1 Distribution of sediments on the sea floor Distribution of sediments on the sea floor Seabed Resources Seabed Resources Sediments are particles of organic.

11

• Distribution of sediments on the sea Distribution of sediments on the sea floorfloor

• Seabed ResourcesSeabed 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 sedimentsLocation or distribution of sediments

• Rates of Deposits/AccumulationRates of Deposits/Accumulation

Chapter 5 - SedimentsChapter 5 - Sediments

22

Sediment ClassificationSediment Classification

• Particle Size (Grain Size)Particle Size (Grain Size)

• Location (where the grains are Location (where the grains are deposited)deposited)

• Source and ChemistrySource and Chemistry

33

Large (L)

Medium (M)

Small (S)

Grain Size Grain Size ClassificationClassification

44

Sediments May Be Classified By Particle SizeSediments May Be Classified By Particle Size

The velocities of The velocities of currents required for currents required for erosion, transportation, erosion, transportation, and deposition and deposition (sedimentation) of (sedimentation) of sediment particles of sediment particles of different sizes.different sizes.

To dislodge and carry a To dislodge and carry a particle of size A, the particle of size A, the speed of a current speed of a current must exceed 20 must exceed 20 centimeters per second centimeters per second (8 inches per second). (8 inches per second). When the current falls When the current falls below 1 centimeter per below 1 centimeter per second (1/2 inch per second (1/2 inch per second), the particle second), the particle will be deposited.will be deposited.

55

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

66

Poorly SortedPoorly Sorted Well SortedWell Sorted

well sorted: uniform grain size

poorly sorted: variable grain size

77

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

88

99

•Littoral Transport reaches a maximum rate of 463,015 to 601,657 yd3/yr at Democrat Point (Fire Island Inlet)

1010

Classification Based on Location (where sediments are found)

Neritic: near continental margins & islands Pelagic: deep sea floor

1111

1212

Marine Sediments Are Usually Combinations of Terrigenous (from rocks) and Biogenous (organic) Deposits

The sediment of The sediment of continental continental shelves is called shelves is called neriticneritic sediment, sediment, and contains and contains mostly terrigenous mostly terrigenous material.material.Sediments of the Sediments of the slope, rise, and slope, rise, and deep-ocean floors deep-ocean floors are are pelagicpelagic sediments, and sediments, and contain a greater contain a greater proportion of proportion of biogenous biogenous material.material.

1313

Classification Based on Source & ChemistryType Source

Terrigenous pre-existing rock (or Lithogenous) all land derived material

Biogenous living organisms

Hydrogenous precipitation from sea water

Cosmogenous space

1414

Lithogenous

From rocks, wood, waste sludge, volcanic stuffFrom rocks, wood, waste sludge, volcanic stuff

Results from erosion by air & water Transported Results from erosion by air & water Transported by winds, water, ice and gravity. Also by by winds, water, ice and gravity. Also by glaciers and icebergsglaciers and icebergs

•dominates the neritic sediments because it is dominates the neritic sediments because it is the largest source for thesethe largest source for these

•Pelagic lithogenous sediments Pelagic lithogenous sediments abyssal clay abyssal clay (about 75% of clay), very slow accumulation, (about 75% of clay), very slow accumulation, rich in Fe rich in Fe red clay red clay

1515

Biogenous

Oozes – sediment containing at least 30% biogenous material. Dominant on deep-ocean floor, 2 types of oozes:

* Calcareous (CaCo3) oozes formed by organisms which contain calcium carbonate in their shells or skeletons –

dominantpelagic sediment (cocolithophorids, pteropods,

foraminifera)

* Siliceous (SiO2) oozesformed 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)

1616

The line shows the calcium carbonate (CaCO3) 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

1717

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).

HydrogenousHydrogenous

1818

HydrogenousHydrogenous

Lithogenous (or terrigeneous) (abbyssal Lithogenous (or terrigeneous) (abbyssal clay, red clay Fe)clay, red clay Fe)

1919

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?

