Oceanography notes, page



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OCEANOGRAPHY NOTES, PAGE



I. The Origins of Oceanography
- Oceanography is the study of the oceans

- includes studies of biology, geology, hydrology, chemistry and physics

- although the scientific exploration of the World's oceans has only taken place during the past two hundred years, the oceans have influenced humans for tens of thousands of years
A. Early Mariners of the Pacific

- colonization of the Pacific originated from Asia


1. Australia

- may have been first settled approximately 50-70 thousand years ago

- may have been settled from "accidental" sea voyages by rafts or logs but these early explorers would be floating against the currents and there is one open-water crossing of more than 50 miles

- by 10 thousand years ago aboriginal peoples had settled in all major environmental zones


2. Oceania

- the islands of the Pacific were probably explored for trade and colonization; the colonization of Oceania was from Asia

- extensive knowledge of winds, stars and currents allowed colonization of tiny islands throughout the Pacific (subsequently with about 1000 Austronesian languages developing in isolation on these islands)

- Polynesians probably originated from Taiwan or eastern China; using double-hulled canoes, they voyaged eastward against the prevailing winds, took women and children, and carried livestock, seedlings and rootstock


B. Early Mariners of the Mediterranean

- conducted widespread trade with Europe, the Near East and northern Africa (metals, textiles, pottery, olive oil, wine, etc.)

- Mediterranean maritime cultures include the Minoans (bronze-age mariners from the island of Crete; approximately 2800 to 1450 BC), the Mycenaeans (late Bronze Age of central and southern Greek mainland; 1600-1100 BC), the Greek City-States (iron-age peoples; approximately 700 to 338 BC), and the Phoenicians (1,200 - 333 BC; from coast of Lebanon and northern Israel but settled all over the Mediterranean)
C. The Chinese Exploration of the Pacific and Indian Oceans

- between 1405 and 1433 the Ming emperors organized seven exploratory voyages in the Indian and Pacific Oceans, involving 37,000 men and 317 ships; headed by Admiral Cheng Ho (Zheng He); the purpose of the voyages was to expand Chinese influence in the region

- primarily due to economic problems, the Chinese ended their discovery voyages and increasingly became isolated from the rest of the World
D. Exploration of the Atlantic
1. The Vikings

- Scandinavian agriculturalists, traders and raiders

- warming of climates during the late 9th Century AD freed the North Atlantic of ice and the Vikings colonized Iceland; Greenland was colonized by 995 AD

- in 995 AD Leif Eriksson sailed westward from Greenland and discovered Vinland (Eastern Canada and/or the northeastern United States); Vikings settled in Newfoundland, until driven off by Native Americans, with final abandonment of the colony around 1020 AD

- deteriorating climate in the North Atlantic prevented any further attempts at colonization by the Vikings
2. The "Age of Discovery"

- Renaissance Europeans began major World exploration voyages during the 1400's, primarily due to the disruption of commerce by the Turks, who captured Constantinople (Istanbul, Turkey) in 1453


a. Henry the Navigator

- Portuguese prince who financed many small expeditions between 1451 and 1460, the purpose of which was to increase the wealth of Portugal and spread Christianity

- his captains carried Compasses (instruments that point to magnetic north) for navigation purposes
b. Christopher Columbus

- "discovered" America on October 12, 1492 for Spain; the original purpose of the voyage was to find an easier trade route to the "spice islands" of India and China


c. Ferdinand Magellan

- began attempt at circumnavigation of the globe on 20 September, 1519; killed by natives in the Philippines, but Sebastian del Caño completed the circumnavigation on 6 September, 1522

E. The Formative Years of Marine Science
1. Latitude, Longitude and the Invention of the Chronometer
a. Map coordinates

- the Earth is divided into a system of imaginary lines called parallels and meridians


Meridians - pass through the poles; Greenwich (Prime) Meridian is the 0° meridian; International Date Line is the 180° West/180° E meridian; Longitude is the reference coordinate of meridian, and is oriented in a north-south direction (but divides the Earth east-west)
Parallels - lines parallel to equator; Latitude is the reference coordinate of a parallel; in east-west direction (but divides the Earth north-south); Equator is at O° latitude; Poles are at 90° latitude
b. Determination of Latitude

