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66 Cards in this Set
- Front
- Back
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when did oceanographers realize that there was an immense undersea volcanic mountain chain that ran through all of the oceans?
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in the 1950s
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When was the first comprehensive and generally accurate bathymetric map produced?
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1959
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what is teh average ocean depth?
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3.8 km
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what is the pressure (in atmospheres) at a depth of X meters?
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X/10 + 1 atmospheres (1 atm of air pressure + 1 atm per every 10 meters)
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What are some of the difficulties faced by oceanographers in studying the ocean?
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- they can't breate in water
- water absorbs light and other forms of EM radiation such as radio and radar waves - ocean is very deep - presure is high - seawater is corrosive - equipment can be fouled, samples contaminated - seawater is slightly conductive, causing short circuits in electronic equipment - sea surface is dynamic |
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about how many deep ocean soundings had been made by 1910?
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6000
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when making a sounding, what is the relationship between the amount of wire let out and the actual ocean depth?
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actual ocean depth is always much less than the amount of wire let out because of currents in deep waters and on the ocean surface
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why must wires used for depth soundings be made several times stronger?
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they must pull their own weight and the weight of the instruments attached to them
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how do oceanographers solve the problem of wires wrapping around the ship?
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a Bow Thruster Propeller is attached perpendicular to the direction of the boat to "unravel" the wire
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who made the first successful echo sounding? when?
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German scientist Alexander Behm, in 1920 (in the North Sea)
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who invented the echo sounder and why? what year?
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Reginald Fesser in 1912, in order to locate icebergs (becasue of the whole Titanic thing)
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what is the problem with the PDR (Precision Depth Recorder)?
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it often overlooks undersea hills and mountains?
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who produced the first sea floor map in 1959?
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Bruce Heezen and Marie Tharp
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What is the difference between the Multibeam Sonar and Sidescan Sonar?
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-Multibeam Sonar= US; 16 beams are projected in a fan like fashion and the intensity of the returning beams informs scientists of sea floor relief
-SideScan Sonar- British; 2 wide sound beams are projected at an angle from a "fish" towed under the boat; intensity of returning beam informs scientists of sea floor relief |
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what does SONAR stand for?
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SOund NAvigation and Ranging
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what was the SEASAT?
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the first sattelite devoted entirely to oceanographic studies; 1978
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what was the difference between the GEOSAT and SEASAT?
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GEOSAT, the successor to SEASAT, used a more accurate Radar Altimeter, to determine the height of the sea surface with a precision of 3 to 6 cm
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how were early sediment samples collected?
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they adhered to a lump of tallow at the end of a sounding line
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what is Sir John Ross famous for?
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while exploring Baffin Bay in search for the NW Passage in 1820, he used the Deep Sea Clam (an early version of the grab sampler) to collect sea floor sediment
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what is one problem with the grab sampler?
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it hinges like a clam shell, so the sediment it retrieves is often mixed
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why is the box core better than the grab sampler?
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it minimizes distrubance because a thin blade slides under the box to prevent sediment from falling out, which also prevents mixing of sediment layers
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how does a corer collect sediment?
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a tube is forced vertically down by an attached weight with great force; sediment goes inside the tube and is held inside by a core catcher
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what's the difference between a gravity corer and a piston corer?
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gravity corer- weight lowers it into sediment and falls freely; sediment is driven into the core as it hits the ground with great force
- pisto corer- tube is attached to a release mechanism at the end of a cable; it gets more sediment layers and minimized vertical distortion of core's sediment layers |
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how big are sediment samples taken by corers?
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10-30 m
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the Deep Sea Drilling Project, in 1968, used this ship to obtain more than 1000 cores from throughout the world ocean
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Glomar Challenger
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the Glomar Challenger was replaced by this ship in 1990
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Joides Resolution
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_______ succeeded the DSDP in 1983
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Ocean Drilling Project (ODP)
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what countries became members of the ODP?
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US, Germany, UK, France, Japan, Australia, and and one point, the USSR.
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how old is the oldest sediment sample? what ship retrieved it and how deep was the sample?
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170 million years old; Joides Resolution; 5700 m
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how does seismic profiling "work"?
