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133 Cards in this Set
- Front
- Back
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What was known about the oceans by the middle of the 19th Century?
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They cover 2/3 of the planet's surface and, except for coastal areas, are very deep.
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When was the first bathymetric map made by who?
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1959, by Bruce Heezen and Marie Tharp
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What are the six problems facing ocean researchers?
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We can't breathe in water; water is opaque to light and other EM radiation; the oceans are deep; pressure is high at the bottom; seawater corrodes, and the sea surface is dynamic.
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How did 1920s and later oceanographers "see" the ocean floor?
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using sound waves
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What can satellites measure directly for oceanography?
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They can map the ocean surface very accurately, but can't reach the ocean floor.
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What are the average and greatest depths of the oceans?
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3.8km and 11.04 km respectively
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What are the average and greatest heights on land?
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840 m and 8848 m respectively
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What are two effects of the inaccessability of the oceans?
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Ocean bottom water and sediment samples are very time-consuming and expensive.
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What is the relationship of pressure to oecan depth?
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increase pressure by 1 atmosphere for every 10 meters of depth
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Why is ocean pressure a problem?
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Deep-diving submersibles and submarines must be built of durable materials that can withstand the pressurizing and depressurizing effects of descent and ascent repeatedly.
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What happens to electrical equipment in seawater?
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It short circuits, because seawater conducts electricity.
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What problems does corrosion pose for ocean researchers?
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Wires, cables, sampling devices, and instrument housings must be protected, and trace metal measurements are often contaminated by corrosion of the sampling devices.
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What is generally used now to make wires and hold up instruments?
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marine-grade steel, coated in grease or plastic
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How can marine organisms pose problems for marine researchers?
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They can foul instruments that are left in the ocean for long periods of time, like barnacles, which grab onto any solid material.
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What problems arise from the dynamic nature of the ocean?
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This causes seasickness, makes it difficult to apply equipment accurately, breaks many scientific instruments, and can sweep away valuable instruments during bad weather.
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What are two of the technical difficulties faced by ocean researchers?
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Broken equipment must be repaired on the spot, and research to particular locations is relatively rare.
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What is bathymetry?
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measuring the depth of water over the ocean floor
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What was the first bathymetric measuring technique?
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soundings: drop a line with a weight at the bottom until it hits the floor, then measure the length of the line
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What is a fathom and where did it come from?
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Originally, it was 5.5 feet, the distance between the hands of a man with outstretched arms. Later, it was relabeled as 6 feet.
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How were bottom samples originally taken?
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The sounding weight was made of tallow, which would adhere to bottom sediments.
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How were bottom sediments originally classified?
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as sand, silt, or mud, with the mud color usually noted
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What did the USS Tuscarora change in 1885?
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soundings, by using a drum and a winch to lower and raise the sounding line rather than pulling it
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What is wrong with deep soundings?
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For deep depths, the wire starts to weigh a lot, and its weight can continue to pull the drum.
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What is a problem soundings have in inclement weather?
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The ship rocks, which makes the tension in the string flucuate considerably.
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How do currents mess up soundings?
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Surface currents can push the ship to one direction of the sounding weight, while deep currents can push the weight in another direction.
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How can the ship interfere with sounding measurements and how is the fixed?
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The line can get pushed under the vessel, which can damage the hull or break the wire. To fix this, the ship turns around to the other side, leaving the wire in its place.
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Why was sonar developed by who when?
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Reginald Fessender invented sonar to detect icebergs in response to the Titanic sinking in 1912.
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Where and when did who succeed in measuring depth with echo sounders?
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1920 Alexander Behm made echo sounder depth recordings in the North Sea.
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What is the biggest advantage echo sounders give?
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rapid measurements of ocean depth under a moving ship
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What are depth-measuring echo sounders called today?
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precision depth recorders, or PDRs
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What two techniques were developed in the 1960s to cover a large portion of ocean floor with sonar?
