Oceanography Exam Part 2

sediments

- used to deduce Earth's history

- overtime lithifies to form sedimentary rock

-settle few cm/ years to thickness of dime every 1000 yrs

Marine Sediments Tell Us

temperatures, nutrient supply, marine life, winds, current patterns, volcanic eruptions, extinction events

Marine Sediment Collection

Dredges, cores, rotary drilling

Paleoceanography

study of how ocean, atmo, and land have interacted to produce changes in the ocean chem, circulation, biology, and climate

How do you process a core?

measure the cores density and porosity, make markers in cores, bio/chem measurements

4 main types of marine sediments

lithogenous, biogenous, hydrogenous, cosmogenous

Lithogenous

sediment from pre-existing rock that originates on the continents or islands from erosion, volcanic activity, or blown dust

How is lithogenous sediment transported?

- water

- wind

- ice

- gravity

Water movement of Lithogenous Sediment

streamflow carries 20 billion tons of sediment to continental margins 40% from Asia

Wind movement of Lithogenous Sediment

travels far from the continental margin

Glacial movement of Lithogenous Sediment

ice-rafted debris

Gravity movement of Lithogenous Sediment

landslides, turbidite deposits

Where can you find lithogenous sediment?

- Bays and Lagoons

- Deltas at river mouths

- along beaches/ shorelines

- far out

- greatest amount at continental margins

Types of Lithogenous Sediment

- Neritic Sediment

- Pelagic Sediment

Neritic Sediment

on continental shelves, shallow water deposits, close to land, coarse, quick deposit

Pelagic Sediment

deep ocean basins, deep water, fine grained, slowly deposited

Examples of neritic lithogenous sediment

beach deposits, continental shelf deposits, turbidite deposits, glacial deposits

Examples of pelagic lithogenous sediment

- Volcanic ash (volcanic eruptions)

- Wind-blown dust

- Fine-grained material transported by deep ocean currents

Abyssal Clay

- 70% clay sized particles from continents

- abundant if other seds are not

- pelagic

biogenous sediment

- derived of the remains of hard parts of once living organisms

- when organism with bones, teeth, shells die it accumulates on ocean floor

Major Types of Biogenous Sediment

- macroscopic= visible by naked eye shells, bones, teeth

- microscopic (more abundant) tiny shells, biogenic ooze

What are Biogenous sediments made of

- mainly algae and protozoans

- most common chemical compounds: calcium carbonate, silica

What are siliceous oozes comprised of?

Silica (SiO2) and skeletal material of radiolarians, diatoms, and sponge spicules.

Where do siliceous oozes accumulate?

In areas of high productivity.

What must happen before water can dissolve siliceous oozes?

They must accumulate.

Diatoms

- microscopic algae

- photosynthetic only found in upper, sunlit surface waters

- free floating planktonic

Radiolarians

- single cell protozoan (animal)

- planktonic

- external food sources

tests

shells of microscopic organisms

siliceous ooze

Tests from diatoms and radiolarians generate ________.

What are calcareous oozes formed by?

organisms that contain calcium carbonate

Foraminifera

- microscopic protozoan

- mostly planktonic but can also be benthic

- rely on external food sources

What ooze does foraminifera create

calcareous

lysocline

- depth at which calcium carbonate begins to dissolve rapidly

- scarce >5000 m

calcite compensation depth

- depth calcium carbonate dissolves

- warm shallow sea saturated

- cool deep ocean unsaturated

Average lysocline

4000 m

Average calcite compensation depth

4500 m

How does calcareous ooze move below CCD?

- seafloor spreading

- other sediments (red clay, siliceous ooze) deposit on top protecting ooze from dissolving

hydrogenous sediment

derived from the dissolved materials in water precipitating

Precipitation

is the change from the dissolved to the solid state resulting from a change in conditions

types of hydrogenous sediment

manganese nodules

phosphates

carbonates

metal sulfides

evaporite salts

manganese nodules

lumps of metal oxides, layered structure w/ precip around nucleus (tooth, bone, coral), slow growth rate

phosphates

occurs in shallow water with high bio productivity, contain 30% phosphorus

- used in fertilizer

carbonates

- calcium carbonate

- creates oolites: small calcite spheres with layers like an onion formed in shallow waters