- is relatively easy; you can determine latitude by using a Sextant, which measures angles from the horizon to selected stars (especially Polaris, the North Star), planets, the Moon and the Sun


c. Longitude

- early determinations of East-West position was by ascertaining ships speed, by throwing a log attached to a rope over the side of the ship and counting the number of knots that ran out when all the sand had run through an "hour glass" (Nautical miles, or Knots, are still used as units of measure; 1 Knot = 1.15 statute miles per hour, or 0.51 meters per second)

- the Earth takes 24 hours to complete a 360° rotation, so the Sun appears to move 15° each hour across the Sky; therefore, you can determine your longitudinal position if you compare your local "noon time" with that of Greenwich, England (the Prime Meridian); but to determine your exact position you need a good Chronometer ("clock")
John Harrison - English clockmaker; built a series of chronometers between 1735 and 1761 which would solve problems of determining longitudinal position
d. Early Determinations of Water Depth

- to determine water depth (and ship's location) sailors threw in a lead weight coated with sticky wax and attached to a rope; by comparing the type of material sticking to the weight and charts, you could determine your approximate position

- depths were measured in Fathoms (distance between tips of middle fingers of outstretched arms of a large man; 6 feet or 1.8 meters)
e. Other Important Units of Measure
1 kilometer (km) = 103 meters = 0.621 statute miles = 0.540 nautical miles

1 meter (m) = 102 centimeters = 39.4 inches = 3.28 feet = 1.09 yards = 0.547 fathom

1 centimeter (cm) = 10 millimeters = 0.394 inch = 104 micrometers

1 micrometer (µm) = 10-3 millimeter = 0.0000394 inch

1 kilogram (kg) = 103 grams = 2.205 pounds
2. Captain James Cook (1728-1779)

- undertook three great voyages between 1768 and 1780 that covered the entire Pacific basin, from the Bering Strait (entrance to Arctic Ocean) to the Antarctic region

- Cook "discovered" the South Georgia Islands, South Sandwich Islands, and Hawaiian Islands (where he was killed by natives in 1779)

- his explorations showed that long ocean voyages were possible; he conquered the disease scurvy (by providing vitamin C in the form of fruit for his crews), sampled subsurface water temperatures, measured winds and currents, made many determinations of ocean depths (termed Soundings), and collected important data on coral reefs, fauna, flora, etc.


3. Benjamin Franklin (1706-1790)

- as deputy postmaster general for the American Colonies, used information obtained from mail ships to publish a map of the Gulf Stream in 1777


4. Matthew Fontain Maury (1806-1873)

- U. S. naval officer in charge of the Depot of Naval Charts and Instruments

- Maury prepared accurate charts of winds and currents, that were summarized in his book The Physical Geography of the Sea (1855)
5. Georg Forchhammer

- Danish geologist; published first major paper of seawater chemistry in 1865

- Forchhammer found that although salinity varies greatly, the proportions of salts in seawater remains the same
6. The Development of Marine Biology
a. Christian Gottfried Ehrenberg (1795-1876)

- German naturalist

- in the early to mid-1800's Ehrenberg described many microscopic organisms, concluding that many skeletal remains found on the ocean floor are from organisms that spent their life floating along the sea surface
b. Sir John Ross (1777-1856)

- British naval officer and explorer

- John Ross's expedition measured Arctic Ocean depth in 1817-1818 around Baffin Bay, Canada; his crew also sampled bottom sediments and fauna
c. Sir James Clark Ross (1800-1862)

- British naval officer and explorer (and nephew of John Ross)

- his expeditions measured ocean depth around the Antarctic in 1839-1843; studied bottom sediments and fauna, concluding that the same species are found in the Arctic and Antarctic
d. Edward Forbes (1815 - 1854)

- British naturalist who investigated the vertical distribution of organisms in the sea

- Forbes concluded that very little, if any, life could exist at great ocean depth (it is now known that this conclusion is wrong)
e. Charles Darwin (1809-1882)