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a sound wave or shockwave is reflected and refracted partially at each sediment layer; different sediment layer reflect different echoes; returning echoes are montitored with a string of HYDROPHONES towed behind a research vessel
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what else, besides seismic profiling, is used to study ocean sediment layers?
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magnetic field and gravity changes
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what are dredges?
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steel nets that obtain rocks and Mg and P nodules; dredges must be extremely strong
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what is the diameter and length of the rope that tows a dredge?
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1 cm; 10 km
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what are sampling bottles used for?
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to collect water
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how thin is the surface microlayer?
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100 micrometers
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why is the surface microlayer significant?
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it often contaminates sampling bottles because the layer contains large quantities of various dissolved chemicals
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what's so special about the GoFlo sampling bottle?
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it's closed when it is released from the boat, but after it reaches a depth of a few meters, the change in pressure causes it to open and collect seawater from a certain depth; this prevents contamination by the surface microlayer
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why are sampling bottles configured so that water continuously flows in and out of it?
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to prevent crushing by the immense pressure
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what is used to determine the temperature of a sampling bottle at the time the sample was collected?
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a reversing thermometer
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why must a reversing thermometer be used?
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because the high pressures causes the column of mercury to rise higher than it normally would
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what do CTD and STD stand for?
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CTD = conductivity, temperature, depth
STD = salinity, temperature, depth |
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describe a Rosette Sampler
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12 sample bottles are put around a CTD sensor package, which measured salinity and temperature continouously as a function of depth
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true or false: temperature, salinity, and depth sensors are more effective and reliable than pH and turbidity sensors
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true
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what are the 3 types of current measurement devices?
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1. passive devices (float)
2. current meters (anchored to ground) 3. remote sensing systems (have remote sensing systems....duh) |
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give examples of passive sampling devices
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-Drifters: they float on the surface of the water
-Drift Cards- wash up on the shore and people that find them mail them to oceanographers; useful for determining paths of currents -Swallow floats: neutrally buoyant- float in the middle of 2 different seawater layers of differing density |
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briefly describe current meters
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they're anchored to the ground;
some have an impeller that faces the current; others have a rotor that faces vertically; others rely on current meter to tilt the meter body - the meter is oriented to align itself with the current direction with the use of one or more vanes or fins |
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how is direction determined with current meters?
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with the use of a magnetic needle inside the meter body
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what does the CAT in CAT scan stand for?
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computerized axial tomography
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breifly describe acoustic current meters
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-they're expensive
-they send echoes and current speed and direction are calculated by using the Doppler Shift of the sound frequency of the returning echoes |
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what is an advantage of the acoustic current meter?
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it measures current speed and direction at all depths above or below the meter
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how are the smallest pelagic organisms (bacteria, phytoplankton) collected?
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with the use of sampling bottles or plankton nets
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how are medium sized to large sized marine organisms captured?
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with a large net (often a km long)
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how are very fragile organisms collected?
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in a bottle or jar
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describe the "slurp gun"
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it's a syringe like device used to catch fragile or elusive smallfish and other organisms
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what is an advantage of computer tomography?
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it can measure current speed in large areas hundreds of square kilometers
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what is an advantage of the JASON-MEDEA system?
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JASON can return samples to MEDEA instead of going all they way up to the research vessel
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what ROV(s) first explored the Titanic wreck?
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ARGO and Jason, Jr.
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how long can the JASON-MEDEA system work continuously?
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about one week
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with what precision can the JASON-MEDEA system reolocate a particular area on the sea floor?
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a few meters
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how long would it take for a sattelite to survey the entire world ocean?
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a few days
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what is a disadvantage of using sattelites to study the oceans?
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since water is a good absorber of EM radiation, sattelites can only study the upper portion of the oceans
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how deep can scuba divers descend (safely)?
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90 m
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in order to avoid the bends, how long must scientists spend in a decompression chamber after spending several days in an underwater habitat?
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several days
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what is nitrogen narcosis?
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a life threatening condition when high pressure air causes high concentrations of nitrogen to build up in the bloodstream, which then produce symptoms similar to those of alcohol intoxication; if the excess nitrogen cannot escape the blood, and forms damaging gas bubbles in the body
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describe the bends
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a life threatening medical problem caused by a diver breathing high pressure air at a depth for too long and returning to the surface too quickly
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when was the mariana trench visited? by what bathyscape?
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in 1960; by the Trieste
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