Oceanography Midterm #1 – Flashcards
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What is special about the Sargasso Sea?
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It is defined by the surrounding ocean currents
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List Four Reasons to Care about the Ocean
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Lots of life (50% species), produces 70% of O2, 71% of Earth's surface, major source (20% animal protein)
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Compare Ocean depths to land heights
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ocean is 4.5 times greater than average land elevation
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what percent of Earth is covered with water?
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97%
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What percent of Earth's water is found in the ocean
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71%
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Compare and contrast the following (hypothesis, theory, law, fact)
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Hypothesis: Tentative explanations proposed Theory: Patterns emerge. If one or more of the relationships hold the hypothesis becomes a theory Law: Theories that evolve into larger constructs Facts: Law and theory can be statements of fact
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The ocean compromises what percent of Earth's mass?
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0.02%
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Largest animal to ever inhibit Earth. What does it eat?
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Blue Whale. Eats up to 40 million krill a day
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Why do waves break as they come ashore?
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Water is slowed by contact with the sea bed while the top of the wave is still moving fast so it rolls over and breaks
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Why is there so much life around volcanic islands (seamounts)?
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There's lots of nutrients because the deep ocean currents collide with the islands flanks
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What do tuna eat and what eats them?
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Tuna eat plankton feeders and sharks eat tuna
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Why do hammerhead sharks come to seamounts?
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The locals of the seamounts provide a cleaning service
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what do sardines eat and what four organisms eat them?
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Sardines eat plankton and cape gullets, sharks (bronze whaler), dolphins, and whales eat them
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Where do we find some of the roughest conditions? What does this do to the ocean productivity?
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Roughest conditions found near (south Atlantic) poles. it enriches the surface waters (food in abundance)
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Basis of all life in the ocean?
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fighter plankton
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largest migration of life on the planet. explain.
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Disappearance of the sun triggers 1,000 million tons of sea creatures searching for food near the surface (graze on fighter plankton)
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Why do sea turtles lay their eggs on the same day?
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so predators on the beach are overwhelmed so many babies get to the water
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why do herring go into shallow water?
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to breed
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why do grey whales migrate such great distances?
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seeking the krill that came to feed off the herring eggs
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how do killer whales kill a grey whale calf?
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they force themselves between mother and calf then leap onto it and push it under (drown it) and kill it
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what is special about the North Star (Polaris) and why was it so important in early navigation?
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It doesn't move so you can refer to it for navigation
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Where did the Cook voyages go and what were their contributions?
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Went to South Pacific. They found data on ocean depths, wind directions, water temperatures, and surface currents
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What was the echo sounder and why was this important to oceanography?
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It allowed measurements of seafloor bathymetry
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Satellites are being used more and more to sturdy the oceans- why are they so valuable?
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They gather large scale data over short time periods
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What prompted colonization of Polynesia and Viking exploration
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economic reasons
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why did the Chinese set out in the 1400's to launch "the greatest fleet the world had ever known"?
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To explore the other side of the world and convince nations China was the only civilized state
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Why is meant by "reverse tribute"?
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Giving things to people to show their wealth
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Who discovered North America?
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Vikings
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What research question was the focus of the Glomar Challenge?
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To test a controversial hypothesis about the history of the ocean floor
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When did oceanographic institutions get established and why?
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they evolved to ensure continuity of effort when demands became greater than any single voyages capability
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Describe the initial surface of the Earth
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Sandy with lots of craters from collision
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How and when did the moon form?
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3.9 billion years ago. Molten debris coalesced together after collision with something the size of Mars
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"habital" zone
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right distance from the sun so the oceans don't boil away/ freeze
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where did the water come from the eventually filled the oceans?
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Commets showered earth with water
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What is a thermophile?
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Organisms that can live in extreme environments
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Whats the oxygen revolution? what caused it?
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Photosynthetic organisms producing enough oxygen to oxidize minerals dissolved in ocean and surface sediments
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what's the magnetic field do and how has it influenced how Earth developed?
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Magnetic field deflects solar wind and preserves our air
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how do we think the planets formed and why do we have rocky and gases planets?
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Planets formed from space debris gravitating and being held together. We have rocky and gaseous planets because of their distance from the sun and solar winds
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Three sources of hear that caused early earth to be molten?
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Frictional heating, impacts, radioactive decay
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How does the composition of the crust differ from the whole-earth composition?
