist of tests, or skeletons, of single celled, microscopic organisms comprising of plankton; deep sea deposits are called oozes when they are composed of more than 30% biogenous material

contours

contours are lines drawn on a figure that connect data of equal value; lines never cross each other; v's that point uphill are troughs; v's that point downhill are ridges

density

controls deep sea circulation; dense sea water will sink to great depths; primarily a function of temperature and salinity; high density favored by low temperate and high salinity; coldest waters are usually the most dense

lithosphere

cool, rigid outer layer; about 100 km thick; crust and upper mantle

chemical properties of water

dipolar structure; highly polar and can thus form hydrogen bonds; high melting and boiling points; high heat capacity

descriptive classifications of marine sediments

distinguish based on differences in texture and composition; useful textural properties are size, shape, and roundness; compositional properties are mineral content, chemical composition, or biological constituents

genetic classifications of marine sediments

distinguish based on process by which they originate; biological, chemical, or physical

subtropical gyres

dominant components of surface circulation; large, crudely circular patterns of flow; clockwise in northern hemisphere, counter clockwise in southern hemisphere; extend from equator to north 45 and south 45; driven by trade winds as low latitudes and westerlies at higher latitudes; four components: equatorial currents driven by trade winds, western boundary currents (HOT) deflected by coriolis effect and continents, west wind drift driven by westerlies, eastern boundary current (COLD) deflected by coriolis and continents

volcanic islands and seamount chains

e.g. Hawaiian-Emperor Seamount chain

biological pump

exports products from photosynthesis to the deep ocean; regulation of CO2 content of atmosphere and O2 and nutrient content of deep sea

abyssal clays

fine-grained, silt and clay sized particles that are transported by wind to the deep ocean basins, far from the continents; type of terrigenous sediment; default sediment of deep ocean basins; found in regions where other sediment types do not occur and cannot dilute them, far form continually margins and bellow CCD and away from areas of high biological surface productivity

Equatorial currents

flow west along the equator where water tends to pile up against the continental margins

deep water

forms at the surface of oceans and then sinks to great depths and circulates throughout ocean basins; important sources include polar-subpolar North Atlantic and the Antarctic; NADW source in North Atlantic and flow down to mix with AABW then around Antarctica to Indian and Pacific; originally rich in oxygen, but as organisms respirate becomes more and more acidic and accumulate nutrients from organisms in surface waters that produce materials that dissolve in deep waters

Carbon Dioxide

highly soluble in sea water; produces weak carbonic acid, which disassociates to form hydrogen and bicarbonate ions; 90% of CO2 in ocean stored in bicarbonate ions; used in photosynthesis and to manufacture complex organic molecules in plant cells

seamounts

hills that are more than 1 km above ocean floor

core

inner and outer core; inner is solid, outer is liquid; generates electric field

cosmogenous sediments

inorganic sediments that originate by the accumulation of materials from outer space; cosmic spherules and impact deposits; very rare except near ancient meteorite impacts

hydrogenous sediments

inorganic sediments that originate by the precipitation of minerals from seawater; only a small portion of sediments; hydrothermal sediments produced by leaching at Mid Ocean Ridges, manganese nodules found in abyssal sea floor, and the continental analog is evaporates from dried lakes; exist in diverse environments such as Mid Ocean Ridges and ocean basins

zooplankton

microscopic animals that contribute to deep sea oozes; occupy primary and secondary consumer trophic levels of marine web; marine grazers that are very small; main food sources of both nekton and benthic organisms; main groups are copepods, krill, dinoflagellates, radiolarians, and foraminiferans; heterotrophs

manganese nodules

most common type of hydrogenous sediment; black, lightweight, show concentric layering; found on deep sea floor in regions of slow sedimentation

abyssal hills

most of the deeper ocean basins where water depth are around 5 km typically see these gently rolling hills; covered by much sediment, more than the mid ocean ridge system; most of the Pacific has abyssal hill morphology; topography more gentle than ocean ridge flanks