- British; was ship's naturalist on the HMS Beagle, that mapped the coast of South America, explored various islands, and circumnavigated the globe between 1831 and 1836

- described the formation of coral reefs in 1843

- based largely on his studies conducted as ship's naturalist on the Beagle, published Origin of Species in 1859, defining evolutionary theory


f. Victor Hensen (1835-1910)

- German scientist; coined the word "plankton"

- during an 1889 expedition, showed that there is more plankton in cold waters than warm waters (this was unexpected)

F. Major Marine Scientific Expeditions


1. Challenger Expedition (British; 1872 - 1876)

- most successful oceanographic expedition; had a staff of six scientists under the direction of C. Wyville Thompson (1830-1882)

- objectives were to determine the physical features of the ocean basins, chemical composition of seawater at all depths, the origin of sea floor deposits, and the distribution of organisms at all depths in the sea and on the ocean floor

- fulfilled all of these objectives; the findings of the expedition were published in 50 large volumes, including the description of 4717 new species of marine life


2. The Fram Expedition

- Norwegian expedition undertaken by Fridtjof Nansen (1861-1930) and 12 other expedition members

- on September 21, 1893 they allowed the Fram to freeze into the sea ice of the Arctic Ocean, and drifted with the pack ice across the Arctic Ocean until the ship was released on August 13, 1896

- work by Nansen and other Scandinavian scientists led the way in the development of physical oceanography during the early twentieth century


3. Current Large-Scale Oceanographic Research
a. Deep Sea Drilling Project (DSDP)

- 1963-1983; headed by the Scripps Institution of Oceanography, California

- Scripps and several other institutions joined together to form the Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES), which used the Glomar Challenger to drill deep cores to determine the history of the ocean basins
b. Ocean Drilling Program (ODP)

- 1983-2003; supervised by Texas A & M; used the drilling ship JOIDES Resolution to determine the composition and history of both ocean basins and continental margins


c. Integrated Ocean Drilling Program (IODP)

- began in 2003, led by the United States and Japan; uses the drilling ship Chikyu to collect geologic cores and to formulate the history of the ocean basins, including properties of the deep crust, climate change, earthquake mechanisms, and the microbiology of the deep ocean floor; the Chikyu is capable of drilling 7,000 meters (23,000 feet)


d. Geochemical Ocean Sections (GEOSECS)

- expedition organized to study ocean circulation patterns, ocean mixing processes, and biogeochemical cycles

- GEOSECS was an international study conducted as part of the International Decade of Ocean Exploration 1971-1980 (IDOE), with surveys in the Atlantic (July 1972-May 1973), Pacific (August 1973 - June 1974) and Indian Ocean (December 1977 - March 1978)
4. Obtaining Information about the Ocean Basins
a. Research Ships

- there are approximately 1000 oceanographic research ships today

- Often contain shipboard laboratories, towing and lifting equipment, side thrusters for maintaining ship position, drilling and coring equipment, computers for analyses of data, and satellite radio navigation systems
b. Submergence
Scuba Gear - can be used to water depths of approximately 40 meters (with special gas mixtures, can dive up to 300 meters)
Underwater Habitats - for long-term experiments and for testing the feasibility of colonization of the oceans
Deep-Sea Submersibles - include bathyscapes, submarines, rescue vehicles and mid-water drifters
c. Sampling Sediments
c1. Depth Recording
Bathymetry - measurement of the ocean depths and topography of the sea floor

- bathymetery is measured primarily by SONAR (sound waves bounced off the sea floor; measure elapsed time to determine water depth)


- Echo Sounders send sound signals (termed "pings") into the ocean to produce echoes when the sound bounces off any density differences, such as marine organisms or the ocean floor; may use Multibeam Echo Sounders (use multiple frequencies of sound simultaneously) and Side-Scan Sonar (towed behind a ship on a cable)
c2. Dredging and Grab Samplers

