1. 1 Distribution of sediments on the sea floor Distribution of sediments on the sea floor Seabed Resources Seabed Resources Sediments are particles of organic or inorganic matter that accumulate in a loose, unconsolidated form. Record of geologic/oceanographic history Types (Classification) Types (Classification) Location or distribution of sediments Location or distribution of sediments Rates of Deposits/Accumulation Rates of Deposits/Accumulation Chapter 5 - Sediments

2. 2 Sediment Classification Particle Size (Grain Size) Particle Size (Grain Size) Location (where the grains are deposited) Location (where the grains are deposited) Source and Chemistry Source and Chemistry

3. 3 Large (L) Medium (M) Small (S) Grain Size Classification

4. 4 Sediments May Be Classified By Particle Size The velocities of currents required for erosion, transportation, and deposition (sedimentation) of sediment particles of different sizes. To dislodge and carry a particle of size A, the speed of a current must exceed 20 centimeters per second (8 inches per second). When the current falls below 1 centimeter per second (1/2 inch per second), the particle will be deposited.

5. 5 Sediment can be classified by particle size. Waves and currents generally transport smaller particles farther than larger particles. How far sediments go horizontally and how long it takes to get to bottom of sea depends on size. Shape is also important to how sediments go around and settle in the bottom. L M S

6. 6 Poorly SortedWell Sorted well sorted: uniform grain size poorly sorted: variable grain size

7. 7 Bluff Erosion Offshore Glacially Deposited Sand Ridges, Relict Ebb Shoals Sources of Sand For Littoral Transport 2 m Tide Dominated & Riverine Wave Dominated Mixed Energy Gravel Sand Barrier Island Cliff or Bluff Coast

8. 8

9. 9 Littoral Transport reaches a maximum rate of 463,015 to 601,657 yd 3 /yr at Democrat Point (Fire Island Inlet)

10. 10 Classification Based on Location (where sediments are found) Neritic: near continental margins & islands Pelagic: deep sea floor

11. 11

12. 12 Marine Sediments Are Usually Combinations of Terrigenous (from rocks) and Biogenous (organic) Deposits The sediment of continental shelves is called neritic sediment, and contains mostly terrigenous material. Sediments of the slope, rise, and deep-ocean floors are pelagic sediments, and contain a greater proportion of biogenous material.

13. 13 Classification Based on Source & Chemistry Type Source Terrigenous pre-existing rock (or Lithogenous) all land derived material Biogenousliving organisms Hydrogenousprecipitation from sea water Cosmogenousspace

14. 14 Lithogenous From rocks, wood, waste sludge, volcanic stuff Results from erosion by air & water Transported by winds, water, ice and gravity. Also by glaciers and icebergs dominates the neritic sediments because it is the largest source for thesedominates the neritic sediments because it is the largest source for these Pelagic lithogenous sediments  abyssal clay (about 75% of clay), very slow accumulation, rich in Fe  red clayPelagic lithogenous sediments  abyssal clay (about 75% of clay), very slow accumulation, rich in Fe  red clay

15. 15 Biogenous Oozes – sediment containing at least 30% biogenous material. Dominant on deep-ocean floor, 2 types of oozes: * Calcareous (CaCo 3 ) oozes formed by organisms which contain calcium carbonate in their shells or skeletons – dominant pelagic sediment (cocolithophorids, pteropods, foraminifera) * Siliceous (SiO 2 ) oozes formed by organisms that contain silica in their shells. Diatoms are one type of organism whose remains contribute to siliceous oozes. The ocean is under-saturated with respect to Si, so it can dissolve everywhere. (large contribution from photosynthetic organisms)

16. 16 The line shows the calcium carbonate (CaCO 3 ) compensation depth (CCD). At this depth, usually about 4,500 meters (14,800 feet – about the height of some of the peaks in the Colorado Rocky Mountains, known as ‘the fourteen- ers’ ), the rate at which calcareous sediments accumulate equals the rate at which those sediments dissolve. CCD (~4500 meters) depth where rate of dissolution of calcium carbonate is equals to its rate of accumulation Calcareous Oozes

17. 17 Originate from chemical reactions with water that occur in the existing sediment. Hydrogenous sediments are often found in the form of nodules containing manganese and iron oxides. Hydrogenous sediments can be: Carbonates  direct deposition Phosphorites  abundant in continental shelf Salts  by evaporation Evaporites - salts that precipitate as evaporation occurs. Evaporites include many salts with economic importance. Evaporites currently form in the Gulf of California, the Red Sea, and the Persian Gulf Manganese nodules  Mn, Fe, Cu, Ni, Co. These are found in abyssal seafloor and continental margins, around ocean ridges and seamounts (but at higher concentrations than those found on land). The Co (cobalt) content is of strategic importance to US (used in aircraft’s manufacture). Hydrogenous

18. 18 Hydrogenous Lithogenous (or terrigeneous) (abbyssal clay, red clay Fe)

19. 19 Map of distribution of sediment The general pattern of sediments on the ocean floor. Note the dominance of diatom oozes at high latitudes. What differences in the type and distribution of sediments do you note between the Atlantic Ocean and the Pacific Ocean?

