INTRO OCEANOGRAPHY OCS 1005
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Date Created: 10/13/15
OCS MIDTERM CHAPTER 5 SEDIMENTS Sediments are loose accumulations of particular material Their depth and composition tell us relatively recent events in the ocean basin Most abundant terrigenous land amp biogenous once living things Volume of terrigenousgt biogenous Area of Biogenousgt terrigenous Marine sediments are uplifted and exposed on land ie Grand Canyon Rarely older than 180 million years 51 J39 varv greatlv in appearance They originate from the weathering and erosion of rocks from the activity of living organisms volcanic eruptions chemical processes with water from space Sand sediment Sediments of biological origin white ir cream colored high in silica and tending towards grey 52 J39 mav be classi ed bv particle size The smaller the particle the easier it moves Type of particles Diameter Boulder gt 256 mm 10 inches Cobble 64 256 mm Pebble 464 mm Granula 24 mm Sand 0062 2 mm Silt 0004 0062 mm Clay lt 0004 mm Sorting is a function of the energy of the environment The exposure of that area to the action of waves tides and currents Well sorted sediments occur where energy uctuates within narrow limits ie sediments ofthe calm deep ocean oor mix of rubble at the base of a rapidly eroded shore cliff 53 J39 mav be classi ed bv source Classi cation of marine Poorly sorted sediments occur where energy uctuates over a wide spectrum ie the Classi cation was created by Sir John Murray and Af Renard challenge expedition by source of particles Sediment 0f ocean Sources Example Distribution oor type covered dominant in eros1on of land quartz sand 45 cont1nental margins Terr1genous volcanmc eruptlons clay estuary dom1nate abyssal pla1n polar blown dust mud in volume ocean oors organ1c accumulation dommam mi ileep 55 calcareous and ocean oor s111ceous Biogenous of hard parts of some dom1nate s111ceous oozes ooze below about 5 mar1ne organ1sms in area kms rec1 1tation of Man anese p p g present With other dissolved m1nerals nodules 0 Hydrogenous more dominant l A from water often phosphor1te sed1ments from bacteria depos1ts dust from space and tektite spheres mlxedm very small 0 Cosmogenous proportions With more 1 A meteorite debris glassy nodules dominant sediment A Terrigenous sediments o The most abundant o The rocks on Earth s crust are made up of minerals o The texture of igneous rocks is determined by how rapidly they cool not have a chance to form encountered crystals The sediment cycle Granite most familiar continental igneous rock Quartz and clay are the two most common components Slower cooling produces most commonly encountered crystals Nearly all terrigenous sediments are derived directly or indirectly from most commomnly Igneous that cool off rapidly such as basalt solidify so quickly that obvious crystals do erosion gt transport gt deposition gt lithospheric plate gt sedimentary beds gt uplift l Mountains rise as plates collide fuse and subduct N The mountains erode The resulting sediments are transported to the sea by wind and water where they collect on the sea oor 4 The sediments travel with the plates and are either uplifted or subducted 15 billion metric tons are transported in rivers to sea every year E 100 million metric tons transport from land to ocean as ne airborne dust and volcanic ash B Biogenous sediments from the remaining of marine organisms Second most abundant marine sediments Siliceous silicon containing and calcareous calcium carbonate containing sediments makeup of these sediments originally brought to the ocean in solution by river or dissolves in ocean at oceanic ridge extracted from seawater by normal activities of tiny plants and animals to build protective shells and skeletons some derived from mollusk shells stationary colonial animals corals but most are derived from plankton most abundant where ample nutrients encourage high biological productivity near continental margins and areas of up welling over millions of years ago organic molecules within these sediments can form oil and natural gas C Hydrogenous sediments directly from seawater Sources include submerged rock and sediment leaching of the fresh crust at oceanic ridges material issuing from hydrothermal vents and substances owing to the ocean in river run off The most prominent sediments are manganese nodules which litter some deep seabed and phosphorite nodule seen along some continental margins Also called authigenic sediments because they the form in place where they stay Usually accumulate very slowly except for some occasions like rapidly drying lake D Cosmogenous Sediments extraterrestrial origin The least abundant Come from sources of interplanetary dust that falls constantly into the top atmosphere and rarely by impacts of large asteroids and comets Interplanetary dust most dissolves in sea water before reaching the ocean oor