WACE Marine Maritime Studies ATAR flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Neritic zone

The shallow water column above the continental shelf, generally less than 200 m deep. It is nutrient-rich and supports most commercial fisheries.

Thermocline

A layer in the ocean where temperature falls rapidly with depth, separating warmer surface water from colder deep water and limiting vertical mixing.

Spring tide

A tide of maximum range occurring at new and full moon, when the gravitational pulls of the Sun and Moon align to reinforce each other.

Longshore drift

The movement of sediment along a shoreline caused by waves striking the coast at an angle, with material carried in the direction of the prevailing wave approach.

Biomagnification

The increasing concentration of a persistent substance, such as mercury or PCBs, in organisms at successively higher trophic levels of a food chain.

Maximum sustainable yield

The largest catch that can be taken from a stock year after year without reducing the population's ability to replenish itself.

Bycatch

Non-target species caught incidentally during fishing. It includes undersized fish, seabirds, turtles and marine mammals, and can be reduced by modified gear.

Eutrophication

Nutrient enrichment of coastal water that triggers algal blooms; when the algae decay, oxygen is depleted and hypoxic dead zones form.

Reserve buoyancy

The watertight volume of a hull above the waterline. It provides the reserve that keeps a vessel afloat when weight is added or the hull is damaged.

Metacentric height

The distance GM between the centre of gravity and the metacentre. A small positive value gives a stiff, rapid roll; a large value gives a tender, slow roll.

Righting lever GZ

The horizontal distance between the centre of gravity and the vertical line through the centre of buoyancy when a vessel is heeled, producing the righting moment.

Angle of loll

An unstable condition of zero or negative metacentric height in which a vessel lists to either side. It is corrected by lowering the centre of gravity.

Block coefficient

The ratio of a vessel's underwater volume to the volume of a rectangular block with the same length, breadth and draught; it indicates hull fullness.

Four-stroke cycle

A diesel engine cycle completed in four piston strokes: induction, compression, power and exhaust, requiring two crankshaft revolutions per cycle.

Propeller slip

The difference between the theoretical advance of a propeller (pitch times revolutions) and the actual distance travelled through the water, expressed as a percentage.

Cavitation

Formation and collapse of vapour bubbles on a propeller blade where local pressure drops below vapour pressure, causing noise, vibration and surface erosion.

Controllable-pitch propeller

A propeller whose blade angle can be altered while running, allowing thrust to be reversed or optimised without stopping or reversing the engine.

Series versus parallel batteries

Cells connected in series add their voltages while capacity stays the same; cells in parallel add capacity while voltage stays the same.

Variation and deviation

Variation is the angle between true and magnetic north at a location; deviation is the error caused by the vessel's own magnetic field affecting the compass.

Dead reckoning

A position calculated from the last known fix by applying course steered and speed through the water over the elapsed time, without correcting for tide or leeway.

Estimated position

A dead reckoning position corrected for tidal set and drift and for leeway, giving a more realistic position than course and speed alone.

Beaufort scale

A scale from 0 to 12 describing wind strength by observed sea conditions; force 7 is a near gale of 28 to 33 knots.

Crossing rule COLREGs

When two power-driven vessels cross, the vessel with the other on her starboard side is the give-way vessel and must keep clear.

MAYDAY

The international radiotelephony distress signal, spoken three times on VHF channel 16, indicating grave and imminent danger requiring immediate assistance.

EPIRB

An emergency position-indicating radio beacon transmitting on 406 MHz to alert rescue authorities via satellite, with a 121.5 MHz homing signal for local search.

Fire triangle

The three elements needed for combustion: fuel, oxygen and heat. Removing any one element extinguishes the fire.

MARPOL Annex V

The annex of the marine pollution convention regulating garbage disposal from ships, prohibiting most plastics overboard and restricting other waste by distance from land.

Port state control

Inspection of foreign-flagged vessels in port by the coastal authority to verify compliance with international safety, pollution and crewing conventions.

Bareboat charter

A charter in which the charterer hires the vessel without crew, taking responsibility for manning, operating and insuring her for the charter period.

Time charter

A charter agreement in which the charterer hires a fully crewed vessel for a fixed period, paying hire and usually bearing fuel and port costs.

General average

A maritime principle in which losses deliberately incurred to save a ship and cargo from a common peril are shared proportionally among all parties.

Flag state

The country whose flag a vessel flies. It is responsible for registering the ship and enforcing international safety and pollution standards on board.

Blue economy

The sustainable use of ocean resources for economic growth, livelihoods and jobs while preserving the health of marine ecosystems.