- dredging nets are towed along the bottom, and then lifted by an electric winch

- grab samplers have a spring-loaded trap door; the sampler is sent to the bottom, where it digs into the sediments and clamps shut
c3. Coring
- Gravity Corers consist of a hollow pipe; it is sent to the bottom where it gathers cores up to several meters long
- Piston Corers have a piston, to prevent compaction of sediments; can produce cores up to 12 meters long
- Platform Drilling with rotary drilling rigs can produce cores more than 1000 meters long
d. Properties of the Ocean Crust
d1. Heat Conduction

- heat probes measure heat flow

- the internal heat of the Earth is produced primarily from radioactive decay and due to the geothermal gradient (increased heat with rock depth)
d2. Rock Magnetism

- ancient magnetism is preserved in iron-bearing rocks and sediments

- measured by magnetometers
d3. Gravity Anomalies

- the mass of the Earth is not the same at all points

- gravity anomalies are used to determine differences between rock properties
d4. Seismic Profiling

- determine properties of rock and sediments on the ocean floor by seismic waves reflected or refracted by them

II. Earth and Its Ocean
A. Origin of the Universe
- the universe is believed to be approximately 10 - 20 billion years old
1. Age Estimation is Based Upon:
a. Star Observations

- observation of star clusters and interpretation of nucleosynthesis (study of element formation, especially in massive stars) suggests that the universe is about 15 to 20 billion years old


b. Hubble's Law (Law of Redshifts)

- the velocities at which galaxies move away from us are proportional to their distance from us; more and more remote galaxies will have greater and greater speeds of recession

- based on the Law of Redshifts, it is believed that the universe is 10 to 20 billion years old (recent studies indicate about 13.7 billion years old)

b1. According to Hubble's Law, the universe is expanding


b2. At the "beginning of time" all energy and matter in the universe was crowded together at a single point
b3. The Big Bang

- the event that created the Universe; it generated the expanding motion that we observe today


Inflationary Models of the Universe suggest that the Universe may have originated in a "False Vacuum", in which gravity was a repulsive force (at this time the Universe would have been trillions of times smaller than a proton, but negative gravity "inflated" the Universe, cooled it, and released huge amounts of energy which became the Big Bang)

- Inflationary Models suggest that there are not several independent forces in the universe (these are aspects of a single unified force; Grand Unified Theory, or GUTs)

2. Universe Expansion or Collapse?

- older theories stated that the total matter and energy of the universe creates gravitation, which will slow the expansion of the universe through time

- however, recent studies indicate that the rate of expansion is actually increasing, which suggests the existence of an unknown force (Dark Energy); dark energy may account for 3/4 of the total mass-energy of the universe
B. Stars and Galaxies
1. Star Lives

- stars produce energy by nuclear fusion and gravitational contraction or collapse

- the larger the star, the shorter it's lifetime; also, the mass of a star determines it's evolutionary history

- elements as massive as iron can be made in energy-producing reactions in stars

- more massive elements are made by the reaction of neutrons with nuclei, especially due to Supernova Explosions (these are extremely energetic explosions due to the collapse of the core of a massive star)

- our Solar System (including our Sun, the planets, and ourselves) are made from the remnants of previous supernova explosions


2. Galaxies

- astronomical bodies made of billions of stars, as well as abundant interstellar gas and dust (also evidently containing substantial "dark matter", material that is invisible at all wavelengths)

- our galaxy (the Milky Way) began as a sphere about 8 to 15 billion years ago with contraction of hydrogen and helium gas; collisions between gas clouds flattened the galaxy and condensation and accretion of stars began to take place
C. The Solar System
1. Overview of the Solar System

- our Solar System consists of the Sun, planets, their moons, and other bodies that orbit the Sun


a. The Sun

- constitutes approximately 1000 times the mass of all other solar system bodies combined; made of approximately 71% hydrogen and 27% helium


b. The Planets

- includes Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune


b1. Terrestrial Planets

- Mercury, Venus, Earth, Mars; small and dense (3.9 to 5.5 gm/cm3); made of rocky material (mostly silica; also iron, aluminum, magnesium, sulfur); not much hydrogen and helium, no rings, few satellites; lie in inner part of solar system
b2. Jovian Planets