2020

Compare:Compare:

• Neritic SedimentsNeritic Sediments

1.1. Rivers 800,000 cm/1000 yearsRivers 800,000 cm/1000 years2.2. Bays 500 cm/1000 yearsBays 500 cm/1000 years3.3. Shelf 40 cm/1000 yearsShelf 40 cm/1000 years

• Pelagic SedimentsPelagic Sediments 1 cm/1000 years!1 cm/1000 years!

2121

• Sand and Gravel Sand and Gravel construction construction

• Phosphorite Phosphorite fertilizers fertilizers

• Sulfur Sulfur sulfuric acid for industry sulfuric acid for industry

• Coal Coal energy energy

• Oil and Gas Oil and Gas energy, transportation energy, transportation

(20-25% of US production comes (20-25% of US production comes from from offshore areas) offshore areas)

• Maganese Nodules Maganese Nodules Mn, Fe, Co, Cu, Ni Mn, Fe, Co, Cu, Ni

• Gas Hydrates Gas Hydrates energy in the future? energy in the future?

ResourcesResources

Chapter 6Chapter 6Water and Ocean StructureWater 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

2323

• 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 (Ooxygen atom (O22).). • A A moleculemolecule is a group of atoms held together by is a group of atoms held together by chemical bonds.chemical bonds.• Water is aWater is a polar molecule, polar molecule, having a positive and a negative side.having a positive and a negative side.• Chemical bonds, the energy relationships between atoms that hold Chemical bonds, the energy relationships between atoms that hold them them together, are formed when together, are formed when electronselectrons - tiny negatively charged particles - 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.

2424

H2O• Covalent bonds: shared pairs of electrons• Hydrogen bonds: bonds between water molecules due to polar structure

2525

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

2626

Temperature, Heat, Heat Capacity, Temperature, Heat, Heat Capacity, Calories, etc.Calories, etc.

TemperatureTemperature

• Measure of av. kinetic Measure of av. kinetic energy (motion) of energy (motion) of molecules (KE=1/2mvmolecules (KE=1/2mv22))

• unit is degrees C, F or unit is degrees C, F or K (Kelvin)K (Kelvin)

HeatHeat

• Measure of the total Measure of the total kinetic energy of the kinetic energy of the molecules in a molecules in a substancesubstance

• Unit is the calorieUnit is the calorie

* Heat Capacity = is a measure of the heat required to raise the temperature of 1g of a substance by 1C.

* 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

2727

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

2828

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/cm3

Granite Rock is about 2.7 times more dense

just about everything in this course!

Temperature affects water’s density

2929

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.

3030

• Governed by molecular processesGoverned by molecular processes

• Addition of heat: breaks H bonds first, Addition of heat: breaks H bonds first, then temperature risesthen temperature rises

• Removal of heat: H bonds form, Removal of heat: H bonds form, Energy releases as heat, prevents a Energy releases as heat, prevents a rapid temperature droprapid temperature drop

• Polarity(+/-): keeps molecules Polarity(+/-): keeps molecules togethertogether

Behavior of Water

3131

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.

3232

* melting/evaporation requires addition of heat: 80 and 540 calories, respectively.

For 1 gram of H2O

* condensation/freezing release heat to the environment: 540 and 80 calories, respectively.

3333

Things to remember:

1. Can have liquid water at 0°C and below (supercooled water) 2. Can change directly solid to gas - sublimation3. 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

3434

Adding salt to pure water

Seawater

96.5% of pure water and 3.5% dissolved material

Seawater

3535

I. add salt to water and observe1. decrease freezing point (increase boiling point)2. not much change in heat capacity & latent heats3. increase surface tension (cohesion)4. increase (of course) in densityII. increase temperature and observe1. decrease in seawater density (very sensitive to T) 2. decrease in surface tensionIII. but changes in pressure are mostly ignored by physical properties of water - seawater is nearly incompressible

3636

San Francisco Norfolk

Tem

per

atu

re (

°F)

San Francisco

Norfolk

Tem

per

atu

re (

°C)

Surface Water Moderates Global Temperature

3737

Tropic of Cancer Tropic of Cancer

Equator Equator

Tropic of Capricorn Tropic of Capricorn

Salinity

Salinity

Temperature

Temperature

Lat

itu

de

No

rth

So

uth

Ocean-Surface Conditions Depend on Latitude, Temperature, and Salinity

3838Fig. 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!