20. 20 Compare: Neritic Sediments Neritic Sediments 1.Rivers 800,000 cm/1000 years 2.Bays 500 cm/1000 years 3.Shelf 40 cm/1000 years Pelagic Sediments Pelagic Sediments 1 cm/1000 years! 1 cm/1000 years!

21. 21 Sand and Gravel  construction Sand and Gravel  construction Phosphorite  fertilizers Phosphorite  fertilizers Sulfur  sulfuric acid for industry Sulfur  sulfuric acid for industry Coal  energy Coal  energy Oil and Gas  energy, transportation Oil and Gas  energy, transportation (20-25% of US production comes from offshore areas) Maganese Nodules  Mn, Fe, Co, Cu, Ni Maganese Nodules  Mn, Fe, Co, Cu, Ni Gas Hydrates  energy in the future? Gas Hydrates  energy in the future? Resources

22. Chapter 6 Water and Ocean Structure Some basic concepts: Compounds – substances that contain two or more different elements in fixed proportions Element – a substance composed of identical particles that cannot be chemically broken down into simpler substances Atoms – the particles that make up elements

23. 23 A water molecule is composed of two hydrogen (H) atoms and one A water molecule is composed of two hydrogen (H) atoms and one oxygen atom (O 2 ). oxygen atom (O 2 ). A molecule is a group of atoms held together by chemical bonds. A molecule is a group of atoms held together by chemical bonds. Water is a polar molecule, having a positive and a negative side. Water is a polar molecule, having a positive and a negative side. Chemical bonds, the energy relationships between atoms that hold them Chemical bonds, the energy relationships between atoms that hold them together, are formed when electrons - tiny negatively charged particles together, are formed when electrons - tiny negatively charged particles found toward the outside of an atom - are shared between atoms or found toward the outside of an atom - are shared between atoms or moved from one atom to another. moved from one atom to another.

24. 24 H2OH2O Covalent bonds: shared pairs of electrons Hydrogen bonds: bonds between water molecules due to polar structure

25. 25 Hydrogen bonds form when the positive end of one water molecule bonds to the negative end of another water molecule. Two important properties of water molecules: Cohesion – the ability of water molecules to stick to each other, creating surface tension. Adhesion – the tendency of water molecules to stick to other substances Hydrogen Bonds

26. 26 Temperature, Heat, Heat Capacity, Calories, etc. Temperature Measure of av. kinetic energy (motion) of molecules (KE=1/2mv 2 ) Measure of av. kinetic energy (motion) of molecules (KE=1/2mv 2 ) unit is degrees C, F or K (Kelvin) unit is degrees C, F or K (Kelvin)Heat Measure of the total kinetic energy of the molecules in a substance Measure of the total kinetic energy of the molecules in a substance Unit is the calorie Unit is the calorie * Heat Capacity = is a measure of the heat required to raise the temperature of 1g of a substance by 1  C. * Calorie = amount of heat to raise temperature of 1 gram of pure water by 1°C (from 14.5 °C to 15.5 °C) * Latent Heat

27. 27 Not All Substances Have the Same Heat Capacity Water has a very high heat capacity, which means it resists changing temperature when heat is added or removed – large thermal inertia

28. 28 Remember from Chapter 3? Density is a key concept for understanding the structure of Earth – differences in density lead to stratification (layers). Density measures the mass per unit volume of a substance. Density = _Mass_ Volume Density is expressed as grams per cubic centimeter. (pure) Water has a density of 1 g/cm 3 Granite Rock is about 2.7 times more dense just about everything in this course! Temperature affects water’s density

29. 29 The relationship of density and temperature for pure water. Note that points C and D both represent 0°C (32°F) but different densities and thus different states of water. Ice floats because the density of ice is lower than the density of liquid water.