Active margins

narrow shelf and slope descending abruptly into a deep marginal trough, or trench, generally parallel to the continental margin; typical in the Pacific, such as off the coast of Chile and Peru; deepest trench in the Marianas Trench, but trenches in general are deepest places on the sea floor, and generally twice and deep as the ocean basins; high degree of tectonic activity

intermediate water

near high latitude ends of subtropical gyres where surface water not dense enough to sink to deep, waters mix; flow along isopycnals and are important in forming pycnocline; another source in relatively warm, saline water that flows out of Mediterranean and causes Atlantic to be saltiest of all major ocean basins

continent-continent convergence

neither can subduct so instead continent collisions; in some cases, pieces of ocean floor caught between continents; e.g. Zagros in Iran, Himalayas in Nepal, Alps, Urals, and Appalachians; mountain building creates highly deformed crust

subpolar circulation

north atlantic and north pacific, small sub polar gyres circulate in directions opposite to clockwise subtropical gyres; in southern hemisphere, where there are no continents to block surface currents, westerlies drive Antarctic Circumpolar Current

submarine plateaus, ridges and rises

not part of Ridge and Rise system

coriolis effect

objects in motions are deflected; surface currents move in different directions than the wind

transform boundary

occurs when two plates are moving parallel to each other but in opposing directions; plates slide past one another; some found on continents, like San Andreas fault, where two blocks of continental crust are sliding past one another; characterized by shallow seismic activity; more common transform faults are undersea, as seen in fracture zones that occur along mid ocean ridge systems; heat flow is low at transform margins; right lateral ("top" plate moves to the right) or left lateral ("top" plate moves to the left)

eastern boundary currents

on eastern margins of oceans, cold currents return colder water to equatorial region

plate tectonic theory

outermost division of earth consists of cool, rigid lithospheric plates which are in constant motion as they are driven by the internal heat of the Earth across the asthenosphere

deep ocean trenches

part of Pacific type, active margins; regions of plate convergence and subduction; characterized as seismically active with shallow, intermediate, and deep focus earthquakes

grain size

particle size is useful in classification and in determining the methods of transportation and accumulation of sediments within the oceans' boulder, cobble, pebble, granule, sand, silt, clay, colloidal; grain size indicates energy of area where it was transported from; smaller grains sink very slowly and remain suspended by slight turbulence in flowing water, so accumulate only where water isn't flowing rapidly, and they can also be transported by wind; larger grains sink rapidly, and can only be pushed along the bottom by fast-flowing water, and they accumulate in high energy environments

North Atlantic Deep Water (NADW)

particularly in Norwegian and Greenland seas; low temp and high rates of evaporation lead to production of cold saline water mass; sinks to bottom and flows south, eventually flowing over and mixing with AABW

dysphotic layer

photosynthesis no longer dominant; respiration outdoes photosynthesis

phytoplankton

photosynthetic plankton; original source of food for nearly all higher macroscopic marine organisms; autotrophic

salinity

physical property of sea water; salts derived from chemical weathering of crust and from volatiles from volcanoes; expressed in grams per kilogram; typically falls between 34 ppt (grams per kilogram) and 37 ppt; increases with evaporation and ice formation, decreases with precipitation, melting, river runoff, and groundwater runoff; higher salinity increases density, increases boiling point, and lowers freezing point

temperature

physical property of water; amount of heat store in the oceans; because of high heat capacity, ocean can store a lot of heat; temperature affects density: hotter water is less dense than cooler water; also affects solubility of water, as cold water dissolves gases from the atmosphere better than warm water

diatoms

phytoplankton which secrete tests of opal; diatomite is the name of the sedimentary rock composed mostly of the tests of diatoms; siliceous ooze and biogenous sediment; some live solitary and others in chains; regulate buoyancy to control suspension; rely on turbulent mixing of surface water through wind to keep them suspended in euphotic zone; mostly contain green chlorophyll, and may color the water green; some coastal diatoms release domoic acid, a toxin that moves up in food chains to cause illness, erratic behavior, and death