3939

The Ocean Is Stratified into Three Density Zones by Temperature and Salinity

a.The surface zone or surface layer or mixed layerb.The pycnocline, or thermocline or haloclinec.The deep ocean (~ 80% of the ocean is below the surface zone

4040

5 10 15 20 25

Polar

Tropical 2,000

Temperate1,000

4,000

6,0002,000

Dep

th (

m)

8,000 Dep

th (

ft)

3,000 10,000

40 50 60 70

Temperature (°F)

Temperature (°C)

Typical temperature profiles at polar, tropical, and middle (temperate) latitudes. Note that polar waters lack a thermocline.

4141

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

4242

• Form of electromagnetic Form of electromagnetic radiationradiation• Seawater transmits visible Seawater transmits visible portion of the electromagnetic portion of the electromagnetic spectrum (water transmits blue light morespectrum (water transmits blue light more efficiently than red)efficiently than red)• 60% is absorbed by 1 m depth60% is absorbed by 1 m depth• 80% absorbed by 10 m depth80% absorbed by 10 m depth• No light penetration below 1000 mNo light penetration below 1000 m• Shorter wavelengths (blues) are transmitted Shorter wavelengths (blues) are transmitted

to deeper depthsto deeper depths

LightRefraction: bending of light due to change in density between air and water

4343

Water Transmits Blue Light More Efficiently Than Red

most of the ocean lies in complete blackness

4444

Sound Travels Much Farther Than Light in the Ocean

On average:ss in Air = 334 m/sss 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

4545

The sofar The sofar layer, in which layer, in which sound waves sound waves travel at minimum travel at minimum speed. speed.

Sound Sound transmission is transmission is particularly particularly efficient - that is, efficient - that is, sounds can be sounds can be heard for great heard for great distances - distances - because refraction because refraction tends to keep tends to keep sound waves sound waves within the layer.within the layer.

The so(sound)f(fixing)a(and)r(ranging) zone

4646

Chapter 7 Chapter 7 Ocean ChemistryOcean Chemistry

About solutions and mixturesAbout solutions and mixtures

A A solutionsolution is made of two components, with is made of two components, with uniformuniform (meaning ‘the same everywhere’) molecular (meaning ‘the same everywhere’) molecular properties:properties:

The The solvent, solvent, which is usually a liquid, and is the which is usually a liquid, and is the more abundant component.more abundant component.

The The solute, solute, often a solid or gas, is the less abundant often a solid or gas, is the less abundant component.component.

AA mixture mixture is different from a solution. In a mixture is different from a solution. In a mixture the components retain separate identities, so it is the components retain separate identities, so it is NOT uniform throughoutNOT uniform throughout..

4747

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

4848

Ocean SalinityOcean Salinity

• SalinitySalinity is the total quantity of dissolved is the total quantity of dissolved inorganic solids in water.inorganic solids in water.