- Jupiter, Saturn, Uranus, Neptune; made mostly of volatile material (easily vaporized; dominated by gases, liquids, and ice in form of hydrogen, helium, ammonia, methane); probably with relatively small cores of iron and rock; large and low density (0.71 to 1.67 gm/cm3); lie in outer part of solar system; with ring systems and large satellite systems; probably grew rapidly from icy material; grew dense enough to attract vast amounts of nebular gas
b3. Minor Planets (Dwarf Planets)

- Pluto and it's "moon" Charon are now considered to be "Minor Planets"; they are probably remnant planetesimals from the birth of the Solar System

- Pluto completes its highly elliptical orbit (which is out of the ecliptic plane) in approximately 248 years; the axis of rotation nearly lies in it's orbital plane

- Pluto is made of rock mixed with ices (water, nitrogen, methane)


c. Other Solar System Features
c1. Satellites (Moons)

- Terrestrial Planets have few satellites, Jovian have many

- Moons have approximately circular paths and most lie in equatorial planes corresponding to the Ecliptic (the plane of the orbit of the planets around the Sun)

- most Moon formation was probably similar to that of planets


c2. Asteroids

- rocky or metallic bodies with diameters from a few meters up to approximately 1000 kilometers across

- most orbit the Sun within the Asteroid Belt between Mars and Jupiter
c3. Comets

- icy bodies less than 10 kilometers across that "grow" huge tails as they near the Sun and are vaporized by it's heat; are the source of most meteors

- most comets orbit far beyond Pluto in the Oort Cloud
2. Formation of the Solar System

- there was a lot going on before our Solar System began (all elements in our Solar System that are heavier than iron needed prior supernovae explosions to form)

- abundances of isotopes in meteorites show that the solar nebula existed about 4.6 billion years ago and that only 10 to 100 million years was required to form the planets
a. Solar Nebula Hypothesis

- Solar System probably began as a slowly rotating cloud of gas and dust

- gases and dust condensed and clumped to form planetesimals; planetesimals aggregated to form planets and their satellites (moons); dates of oldest rocks on the Earth's Moon and the oldest Meteorites cluster at about 4.6 Ga

- rocky and metallic material condensed to form planets in the hot inner portion of the Solar System; lighter gases and ice condensed in the cold outer portions of the Solar Nebula to form huge planets

- late impact of planetesimals cratered the surfaces of the planets and moons, and may have tilted the rotational axes of some planets

- some planetesimals survive to this day as asteroids and comets


b. Origin of the Earth and the Archean Eon
Archean Eon = approximately 4.5 billion to 2.5 billion years before the present
- heat from bolide impacts and radioactive decay produced a molten planet, in which the densest material sank toward the center and the least dense rose toward the surface (produced an iron core and a silicate-rich mantle)

- the less dense silicates floated to the surface, forming a "magma ocean", which cooled to form a silicate-rich crust (this was a precursor to the oceanic crust of the modern world)


D. The Atmosphere was Formed By:
1. Degassing of Earth's interior

- an initial atmosphere was probably formed during differentiation, then "swept away" when the early Solar System was cleared of debris by a strong "Solar Wind" (charged particles moving away from the Sun)

- volcanic activity then produced a second atmosphere of water vapor, hydrogen, hydrogen chloride, nitrogen, carbon dioxide, carbon monoxide (and secondary chemical reactions in the atmosphere produced methane and ammonia)
2. From Comets/"Space Ice"

- comet-like material supplies ammonia, methane, water vapor, etc. to partially create the atmosphere


3. Photosynthesis

- early photosynthetic organisms, such as blue-green algae (cyanobacteria), create oxygen

- but there was evidently little "free" oxygen before about 2 billion years ago
E. The Oceans

- the Earth's interior degasses, gases condense in the atmosphere during Earth cooling, and precipitation forms and falls to Earth to form oceans

- the salinity of the Ocean was created by weathering rocks on land

- seawater has varied little in salinity since the Early Archean (although the relative proportions of dissolved ions has varied significantly)

- the Early Archean ocean was probably much warmer than that of today due to the presence of abundant radioactive elements in the Earth's crust and the "Greenhouse Effect"

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