asthenosphere

plastic region of earth's mantle, upon which lithosphere floats; upper mantle; roughly 600 km thick

mesosphere

plastic, but stronger than asthenosphere; middle and lower mantle

divergent boundary

plate boundary where two plates are moving away from each other; magmas derived from the asthenosphere rise upward to fill the gap between the diverging lithospheric plates; ocean ridge and rise systems; young ocean basins, like gulf of California; and on land rifting, with high heat flow and volcanic activity; new basaltic crust is being created in sea floor spreading

convergent boundary

plate boundary where two plates are moving towards one another, usually with one plate being subjected beneath the other; can be head on or oblique; ocean-ocean convergence; ocean-continent convergence; continent-continent convergence; earthquakes can be shallow, intermediate, or deep as the plate continues subjecting and releases energy; heat flow is low in trenches, but high at the volcanic arcs

sources

processes that adds salts, like river waters, gases from volcanoes, fluids from hydrothermal vents

sinks

processes that remove salts, like incorporation into deep sea sediments or removal at ocean ridges

coccolithophores

produce skeletons of calcium carbonate consisting of multiple plates or coccoliths; compact to form chalk; calcareous ooze and biogenous sediment; too small for common light microscopes coccoliths can be shed during a coccolithophore's lifetime

hydrothermal sediment

produced at mid ocean ridges; hydrothermal fluids flow into the ocean through fissures and deposit metal rich deposits

principle of constant proportions

proportions of ions in the solution do not vary significantly from place to place if the solution is well mixed, as the open oceans are, though salinity may vary from place to place based in certain processes that add or remove water from the ocean

terrigenous sediments

sediments derived from weathering of the continents or from volcanic activity; erosion by rain, rivers, and glaciers delivers sediments from the continents to the oceans where they are deposited; most abundant in volume and mass; generally, terrigenous sediments on the deep sea floor far from continental margins are fine grained and transported by wind, called abyssal clays; very slow deposit rate; dominant along continental margins and in the deeper portions of ocean basins; essentially overwhelm biogenous sediments; glacial marine sediments dominate at high latitudes; turbidites dominate on continental rises and abyssal plains; glacial sediments dominate at high latitudes; range from course to fine

biogenous sediments

sediments that originate by biological processes such as secretion of skeletal materials by marine organisms; only a small portion is actually organic matter; most is biologically produced inorganic matter, like skeletal remains of both microscopic and macroscopic organisms; second most abundant in volume and mass; calcareous oozes in the warm, shallow areas above the CCD; siliceous oozes in the colder regions with higher surface activity and below CCD

Turbidity currents

short-lived, gravity induced currents consisting of sediment and water which flow downslope; if enough sediment accumulates and becomes oversteepened, then it will slump and slide downhill in turbidity currents; primary means through which terrigenous sediment is transported from shallow water into the deep sea floor; gets sediments from shelf and slope to the rise and abyssal plains; often triggered by Earthquakes, such as the Grand Banks Earthquake off the coast of Newfoundland

siliceous oozes

silicon dioxide; the biogenic form of silica is opal, while the inorganic form is quartz; opal contains significant amounts of water bound up in its structure; biogenous sediment; controlled by the preservation of biogenic opal, which is preserved in sea water only when buried; found only underneath regions of high surface productivity where biogenic opal accumulates rapidly enough to bury itself before it dissolves; found in Antarctic divergence, upwelling Equatorial regions, and in North Pacific where old, nutrient rich deep waters upwell; diatoms and radiolarians

Carbonate Compensation Depth

solubility of calcium carbonate varies in seawater; CCD is the depth at which rate of dissolution of calcium carbonate is equal to its rate of accumulation; depth of CCD controlled by temperature, pressure, local chemistry, and biological productivity; concentration of CO2 higher in colder, deeper waters, and the higher then concentration of CO2, the faster the calcium carbonate dissolution