30. 30 Governed by molecular processes Governed by molecular processes Addition of heat: breaks H bonds first, then temperature rises Addition of heat: breaks H bonds first, then temperature rises Removal of heat: H bonds form, Energy releases as heat, prevents a rapid temperature drop Removal of heat: H bonds form, Energy releases as heat, prevents a rapid temperature drop Polarity(+/-): keeps molecules together Polarity(+/-): keeps molecules together Behavior of Water

31. 31 Changes of State-due to addition or loss of heat (breaks H bonds) The amount of energy required to break the bonds is termed the latent heat of vaporization. Water has the highest latent heat of vaporization of any known substance.

32. 32 * melting/evaporation requires addition of heat: 80 and 540 calories, respectively. For 1 gram of H 2 O * condensation/freezing release heat to the environment: 540 and 80 calories, respectively.

33. 33 Things to remember: 1. Can have liquid water at 0°C and below (supercooled water) 2. Can change directly solid to gas - sublimation 3. Can boil water at temperature below 100°C (if pressure decreases as when at the top of a high mountain) 4. Evaporation removes heat from Earth’s surface (it is a cooling mechanism) 5. Condensation in atmosphere releases heat that will drive Earth’s weather cycle

34. 34 Adding salt to pure water  Seawater 96.5% of pure water and 3.5% dissolved material  Seawater

35. 35 I. add salt to water and observe 1. decrease freezing point (increase boiling point) 2. not much change in heat capacity & latent heats 3. increase surface tension (cohesion) 4. increase (of course) in density II. increase temperature and observe 1. decrease in seawater density (very sensitive to T) 2. decrease in surface tension III. but changes in pressure are mostly ignored by physical properties of water - seawater is nearly incompressible

36. 36 Fig. 6-10, p. 164 San Francisco Norfolk Temperature (°F) San Francisco Norfolk Temperature (°C) Surface Water Moderates Global Temperature

37. 37 Fig. 6-14, p. 167 Tropic of Cancer Equator Tropic of Capricorn Salinity Temperature Latitude North South Ocean-Surface Conditions Depend on Latitude, Temperature, and Salinity

38. 38 Fig. 6-17, p. 169 The Ocean Is Stratified by Density two samples of water can have the same density at different combinations of temperature and salinity!

39. 39 The Ocean Is Stratified into Three Density Zones by Temperature and Salinity a.The surface zone or surface layer or mixed layer b.The pycnocline, or thermocline or halocline c.The deep ocean (~ 80% of the ocean is below the surface zone

40. 40 510152025 Polar Tropical 2,000 Temperate 1,000 4,000 6,000 2,000 Depth (m) 8,000 Depth (ft) 3,000 10,000 40506070 Temperature (°F) Temperature (°C) Typical temperature profiles at polar, tropical, and middle (temperate) latitudes. Note that polar waters lack a thermocline.

41. 41 Sound and light in Seawater Sound and light both travel in waves Refraction is the bending of waves, which occurs when waves travel from one medium to another Refraction Can Bend the Paths of Light and Sound through Water Light may be absorbed, scattered, reflected, refracted and attenuated (decrease in intensity over distance) Sunlight does not travel well in the ocean. Scattering and absorption weaken light

42. 42 Form of electromagnetic Form of electromagnetic radiation radiation Seawater transmits visible Seawater transmits visible portion of the electromagnetic portion of the electromagnetic spectrum (water transmits blue light more spectrum (water transmits blue light more efficiently than red) efficiently than red) 60% is absorbed by 1 m depth 60% is absorbed by 1 m depth 80% absorbed by 10 m depth 80% absorbed by 10 m depth No light penetration below 1000 m No light penetration below 1000 m Shorter wavelengths (blues) are transmitted to deeper depths Shorter wavelengths (blues) are transmitted to deeper depths Light Refraction: bending of light due to change in density between air and water

43. 43 Water Transmits Blue Light More Efficiently Than Red most of the ocean lies in complete blackness

44. 44 Sound Travels Much Farther Than Light in the Ocean On average: ss in Air = 334 m/s ss in Water = 1500 m/s ss increases as temperature and pressure increase: sound travels faster in warm surface waters and then again in deep (cold) waters where pressures are higher

45. 45 The sofar layer, in which sound waves travel at minimum speed. Sound transmission is particularly efficient - that is, sounds can be heard for great distances - because refraction tends to keep sound waves within the layer. The so(sound)f(fixing)a(and)r(ranging) zone

46. 46 Chapter 7 Ocean Chemistry About solutions and mixtures A solution is made of two components, with uniform (meaning ‘the same everywhere’) molecular properties: The solvent, which is usually a liquid, and is the more abundant component. The solute, often a solid or gas, is the less abundant component. A mixture is different from a solution. In a mixture the components retain separate identities, so it is NOT uniform throughout.