Tektiles form from violent impacr of large meteors or small asteroids in the crust of Earth Do not dissolve easily E Marine sediments usually from combinations of sediments Most deposits are mixtures of biogenous and terrigenous particles with an occasional hydrogenous or cosmogenous supplement pattern and composition Great interest to researchers studying condition in the overlying ocean Different marine environments have characteristic sediments which preserve a record of past and present conditions within those environments Continental shelf sediments called neritic sediments consist primary of terrigenous material Deep ocean oors are covered by ner sediments and greater proportion of biogenous 54 Neritic sediment overlie continental margins Eroded from land and carried to streams where transpoted to ocean Currents distribute sand and large particles along the coast Waves carry silts and clay to deeper water Ideally large grains are near the coast and relatively small grains are near the shelf break As an exception larger particles may be moved towards the shelf edge when sea level is low or in ice age Poorly sorted sediments are found as glacial deposits Turbidity currents disrupt the orderly sorting on the continental margin During ice age near the mouths of large rivers 1 meter of sediment may accumulate every thousand years Lithification sediments converted into sedimentary rock by pressure or cementation quot39 and thickness 55 Pelagic varv in Atlantic ocean 1 km of sediments Pacific oor 05 kms of sediments Reasons for difference gt Atlantic ocean is fed by a greater number of rivers laden with sediment than pacific and the Atlantic is smaller in area Pacific ocean has many oceanic trenches that trap sediments towards basin center Turbidities are deposited on the seabed by turbidity propelled by gravity Cuts submarine canyons Can reach continental rise and often abyssal plain The resulting deposits are called turbidito P3 0 U Clays are the nest and most easily transported terrigenous sediments 38 of deep seabed is covered by clays and other ne terrigenous sediments Oozes form from the rigid remains of living creatures Greater proportion of biogenous sediments are further from coastland because les terrigenous material is far from shore Deep ocean sediment containing at least 30 biogenous material are called ooze The organism that contribute their remains to form ooze are small single celled drifting plantlike organisms and the single celled animal that feed on them The silica rich residues give rise to siliceous ooze and the calcium contains material to calcerous ooze These residues accumulate slowly but collect ten times more quickly than clay Accumulation depends on a delicate balance between the abundance of organisms at the surface the rate at which they dissolve once they reach the bottom and the rate of accumulation of terrigenous sediments Calcareous ooze forms mainly from shells of the amoeba like foraminifera small drifting mollusks called pterapods and tiny algae known as coccolithophores CCD calcium carbonate compensation depth Below ccd no calcareous sediments ooze accumulate because it dissolves About half of the surface of deep ocean basins is covered by calcareous ooze while siliceous ooze predominates ate greater depths and in colder polar regions Siliceous ooze is formed from hard parts of another amoeba like animal glassy radiolarian and from single celled algae called diatoms Diatoms are common in deep ocean basins surrounding Antarctica because strong ocean currents and seasonal upwelling in this area support large populations of it Radiolarian ooze occurs in equatorial regions and west of South America Hydrogenous materials precipitate out of seawater itself Hydrogenous materials accumulate in deep sea water and are rarely associated with sediments themselves They originate from chemical reactions occurring on particles of the dominant sediment The most famous hydrogenous material are manganese nodules discovered by HMS challenger in South Africa They consist primarily of manganese and iron oxides but also contain small amounts of cobalt nickel chromium They often form around nuclei such as shark teeth bits of bone microscopic algae animal skeletons and tiny crystals Bacteria activity may play a role in their development 2050 of the Paci c oor may be strewn with nodules 7391 Phosphorus is an important ingredient in fertilizers and someday collected as a a source of agricultural phosphate found only in areas with low rates of sediment accumulation Powdery deposits of metal sul de are found in oceanic edges Evaporites precipitate as seawater evaporates Evaporites are Important group of hydrogenous deposits that include many salts important to humanity They form in the Gulf of California Red Sea and Persian Gulf Carbonates are the rst to precipitate as water salinity increases Calcium sulfate gypsum