Submarine Canyons

steep-walled, V-shaped valleys that incise into continental shelves and slopes and open out at depth on the continental rise; serve as conduits for turbidity currents; associated with the mouths of large rivers; mouths of submarine canyons have large lobes of sediment called submarine fans; smaller submarine canyons soon on the shelf of Pacific US

ocean-continent convergence

subduction of denser ocean plate under continental plate; formation of deep ocean trench adjacent to the continent with a chain of volcanic mountains of continent; e.g. Andes, Cascade in Oregon and Washington

ocean-ocean convergence

subduction of older, denser, cooler ocean plate under younger, warmer, less dense ocean plate; forms deep ocean trenches and associated volcanic island arcs; e.g. Aluetians, Puerto Rico-lesser Antilles, and Tonga

Antarctic Circumpolar Current

subpolar current; largest and strongest current in all the oceans; so well developed it influences circulation all the way to the ocean floor and is primary connection between Atlantic, Pacific, and Indian ocean basins

isopycnals

surfaces of equal density

residence time

the average amount of time an atom or ion of an element remains dissolved in the ocean; assume the ocean is in a steady state with its sources and sinks of different elements or that average amount of element doesn't change over time; residence time is the total amount of the dissolved element in the ocean divided by the flux of the element in or out of the ocean; in units of time

ekman transport

the net transport of wind-driven currents is at an angle (up to 90 degrees) to the prevailing wind; in northern hemisphere, currents deflect to the right (clockwise); in the southern hemisphere, currents deflect to the left (counter-clockwise)

subduction

the process by which lithospheric material is destroyed as one lithospheric plate is forced below another; occurs at regions where plates converge, visible on the sea floor as deep ocean trenches; one consequence is the generation of magma arcs; heat flow is low in trenches but high at adjacent magmatic arcs

continental margins

the zone of the ocean that separates the thin oceanic crust from the thick continental crust; shelf and slope are part of all types of margins; generally composed of sediments

turbidites

these are the deposits of terrigenous sediments that accumulate in submarine basins and slump down to the continental rises and abyssal planes due to turbidity currents; very common

plate boundaries

three types of interactions between plates: divergence at mid-ocean ridges, convergence at ocean trenches, and transform faults

extrapolation

using lines that are defined by data to predict points outside the range of plotted points

interpolation

using lines thats are defined by data to predict points between the data

vertical exaggeration

vertical scale is stretched out relative to the horizontal scale; amount of vertical exaggeration; vertical scale divided by horizontal scale; it is unit-less, but you must make sure that the vertical scale and the horizontal scale are in the same units

volcanogenic sediment

volcanic debris deposited near sites of volcanism, such as near convergent-margin volcanic arcs, or around hot spot volcanoes like Hawaii

western boundary currents

warm currents that flow away from the equator towards high latitudes where they are deflected but the coriolis effect and driven by westerlies to form an east flowing current

surface circulation

water at the surface is primarily driven by wind; top layers of water drag on surfaces beneath them to currents

Passive margins

wide, gently sloping continental shelf (0.1 degrees) followed by a steeper continental slope (4 degrees) and continental rise at the base of the slope (.2 degrees) formed by the accumulation of sedimentary materials; most common in the Atlantic, but occurs in other oceans; no plate boundary; low degree of tectonic activity

photic zone

zone where photosynthesis outdoes respiration; ranges from 100 to 300 m in the open ocean; where most plankton live

foraminiferans

zooplankton which contribute to deep sea oozes; have tests of calcium carbonate; e.g. globigerina; calcareous ooze and biogenous sediment; capture food with fine strands which branch with each other to form a dynamic net

radiolarians

zooplankton which contribute to deep sea oozes; have tests of silicon dioxide; siliceous ooze and biogenous sediment; regulate buoyancy with low density fats and spiny exteriors which increase surface area to help counter sinking