47. 47 Water is a powerful solvent and we have it everywhere – the hydrological cycle

48. 48 Ocean Salinity Salinity is the total quantity of dissolved inorganic solids in water. Salinity is the total quantity of dissolved inorganic solids in water. 3.5% salt on average 3.5% salt on average measured in g/kg (ppt = parts per thousand) measured in g/kg (ppt = parts per thousand) Ocean salinities vary in space Processes that affect salinity: evaporation, precipitation, runoff, freezing, and thawing And recall that: And recall that: The heat capacity of water decreases with increasing salinity As salinity increases, freezing point decreases As salinity increases, evaporation slows (boiling point increases)

49. 49 Mid Ocean Average Surface Salinity

50. 50 Dissolved salts  Major constituents and trace elements  Conservative/nonconservative constituents Major Constituents = [] > 1 part per million Major Constituents = [] > 1 part per million  Na + Sodium  Cl - Chloride  SO 4- Sulfate  Mg 2+ Magnesium  Ca 2+ Calcium  K + Potassium 99 % 86 % Trace Elements = [] < 1 part per million Trace Elements = [] < 1 part per million

51. 51 A few ions (charged particles) account for most of the salinity of the oceans. See Table 7.2 for minor and trace elements in seawater

52. 52 Regulating the major constituents in seawater Sources of salt: Positive ions: weathering and erosion Negative ions: gases from volcanic eruptions Hydrothermal activity supply and remove salt from the deep ocean Balance of salt: Input: rivers, volcanic activity, groundwater, hydrothermal vents and cold springs, and the decay of once- living organisms. Output: sea spray, uptake by living organisms, incorporation into sediments, and ultimately by subduction.

53. 53 The ratio of dissolved solids in the ocean is constant:  Well-mixed solution  Principle of Constant Proportions : the ratios between the concentrations of major between the concentrations of major conservative ions in open-ocean water are conservative ions in open-ocean water are constant constant

54. 54 Seawater’s constituents may be conservative or nonconservative  Conservative = concentration changes only as a result of mixing, diffusion, and only as a result of mixing, diffusion, and advection advection  Non-conservative = concentration changes as a result of biological or chemical changes as a result of biological or chemical processes as well as mixing, diffusion, and processes as well as mixing, diffusion, and advection advection

55. 55 Distribution with depth Distribution with depth  Photosynthesis removes CO 2 and produces O 2 at the surface  Respiration produces CO 2 and removes O 2 at all depths  Compensation depth (Photosynthesis = Respiration) CO 2 O 2 Gases photosynthesis respiration

56. 56 Oxygen and CO 2 profiles CO 2 Concentrations Direct solution of gas from the atmosphere Respiration of marine organisms Oxidation (decomposition) of organic matter O 2 Concentrations Photosynthesis Bottom water enrichment oxygen minimum

57. 57 metric tons C (10 6 ) The Carbon/Carbon Dioxide Cycle - numbers in black = rates of exchange numbers in green = total amounts stored in reservoirs numbers in parenthesis = net annual changes  Ocean uptake from atmosphere Depends on: pH, temperature, salinity, chemistry  Biological pump

58. 58 Seawater Alkaline, pH from 7.5-8.5 Alkaline, pH from 7.5-8.5 Average pH=7.8 Average pH=7.8 pH relatively constant due to buffering action of CO 2 pH relatively constant due to buffering action of CO 2 Buffer = substance that prevents sudden or large changes in the acidity or alkalinity of a solution Buffer = substance that prevents sudden or large changes in the acidity or alkalinity of a solution Important for biological processes Important for biological processes pH inversely proportional to the concentration of CO 2 pH inversely proportional to the concentration of CO 2

59. 59 CO 2 combines readily with seawater to form carbonic acid (H 2 CO 3 ). Carbonic acid can then lose a H+ ion to become a bicarbonate ion (HCO 3- ), or two H+ ions to become a carbonate ion (CO 3 2- ). Some bicarbonate ions dissociate to form carbonate ions, which combine with calcium ions in seawater to form calcium carbonate (CaCO3), used by some organisms to form hard shells and skeletons. When their builders die, these structures may fall to the seabed as carbonate sediments, eventually to be redissolved. As the double arrows indicate, all these reactions may move in either direction. CO 2 Buffer