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Americans developed the multibeam sonar, which used 16 narrow sound beams in a fan-like arrangement, while the British made sidescan sonar, which sent two broad beams of sonar from a "fish" towed behind the research vessel.
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Why did the US DOD try to classify ocean floor maps made by US researchers?
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They could be used to find places to hide submarines.
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How do satellites measure seafloor depth?
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Using a radar altimeter, they measure very accurately the sea surface, which bulges when rock is underneath, because undersea mountains will attract water gravitationally.
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What were the two major satellites used to map the ocean surface?
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SEASAT and GEOSAT, in that order
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What are the two types of sediment oceanographers try to obtain?
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an undisturbed core from the surface to as deep as necessary for historical purposes, and samples over a large area to get the organisms in the upper layer of sediment
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Who first invented a device to take large samples of the ocean floor when?
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Sir John Ross in 1820 had his blacksmith make a "deep-sea clam", similar to a grab sampler
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What are grab samplers?
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two hinged metal container halves which close when the "clamshell" hits bottom
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What are grab samplers used to obtain?
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surface sediments
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What are box cores?
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heavy rectangular boxes with open bottoms that are lowered into sediment, sealed on the bottom, and raised
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What is the main plus and the main minus of using box cores to get sediments?
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They disturb the sediment very little but are very heavy.
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What features do all corers exhibit?
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a tube that is forced down into the sediment and is then pulled out, with a core catcher keeping the sediment from falling out
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What are the two main types of corers?
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gravity corers and piston corers
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How does a gravity corer work?
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The tube is forced into the sediment by gravity, being allowed to fall from a height.
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How does a piston corer work?
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When the corer hits the ground, a piston pulls up on the water in the corer, which sucks the sediment in, or at least reduces the pressure on it.
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What is a feature of some gravity corers and all piston corers?
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a release mechanism that deploys the corer at a specified height
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What is required to take longer sediment cores?
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heavier corers
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What sediment is difficult to core?
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very sandy sediment and other special situations
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How and when did oceanographers penetrate deeper than corers take them?
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starting in 1968, by drilling holes in the ocean floor and taking drill core samples up to thousands of meters deep
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What are the names of deep ocean floor drilling projects?
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Glomar Challenger, which was later replaced by Joides Resolution
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Besides the sediment samples, what did core drilling of the ocean floor do for oceanography?
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It confirmed seafloor spreading and continental drift theories.
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What is seismic profiling?
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using sonar to detect changes in rock or sediment density of the seafloor
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What are three ways sediment layers can be detected and analyzed?
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from drill cores, using sonar (seismic profiling), and by measuring slight changes in the gravitational field
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What are dredges used to collect?
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manganese and phosphorite nodules and other rocky sediments, often attached to solid lava flows
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What are the requirements a dredge must have?
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Its tow cable must be very strong to break rocks loose, and the ship must be powerful to hold the drum and wedge on and carry the long, heavy cable.
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What does a dredge consist of?
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a strong metal frame with a net or mesh behind to catch the rocks
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Why are samples of ocean water taken?
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because very few chemical studies can be conducted in the ocean itself
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Which samples are not collected in bottles?
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shallow water samples, which are vacuumed through a pump
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How are samples taken at different depths nearly simultaneously?
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Bottles are attached at each depth to a line, then a messenger is sent to the first bottle, which closes and releases a second messenger, etc.
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What kinds of bottles are used to collect seawater?
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For a long time, Nansen bottles were used, but newer technology is taking their place.
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What are three sources of contamination of water samples?
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the sampling device itself, contaminants where the sample is stored in the ship and lab, and the surface microlayer
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What is the surface microlayer?
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the .1 mm-thick layer on top of the world ocean containing higher concentrations of many chemicals as well as oils and other discharges
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How does the surface microlayer contaminate Nansen bottles?
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It deposits a film on the inside of a sampling bottle that is open as it is lowered into the ocean.
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What design keeps the surface microlayer from contaminating the sampling bottle?
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The GoFlo sampling bottle is closed but opens under a pressure of just a few meters.