is next Oolite sands form when calcium carbonate precipitates from seawater Small decrease in the acidity of seawater or increase in temperature can cause calcium carbonate to precipitate from water of normal salinity In shallow areas microscopic plants use up dissolute carbon dioxide making seawater slightly less acidic Oolite sands are abundant in many warm shallow waters 56 Scientists use sensitive tools to study ocean Deep water cameras photograph bottom sediments Clamshell sampler used to take shallow sampler Piston cor take deeper samples CHAPTER 5 VOCAB o Sediment 0 Well sorted sediments o Poorly sorted sediments 0 Minerals 0 Igneous rocks 0 Hydro genous o Microtextites o Pelagic sediments o Turbidities 0 CCD o Oolite sands o Stratigraphy o Paleorenography Pgt CHAPTER 6 WATER AND OCEAN STRUCTURE 62 The water molecule is held together bv chemical bonds Pure water is a compound Water H20 molecule composed of hydrogen and oxygen Chemical bonds are formed when electrons are short between atoms or moved from one atom to another Covalent bonds hold together many familiar molecules besides water like C02 carbon dioxyde and CH4 methane gas and O2 atmospheric oxygen The overall geometry of the water molecule is a bent or angular chape 105 and it is electrically assymetrical Each molecule has positive and negative ends so it behaves as a magnet Water is called a polar molecule Water can easily dissolve many compounds because the polar water molecule will separate that compound component elements from each other Polar nature also permits it to attract other water molecules When a hydrogen atom in one water molecule is attracted to the oxygen atom of an adjacent water molecule a hydrogen bond forms Hydrogen bond link water molecules together by electrostatic fog Cohesion gives water an unusual high surface tension which results in a surface skin capable of supporting needles razor blades and even walking insects Adhesion enables water to adhere to solids to make them Hydrogen bonds give pure water its pale blue hue If hydrogen bonds didn t hold water particles together it would form a gas rather than liquid H2S hydrogen sulfide Is similar to water but gas 63 Water has unusual thermal characteristics The most important characteristic of water is its behavior as it absorbs or loses heat Heat and temperature are not the same thing Water molecules vibrate more rapidly in hot temperature Heat how many and how rapidly molecules are vibrating Temperature measured in degrees US US Not all substances have the same heat capacity Not all substances respond to identical inputs of heat by rising in temperature the same number of degrees Heat capacity is measured in calories gram Because of hydrogen bonds more energy is required to speed up molecular movement and raise water temperature than any other water bond Water can absorb large amounts of heat while changing relatively little in temperature Water s temperature affects its density Density massvolume Density relations are linear Water becomes less dense when it freezes Ice is less dense than liquid crystal and has an hexagon pattern Sensible heat loss not measurable by thermometer Lattent heat of fusion Water removes heat from surfaces as it evaporates latent heat of vaporization Seawater and pure water have slightly different thermal properties Seawater 965 pure water35 dissolved solids and gases Seawater evaporates slower than fresh water Latent heat of evaporation is the same Temperature and salinity affect the density of water 64 Surface water global Ex Thermostatic properties are those properties that aid to moderate changes in termperature Thermal inertia is the tendency of a substance to resist a change in temperature with the gain or loss of heat energy Annual freezing and thawing of ice moderate Earth temperature Movement of water vapor from tropics to poles also moderates earth temperature Why don t the polar oceans freeze solid and equator boil Currents in the atmosphere and ocean are moving huge amounts of heat from the tropics towards poles Ocean surface conditions depend on latitude temperature and salinity 03 0 gt 65 The ocean is stratified by density Liter of seawater weights 2 and 3 more than pure water Density is 1020 Cold salty water is more dense than warm while less salty water and seawater s density increases with increasing salinity pressure and decreasing temperature The ocean is stratified into 3 density zones by temperature and salinity There are 3 zones surface zone mixed layer upper layer of oceanwith constant temperature Water masses have characteristic temperature salinity and density Watermass body of water with characteristic temperature and salinity and therefore density It originates at the ocean surface The pycnocline isolates 80 of the world s ocean water from the 20 involver in surface circulation Density stratification usually presents vertical water