- mining for cement

metal sulfides

- found near hydrothermal venting along ocean ridges

- rich in iron, magnese, nickel, copper, etc

evaporites

minerals that precipitate when seawater evaporates

ex: white salts -> Halite and Gypsum

cosmogenous sediment

- derived from extraterrestrial sources

- space dust

- formed by impacts on earth or other planets

- small amt of sed

What does marine sediments produce

petroleum among other things

Atom

building blocks of all matter

protons

number of them distinguishes chemical elements

molecules

two or more atoms held together by shared electrons

covalent bond

strong chemical bond formed by sharing of electrons between two atoms

water as a molecule

- strong covalent bond with two Hydrogen bond and one oxygen bond

- bent shape gives unique properties

hydrogen bonding in water

- Each water molecule is attracted to another through hydrogen bonding

- H2O has small neg charge at O and pos charge at H

cohesion

molecules sticking together allows for high water surface tension

ionic bonds

electrons gained or lost produces ions

heat capacity

amt of heat energy it takes to raise temperature of 1 gram of substance by 1 degree Celsius

does water have high heat capacity

yes, it can absorb a large amount of heat before temperature significantly increases

What causes surface waters at low latitudes to warm?

High Sun angle

How deep is the warm surface mixed layer at low latitudes?

Up to 300 meters

What are some mixing mechanisms that contribute to the warm surface mixed layer?

Currents, waves, tides

thermocline

abrupt change of temperature with depth

temperatures at high latitudes

Surface and deep waters cold year-round. No thermocline

Evaporation

conversion of liquid to gas at a temperature below boiling point

marine effect

Oceans moderate temperature changes from day to night and during different seasons

continental effect

land areas have greater range of temperatures from day to night and during different seasons

salinity

- total amt of dissolved solids in water

- avg ocean salinity: 35 ppt

- chem component always in same concentrations

how to measure salinity

evaporation, salinometer, chem analysis

hypersaline

- waters that are highly or excessively saline

- areas of high evap and limited circulation

ex: Dead Sea

How does salinity affect density

higher salinity =greater density

halocline

depth where there is a rapid change in salinity

Why does ice float?

As water freezes, it expands(change in molecular packing) and its density decreases

what temperature does seawater freeze at

-1.8°C

Pynocline

an abrupt change in density with depth

where is the mixed layer

above the clines

What is the more important factor in determining sea surface density: salinity or temperature?

temperature

Where is surface temperature the highest

the equator

Where is salinity the highest?

near the equator

where is density the lowest?

the equator

Ocean pH

-Seawater is slightly alkaline with 7.8-8.1 pH

-Ocean water pH decreases with depth in cline region

Why does ocean pH decrease with depth

-initially b/c biological remineralization in tz

-buffering kind of brings it back up

Covalent vs. Hydrogen Bonds

Hydrogen bonds are much weaker than covalent bonds. Hydrogen is attraction between Hydrogen atom in one molecule to O/N atom in another while covalent is attraction between 2 atoms

What direction do subtropical gyres rotate

NH: clockwise

SH: anticlockwise

What are subtropical gyres?

Large circular moving loops of water driven by wind belts.

At what latitude is the center of each subtropical gyre located?

30 degrees North or South.

five subtropical gyres

North Atlantic, South Atlantic, Indian Ocean, North Pacific, South Pacific

what are subtropical gyres made of

equatorial currents, western boundary currents, northern or southern boundary currents, eastern boundary currents

eastern boundary current

carry cool water from high latitudes towards equator

western boundary current

carry warm water from the equator to higher latitude

subpolar gyres

Rotate opposite subtropical gyres

Smaller and fewer than subtropical gyres

equatorial countercurrent

- when water in a pile up flows back downslope under the influence of gravity

- creates a narrow eastward current between two westward flowing equatorial currents

Antarctic circumpolar current

-the only current that flows completely around the globe

-transports more water than any other current

Fridjof Nansen

Norwegian explorer interested in determining whether there was land in unexplored arctic

- consulted indigenous people before venturing on three year journey

What did Nansen learn

that arctic ice moves 20-40 degrees to the right of the wind blowing

Ekman spiral

surface winds drive surface currents, and each layer of water drags the layer below, but the Coriolis Force changes each layer's direction slightly (45 degrees) to make a spiral effect

Net Ekman Transport

90 degrees different from wind direction

What causes seasons

Earth's 23.5 degree tilt

equinoxes

sun is directly above equator

Solstice

earth's axis is tilted the furthest toward (summer) or away (winter)

What area receives the greatest amount of solar radiation

Tropics

Why does solar radiation diffuse more at high latitudes?

low angle of incidence