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How are reversing thermometers used to measure temperature at depth?
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Reversing thermometers trap the mercury when they flip over, measuring the temperature at that depth.
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How are reversing thermometers used to measure depth?
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One protected and one unprotected (at pressure) thermometer are lowered and their readings give the pressure, which is used to calculate depth.
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What does CTD stand for?
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conductivity, temperature, and depth
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What were sampling bottles replaced by when?
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1970s by packages of instruments that measure continously as they are lowered and raised
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What advantages and disadvantages do CTDs have over sampling bottles?
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They measure continuously and provide instant results, but require electric power to be lowered to that depth and stonger cables without measuring everything that can be measured from water samples.
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What do rosette samplers do?
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both sample water at realtime-selected depths and contain CTDs which measure those properties
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What sensors could possibly be appended to CTDs?
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pH, dissolved oxygen and turbidity
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What are two indirect methods of measuring currents?
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using salinity and temperature distributions or chemical or radioactive tracers
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What are three direct methods of measuring currents?
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passive devices that go with the flow and record locations, anchored current meters, and remote sensing ship-based methods
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What are three passive current-measuring devices?
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drifters, drogues and floats
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What are drifters?
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items that are released into the ocean to be discovered and reported later by someone
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How are drift cards used to measure currents?
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Many are released in one spot; they eventually come ashore, where someone finds them and reports where.
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How are drift cards useful?
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to figure out where wastes or oil will end up if it is spilled
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How do drogues measure currents?
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A parachute is attached at a specific depth, and it "sails" in the current, dragging a styrofoam float with a radar reflector along with the current.
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How are floats used to measure currents?
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Set at a predetermined density, or depth, they periodically produce short "pings" which are received at multiple locations and triangulated.
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What is another name for floats?
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Swallow floats, after their inventor
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What are the three types of fixed current meters?
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those with an impeller that rotates, those with a rotor with a vertical axis, and those that are tilted by a current
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What do all three fixed current meters have in common?
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a vane that orients them in the direction of the current
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How are fixed current meters positioned properly?
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They are distributed regularly along a line from a mooring.
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How are fixed current meter moorings released and why?
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Weights at the bottom are cut free by an acoustic signal, so the meters are not tampered with or stolen by other people.
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What is a very inexpensive way to measure coastal currents?
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Attach a bottle filled with heated wax to two rocks via two LifeSaver candies, which eventually dissolve, and stick a compass needle in it to measure direction. The wax solidifies at an angle indicative of the current speed.
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How is sonar and remote sensing used to detect currents?
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narrow, focused sound beams of a particular frequency are sent out and the echoes' frequencies are measured to get current velocity due to the Doppler shift
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What are the advantages and disadvantages of using remote sensing to detect currents?
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It can be done where heavy traffic prohibits stationary objects or where current speeds are very high, but needs lots of data and computing power to find current velocities.
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What is acoustic tomography?
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Signals are sent between several stationary transmitters, and the speeds are measured, giving a detailed layout of temperature and salinity, which can be used to measure currents.
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Where are organisms found in and around the ocean?
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throughout the water and in the upper part of the soil
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What are five problems associated with capturing animals from the ocean?
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You have to use a lot of water; species range incredibly in size; many swim away; many are delicate and are damaged by sampling devices; many live in different conditions than those we bring them to.
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What is the primary type of sampling device for pelagic species?
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nets
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How do biologists collect species from a specific depth?
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A weighted net is dragged behind a ship.
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What is needed to determine population density from netted organisms?
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the amount of water filtered
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What are two ways to measure the amount of water filtered through a net?
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flow meters and calculations based on cross-sectional area over a distance
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How are small pelagic organisms sampled?
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by collecting samples of water
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How are large pelagic organisms sampled?
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fishing lines and lures
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How are benthic fish and invertebrates sampled?
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with trawl nets towed across soft sediment or dredges towed across rocks
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How are elusive organisms sampled?
