world oceans lab midterm review

Oceanic Crust

• 5-7 kilometers in thickness

• 3.0 g/cm³ in density

• composed of basalt and gabbro

• DENSER than continental

Continental Crust

• 40-70 kilometers in thickness

• 2.7 g/cm³ in density

• composed of granite

• LESS DENSE than oceanic

Convergent

When two plates move towards each other and collide

1) continental and continental form mountains

2) continental and oceanic form a volcanic ark (oceanic subducts under continental and magma forms volcanic ark)

3) oceanic oceanic form an island ark (older less dense subducts and island ark is formed)

Divergent

When two plates move away from each other

• this can form mid atlantic ridges and volcanoes

Transform

When two plates slide past each other

• this creates a transform fault line (ex the san andreas fault)

Calcareous Ooze

composed of calcium carbonate

• foraminifera, coccoliths, and pteropods

• ABOVE CCD

Silicious Ooze

composed of silica

• radiolarians, diatoms, and sponge spicules

• BELOW CCD

What is the CCD

Calcium Carbonate Depth, this is where calcium carbonate dissolves because of high pressures and cold temperatures

the CCD for the Atlantic is 4500 meters and the Pacific is 3500 meters

Lithogenic sediments

• derived from land masses

• can be either terrigenus or volcanic

  • terrigenus is broken pieces of rocks

  • volcanic is cooled magma

Biogenic sediments

sediments composed of bits or plant and animal skeletons (salacious and calcareous oozes)

Hydrogenic sediments

Sediments derived through precipitation and evaporation of seawater leaving the minerals and sediments

Volcanic ark

A volcanic arc is a chain of volcanoes that forms above a subducting oceanic tectonic plate, typically arranged in an arc shape, parallel to an oceanic trench, where one plate is sliding underneath another, resulting in the melting of rock and magma rising to the surface to create volcanoes along the arc

Island ark

An island arc is a curved chain of volcanic islands that form at the edge of an ocean basin. They are often associated with intense seismic activity

Hot spot

an area of volcanic activity, especially where this is isolated usually not on a plate boundary

Mid-ocean ridge

A mid-ocean ridge is a long, continuous mountain range on the ocean floor formed where two tectonic plates are pulling apart, creating new oceanic crust along a divergent plate boundary

Trench

a long, narrow depression on the ocean floor, typically formed at the boundary where one tectonic plate is pushed beneath another (subduction zone), marking the deepest parts of the ocean

Chemical and physical properties of water

• normal seawater varies in salinity from 32 to 37 ppt with an average of 35 ppt

• freshwater is measured in millions and lower than saltwater

• the pH of the ocean averages 8.1

how oxygen is produced in the ocean

• photosynthesis- plants take in carbon and release oxygen

• aeration- the ocean absorbs oxygen and other gases from the atmosphere

Secchi disk

A Secchi disk measures visibility of water- you put the disk into water and mark when it isn’t visible anymore

Optimum conditions for coral reefs

• warm shallow waters with abundant sunlight

• 20-30 degrees Celsius/ 68-86 Fahrenheit

• salinity between 32-40 ppt

TDS vs salinity

TDS- total dissolved solids into water (includes salt EVERYTHING)

salinity- purely salt dissolved into water

visibility

measure of the depth you can see into the water

density

mass per unit volume, density increases as water temp decreases or as salinity increases

pH

how acidic or basic a substance is (1-7 ACIDIC, above 7 BASIC)

Relationship between density, temperature, and salinity

• as temp increases, density decreases

• as density increases, salinity increases

• evaporation increases salinity and density, while the addition of freshwater decreases salinity and density

how to identify a rip current

• can occur at any beach with breaking waves

• breaks in incoming waves

• channel of choppy, murky water

• difference of watercolor

• line of debris or foam moving seaward

Diurnal

one high tide and one low tide per day

Semi-diurnal

two high tides and two low tides per day

Mixed semi-diurnal

semi-diurnal but different wave amplitudes

Upwelling

wind pushes warm shallow water away while colder water from the bottom rises up and takes its place

Wave crest

top of a wave

Wave trough

bottom of a wave

Wavelength

distance of one crest to the next (meters)

Wave height

vertical distance from trough to crest (meters)

Wave period

length of time required for a wavelength to pass a given point (second) (period= 1/frequency)

Frequency

number of waves that pass a given point in a fixed amount of time, measured in Hertz (1 hz = 1 cycle per second) (frequency= 1/period)

Celerity

wavelength divided by wave period measured in units of velocity (meters/second)

Shallow water waves

• depth of half a wavelength or less

• orbits of water become more flattened with increasing depth

Deep water waves

• depth of water is greater than half the wavelength

• movement is circular and the diameter of the circle decreases with increasing depth

Constructive waves

• summer months

• less storms

• less energetic

• causes gentle slope

• fine sediments

Destructive waves

• winter months

• more storms

• more energetic

• steep slope

• coarser sediments

Spilling breaker

• gradually peaks

• slow energy

• low angles of slope

Plunging breaker

• suddenly break

• quickly release energy

• moderate slope

Surging breaker

• builds up like a plunging but the base of the wave travels faster than the top so its not a rip curled

• happens a steep angles

Bar

Raised area of sediment on the ocean floor with waves

Berm

a gentle slope with fine sediments and a wide mound