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The crust composition has light elements up and heavy elements down
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Compare and contrast the lithosphere and asthenosphere
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Lithosphere: cool, outer layer, 70-200km, composed of continental/oceanic crusts and uppermost portion of mantle Asthenosphere: hot, partially melted, slowly flowing layer of upper mantle, 350-650km
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Three types of plate boundaries and what occurs at each
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Divergent: spreading centers, new crust Convergent: sudbuction, crust destroyed Fault: sliding, lithosphere breaks
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How old are the oldest ocean rocks- why so young?
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Less than 200 million years old because sediments are conducted at a plates leading edge
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Greatest objections to Wegner's hypothesis?
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That he only selected data supporting his hypothesis, ignoring contrary evidence
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Why is the Earth's interior still hot?
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Radioactive elements within Earth's core and mantle continue to decay and produce heat
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What is a volcanic island arc? Where do they form?
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Curving chains of volcanic islands/ seamounts that occurs parallel to concave edges of trenches
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Would the most violent earthquakes be associated with spreading centers or subduction zones? why?
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Subduction zones because there was no evidence of new crust spreading centers must be balanced by destruction the crust plunges into the mantle(subduction zones are deeper and more violent)
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What's a hot spot and how can they be used to determine plate motion and rate?
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Plumes of magma rising from stationary sources of heat in the mantle
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Why are tectonic terranes and how do they form?
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Isolated part of seafloor, island arc, plateau, continental crust, or sediment brought by seafloor spreading to a position adjacent to a larger continental mass
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What does magnetic field do for us?
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It's a force field that protects us from space weather and radiation
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how can ancient pottery be used to help us understand the magnetic field?
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Pottery records the Earth's magnetic field when it goes into the film. We know the rate of change in the magnetic field has been up and down but the last 300 years there has been a rapid fall
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What would happen if the liquid core stopped moved?
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the dynamo would shut down
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How fast is Earth's core cooling?
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100 degrees per billion years
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How often have magnetic field reversals take place?
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Once every 200,000 years
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What has happened in the South Atlantic?
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Magnetic anomalies have begun under the ocean (reversing direction and cancelling out the Earth's magnetic field)
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Where do most earthquakes and volcanoes occur?
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Ring of fire and near the edges of tectonic plates
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What's the significance of magnetic strips- what do they tell us?
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They hold a record of reversals in Earth's magnetic field
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When did plate tectonics begin?
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3.2 billion years ago
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What is the difference between an ocean and a sea?
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Seas are smaller than oceans and are located where land and ocean meet
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What two instruments are needed to determine your longitude using the sun- why?
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sextant (determining latitude) and chronometer
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What were the main stimuli to European voyages of exploration during the Age of Discovery?
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Trade, military one-upmanship
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Why is the oldest ocean floor so young?
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Subduction. Oceanic crust gets colder and denser w/ age. It sinks into the upper mantle and is essentially a continuing cycle.
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How could you convince a 10 yr old that the Earth is round?
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A. You could take them to the ocean and watch how ships don't just appear on the horizon but rise above the curve on the planet B. The fact that shadows change over time would not happen on a flat planet
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How is plate tectonics related to the rock cycle
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Earth materials get melted, buried, lifted, weathers and is pushed by the plate tectonic process. Rocks are this way because of this.
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What is the curie point and why is it important regarding paleomagnetism?
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Temperature when materials lose their magnetic properties, replaced by induced magnetism
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Why was determining longitude so important? Why is it more difficult than determining latitude? How was the problem solved?
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It's the key to oceanic exploration and mapping. Inventing a sturdy clock that ran at a constant rate. A chronometer was the solution.
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How is oceanography different from most of the other sciences?
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It involves many different kinds of sciences and not just one thing specifically. For example, oceanography involves geology.
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Compare the five main oceans.
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Pacific= largest/ deepest Arctic= smallest, shallowest, ice-covered Atlantic= second largest, almost as deep Indian= mainly in southern hemisphere, almost as deep Antarctic Ocean= connects pacific, atlantic, indian oceans and is larger than the atlantic
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What drives plate tectonics?
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Convection in the mantle
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What did we learn about Mars (past and present)
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Today, Mars has no magnetic field but that it's not always been the case. It had 20 to 30x the strength of Earth
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When did Darwin's voyage on the Beagle take place and what was it's focus?
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Focus was to discover many organisms and it took place from 1831-36
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List four ways that early explorers navigated the ocean
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1) following the coast line 2) map of places and general direction 3) using the sun and time of day 4) using the stars
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Who invented the first navigation compass and why was it such a big deal?
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Chinese, it used the magnetic field to determine location and was a reverse tribute
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What was so special about the Challenger expedition in 1872?
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one of the first purely scientific oceanographic expeditions