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baited traps, lures, light for deep water, such as the lobster pot
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What are examples of fragile organisms that can be damaged by catching them?
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hydrothermal vent communities and plankton near the surface
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How can fragile organisms be collected?
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Divers or ROVs can capture them carefully, often using a slurp gun, which vacuum them up.
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In what sorts of sampling are people necessary?
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jumbled rock formations, coral reefs, and those that must be observed in their natural habitat
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Why can scuba divers only sample in the upper 90 meters of the ocean?
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They have trouble with the bends and nitrogen narcosis.
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What is nitrogen narcosis?
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when the high pressure forces nitrogen gas into the blood stream, making a scuba diver behave drunk-like
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How are underwater habitats used to study the marine environment?
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Scientists stay in them and go out for short periods of time on scuba excursions.
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What is the main advantage of underwater habitats?
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They allow close biological and behavioral study of organisms at depth.
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What is the bends?
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a problem associated with divers breathing the high pressure air at depth and then returning too quickly to the surface
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What are the main disadvantages of underwater habitats?
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They are very expensive, immobile, don't affect the limitations of scuba, and require long rehabilitation times after divers use them.
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What can manned submersibles do?
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observe and photograph organisms and seafloor, and collect organisms, rocks, sediment, or water samples.
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How many scientists can go in a manned submersible?
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1 to 2 or 3
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When did who build and use the first submarine? What was it made out of?
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1620 Dutchman Cornelius Drebbel made a waterproof sub out of the outer skin of leather.
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What were early submersibles called?
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bathyscaphes or bathyspheres
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When did exploration subs reach their peak? With what?
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1960, with the bathyscaphe Trieste, which visited the Mariana Trench
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What do recent sub efforts deal with?
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locating precise locations on the seafloor, sample collection, and seafloor mobility
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What is some of the equipment that submersibles carry?
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sample-collecting devices, video cameras, measuring instruments, and powerful lights
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Where are submersibles primarily used?
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around underwater volcanic features and hydrothermal vents
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What are the main disadvantages of submersibles?
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They need a large vessel with a large crew to deploy them; they are very small and cramped; they have to carry everything with them, so they can't last long or cover a large area.
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What are the essential features of an ROV?
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a camera, a sled, a motor and propellor, and steering devices
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What does ROV stand for?
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remotely operated vehicle
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What advantages does an ROV have over a submersible?
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It is less expensive, can last longer, can be deployed from smaller ships, and don't need life-saving equipment.
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Why will ROVs replace submersibles someday?
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The same appendages can be added to ROVs that are on submersibles, but the controllers can operate in a comfortable environment, with perhaps a better view.
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Which ROVs explored the Titanic wreck?
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The ARGO found the wreck and Jason, Jr. worked off the sub Alvin.
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What does the Jason-Media system consist of?
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Media is attached to the ship and surveys a large area while Jason is attached to Media and looks closer and collects samples.
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What does AUV stand for?
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autonomous underwater vehicle
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What could replace ROVs?
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AUVs
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What is the difference between an AUV and an ROV?
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ROVs have a tether and can communicate directly with the controller, while AUVs are pre-programmed and operate relatively isolated from their controller.
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How long does a satellite take to survey the entire earth?
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a few days
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What are synoptic observations?
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comprehensive surveys of large areas of the ocean
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What do synoptic observations allow?
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observations of temporal variations in ocean phenomena
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What instruments do satellites use?
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radar, lasers, color-sensing scanners and infrared-sensing scanners
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What are satellites limited by?
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They can only see the first few meters of the ocean because the ocean is opaque to light.
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What did GPS and other satellite systems do for oceanography?
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They let ships determine their locations very accurately.
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How accurate can GPS be?
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within a few meters
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How are satellite observations used routinely?
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Fishers use them to find the best fishing grounds and ship captains avoid hurricanes and storms.
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What can satellites be used to detect?
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temperature, phytoplankton concentrations, turbidity concentrations, surface currents, and waves
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