• 3.5% salt on average3.5% salt on average

• measured in g/kg (ppt = parts per thousand)measured in g/kg (ppt = parts per thousand)

Ocean salinities vary in spaceOcean salinities vary in space

Processes that affect salinity: evaporation, Processes that affect salinity: evaporation, precipitation, runoff, freezing, and thawingprecipitation, runoff, freezing, and thawing And recall that: And recall that:

The heat capacity of water decreases with increasing salinityThe heat capacity of water decreases with increasing salinity

As salinity increases, freezing point decreasesAs salinity increases, freezing point decreases

As salinity increases, evaporation slows (boiling point increases)As salinity increases, evaporation slows (boiling point increases)

4949

Mid Ocean Average Surface Salinity

5050

• Dissolved salts Major constituents and trace elements Conservative/nonconservative constituents

• Major Constituents = [] > 1 part per millionMajor Constituents = [] > 1 part per million

NaNa++ SodiumSodium ClCl-- ChlorideChloride SOSO4-4- SulfateSulfate MgMg2+2+ MagnesiumMagnesium CaCa2+2+ CalciumCalcium KK++ PotassiumPotassium

99 %

86 %

• Trace Elements = [] < 1 part per millionTrace Elements = [] < 1 part per million

5151

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

5252

Regulating the major constituents in seawaterRegulating 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.

5353

The ratio of dissolved solids in the ocean The ratio of dissolved solids in the ocean is constant:is constant:

Well-mixed solutionWell-mixed solution

Principle of Constant ProportionsPrinciple of Constant Proportions : the : the ratiosratios 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

5454

Seawater’s constituents may be Seawater’s constituents may be conservative or nonconservativeconservative or nonconservative

ConservativeConservative = concentration changes = concentration changes

only as a result of mixing, diffusion, and only as a result of mixing, diffusion, and

advectionadvection

Non-conservativeNon-conservative = concentration = concentration

changes as a result of biological or chemicalchanges as a result of biological or chemical

processes as well as mixing, diffusion, and processes as well as mixing, diffusion, and

advectionadvection

5555

• Distribution with depthDistribution with depth

Photosynthesis removes COPhotosynthesis removes CO22 and produces O and produces O22 at the at the surfacesurface

Respiration produces CORespiration produces CO22 and removes O and removes O22 at all depths at all depthsCompensation depth (Photosynthesis = Respiration)Compensation depth (Photosynthesis = Respiration)

COCO22 O O22

Gases

photosynthesis

respiration

5656

Oxygen and CO2 profiles

CO2 Concentrations

Direct solution of gas from the atmosphere

Respiration of marine organisms

Oxidation (decomposition) of organic matter

O2 Concentrations

Photosynthesis

Bottom water enrichment

oxygen minimum

5757

metric tons C (106)

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

5858

SeawaterSeawater

• Alkaline, pH from 7.5-8.5Alkaline, pH from 7.5-8.5• Average pH=7.8Average pH=7.8• pH relatively constant due to buffering action of pH relatively constant due to buffering action of

COCO22

• BufferBuffer = substance that prevents sudden or large = substance that prevents sudden or large changes in the acidity or alkalinity of a solutionchanges in the acidity or alkalinity of a solution

• Important for biological processesImportant for biological processes• pH inversely proportional to the concentration of pH inversely proportional to the concentration of

COCO22

5959

COCO22 combines readily with seawater to form carbonic acid (H combines readily with seawater to form carbonic acid (H22COCO33). Carbonic ). Carbonic acid can then lose a H+ ion to become a bicarbonate ion (HCOacid can then lose a H+ ion to become a bicarbonate ion (HCO3-3-), or two H+ ), or two H+ ions to become a carbonate ion (COions to become a carbonate ion (CO33

2-2-). Some bicarbonate ions dissociate to ). Some bicarbonate ions dissociate to form carbonate ions, which combine with calcium ions in seawater to form form carbonate ions, which combine with calcium ions in seawater to form calcium carbonate (CaCO3), used by some organisms to form hard shells calcium carbonate (CaCO3), used by some organisms to form hard shells and skeletons. When their builders die, these structures may fall to the and skeletons. When their builders die, these structures may fall to the seabed as carbonate sediments, eventually to be redissolved. As the double seabed as carbonate sediments, eventually to be redissolved. As the double arrows indicate, all these reactions may move in either direction.arrows indicate, all these reactions may move in either direction.

CO2 Buffer