movement 66 Refraction can bond the paths of light and sound through water Refraction is the bending of wavy light and sound both wave phenomena Water refracts light Refractive index is the degree in which light is refracted from on medium to another 67 Light does not travel far through the ocean light is a form of electromagnetic radiation or radiant energy that travels as waves through space air and waves visible spectrum light is light we see with our eyes radiowaves infrared ultraviolet X ray short length blue long length red only blue and green pass through water The photic zone is the sun lit surface of the ocean Scattering happens as light is bonded between air or water molecules dust particles water droplets 03 Pgt 03 The absorption of light is governed by the structure of the water molecules it happens to strike When light is absorbed molecules vibrate and light converts into heat Photic zone is the clearest tropical water and most of the ocean life is found here Aphotic zone is a zone of dark water beneath the photic zone Water transmits blue light more efficiently than red Red sea cyanobacteria 68 Sound travels further than light through the ocean Sound is a form of energy transmitted by rapid pressure changes in an elastic medium Marine animals use sound rather than light to see in the ocean Speed of sound 1500 miles per second There s a higher sound speed at the bottom Refraction causes sofar layers and shallow zones Sofar layer is a minimum velocity layer Shadow zone is a region which vary little sound energy penetrates Sonar systems use sounds to detect underwater objects Active sonar projection and return through water of short pulses of high frequency sound to search for objects in the ocean Side scan sonar is a type of active sonar Passive sonar just listen CHAPTER 7 OCEAN CHEMISTRY gt 71 Water is a powerful solvent Water is a solution made of solvent liquid which always contain the more abundant constituents and the solute often dissolves solid or gas and is less abundant Mixture of different substances are closely intermingled but retain separate identities heterogeneous NaCl is held together by ionic bonds Oil non polar Seawater is a complex solution of ions and non ionic solutes Seawater can move through still water my diffusion which is the random movement of minerals through a solution When no more dissolves water is said to be saturated with the substance Saturation is the rate at which molecules of the solute are being dissolved equals the rate at which they are precipitation reforming into crystals at another location in the solution 72 Seawater consists of water and dissolved solids By weight seawater is 965 and 35 is dissolved substance Most salts The ocean contains 5000 trillon kilograms of salt Salinity is ameasure of seawaters total dissolved inorganic solids Salinity is the total quantity of dissolved inorganic solids in water Depending on evaporation precipitation and fresh water run off from continent Average 35 Sodium and chloride are the most abundant Heat capacity decreases when salinity increases and salinity increases when freezing point of water decreases Seawater evaporates slowly Osmotic pressure is the pressure exerted in a biological membrane when the salinity of the environment is different from that within the cells A few ions account for most of the ocean s salinity Oxygen hydrogen 99 residual material Sodium and chloride 85 Trace elements present in amounts less than 00010 U Q The components of ocean salinity came from and have been modi ed by earth s crust Excess volatiles are the components of ocean water whose proportions are not accounted for by the weathering of surface rocks Upper mantle The ratio of dissolved solids in the ocean is constant Georg Forchhamer salinity is constant 5504 of solids will be chloride ions This constant ratio is known as Forcjj ammis principle Salinity is calculated from chlorinity Chlorinity measures the toal mass of halogen ions A salinometer measures the electrical constructivity of seawater The ocean is in chemical equilibrium Chemical equilibrium is the proportion and amount of dissolved salts per unit volume of ocean Steady state ocean Residence time is the average length of time an atom of element spends in the ocean Rt amount of element in the ocean rate at which the element is added to the ocean Mixing time 1600 Seawater constituents may be conservative or non conservative Conservative constituents are constituents of seawater that occur in constant proportion or change slowly through time They have long residence time Example inert gas dissolved in the ocean Non conservative constituents are tied to biological or seasonal cycles or to very short geological cycles They have short residence time Example dissolved oxygen carbon dioxide silica and calcium Aluminum 600 years ago very rare in seawater 73 Gases dissolve in seawater Major gases found in the sea are nitrogen oxygen carbon dioxide Gases dissolve in cold water gt O O Nitrogen is the most abundant gas dissolved in seawater 48 nitrogen Upper layers of ocean are saturated with nitrogen gas Gas concentrations vary with depth Carbon dioxide concentration increases with depth Oxygen concentration decreases through middle depth and increases towards bottom Oxygen levels are higher in deeper water 74 The ocean s acid base balance varies with dissolved and depth An acid is a substance that releases a hydrogen ion in solution A base is a substance that combines with a hydrogen ion in solution Base alkaline solution measured in PH scale Scale acidiclt 7lt alkaline In water solutions some carbonic acid breaks down to produce the hydrogen H ion the bicarbonate HCO3 ion and the carbonate CO32 ion CHAPTER 8 CIRCULATION OF THE ATMOSPHERE wgt 81 The 39 and ocean ineract with each other The atmosphere is the volume of gases water vapor and airborne particles enveloping the earth Intertwined Gases entering the atmosphere from the ocean have effects on climate Vice versa in uence sediment deposition Water evaporated form the ocean syrface and moves by wind the mass movement of air helps minimize worldwide extremes of surface temperatures through rain and provides moisture for agriculture weather shaped by wind and water Flow of air in uences the movements in water Weather is the state of the atmosphere at a speci c time or place Climate is the longterm statistical view of weather in an area 82 The 39 is J mainlv of nitrogen oxvgen and water vapor The lower atmosphere is a nearly homogenous mixture of gases Nitrogen 781 Oxygen 209 Other vompounds 1 Tresidence time of water vapor is 10 days Water leaves the atmosphere by condensing into dew rain snow Air has mass 1 square cm column of dry air from sea level to the top of the atmosphere weights 104 kg Warm air is less dense than cool air Humid air is less dense than dry air Warm air can hold more water vapor than cold air Atmosphere loses water as precipitation 83 The 39 51 of incoming energy is absorbed by earths land and water surface moves in response to uneven solar heating and earth s rotation How much light penetrates the ocean depends on the angle at which it approaches the sea state surface turbulence the presence of an ice covering or light colored foam etc Earth is a headt budget total income heat otal heat radiating into the cold of space Earth is in thermal equilibrium it is growing neither significally warmer nor colder The solar heating of earth varies with latitude The solar heating of earth varies with the seasons Mid latitude heating is strongly affected by the change of seasons Earth s uneven heating results in largescale atmosphere circulation A convection current is the circular current of air in a room caused by the difference in air density resulting from the temperature differences between the ends of the room Global circulation of air is governed by 2 factors Uneven solar heating Earth s rotation Coriolis effect the eastward rotation of earth on its aXis de ects the moving air or water away from its initial course The Coriolis effect de ects the path of moving objects Tour around he world 360 grades The Coriolis effect in uences the movement of air in atmosphere circulation cells Atmospheric circulation cell is a large circuit of air that begins to rise as it approaches the equator and completes the circuit We got these cells in the moon Hadley cells are pairs of cells that exist in the tropics one on each side of the equator The mid latitude circulation cells of each hemisphere are Ferrel cells Latitude turns poleward tom complete a circuit these cells are polar cells 84 39 ic 39 39 quot generates large scale surface wind patterns The equatorial low is called the doldrums Scientists call this area the intertropical convergence zone ITCZ Horse latitudes are areas of high atmospheric pressure and little surface wind Trade winds are the most constant surface winds between the zones of ascending and descending air winds of Hadley cells Westerlies are surface winds of the Ferrel cells A Cell circulation centers on the metereological not geographical equator Geographical equator 0 latitude Metereological equator thermal equator at 5 latitude B Monsoons are wind patterns that change With the seasons C Sea breeze and land breeze arise from uneven surface heating 0 Sea breeze is cooler air from over the sea that moves towards land 0 Land breeze is breeze in reverse direction of sea breeze 85 Storms are variations in large scale atmosphere circulation o Storms are regional atmospheric disturbances characterized by strong winds often accompanied by precipitation o Cyclones are huge rotatin masses of low pressure air in which wind converge and ascend o A tornado is a much smaller funnel of fast spinning wind
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