Download Lesson 1: The Water Planet

MAR 105 Telecourse
Lesson Summaries & Questions
Lesson 1: The Water Planet
This lesson introduces science itself and explores current scientific ideas about the origins of Earth, its ocean,
atmosphere, and life. It highlights the dramatic effect of vast quantities of liquid water on the nature of planet Earth
and its life. The universe is believed to have begun its present existence 13 to 14 billion years ago in a cataclysmic
event called the big bang. About 5.5 billion years ago, our own sun condensed from a nebula to a protostar to
become a star. Earth was in a liquid state when the planets began to form about 5 billion years ago when density
stratification caused iron to migrate inward forming the Earth’s core while lighter silicates and other matter moved
outward to form the mantle and crust. The early atmosphere formed by outgas-sing. This outgassing, along with
extraterrestrial icy comets, would supply the water that became the ocean. The hypothesis that life originated in
some biosynthetic pathway on the primitive Earth is presented, and the possibility of extraterrestrial origin is posed.
Questions to Answer:
1. Define oceanography and list and briefly describe at least five branches of this science (in text only).
2. Discuss science as a way of understanding the universe and accumulating knowledge. List the steps in the
scientific method and compare and contrast the terms hypothesis, theory, and law as they are used in science (in text
only).
3. Describe why earth is unique in our solar system.
4. Describe the early atmosphere of earth and where the oxygen in our atmosphere came from.
5. Describe two theories of where the water on earth came from.
6. Explain why water was important for the formation of life.
Lesson 3: Making the Pieces Fit
Academics debate the use of the word “paradigm,” but science does have broad over-arching ideas that determine
how the world is viewed, and none permeates oceanography more than plate tectonics. The development of this
theory illustrates the inner workings of scientific discovery, and demonstrates how science influences and is
influenced by society, culture, history, politics, economics, and religion. This first of two lessons devoted to plate
tectonics focuses on the origins and evolution of plate tectonic theory. Based primarily on the fact that the west
coast of Africa and the east coast of South America seem to fit together like the pieces of a puzzle, Wegener
proposed the idea of continental drift in 1912. Wegener’s major problem was the absence of an accepted and proven
mechanism to explain the movement of the continents. Convection, a mechanism that could explain continental
movement, was proposed in the 1920s. But it would take more empirical evidence and much more research before
continental drift could be proven and accepted as a cornerstone of plate tectonic theory. It would take several more
decades of research to develop the complete theory. All the available evidence garnered from years of research was
finally integrated into one overarching idea by John Tuzo Wilson in 1965. While many factors including wind,
water, erosion, and glaciation have combined to create the features of Earth’s surface on land and sea, nothing is as
significant as the effects of plate tectonics.
Questions to Answer:
1. Compare and contrast the classification of Earth's layers based on chemical composition versus their classification
based on physical properties (in text).
2. Describe Wegener’s evidence for the theory of continental drift and how this theory was received in the United
States.
3. Define convection and explain the role it plays in plate tectonics (in text).
4. Compare and contrast the terms continental drift, seafloor spreading, subduction and plate tectonics.
5. Explain how the patterns of paleomagnetism, seafloor age, and sediment thickness contribute to an understanding
of tectonic theory.
Lesson 4: World in Motion
Exploration of plate tectonic theory continues in Lesson 4. The proposals of Hess, Dietz, and Wilson in the 1960s
did not end the quest begun by Wegener. Rather, they fostered an age of vigorous research and debate that continues
today. Lesson 4 focuses on plate boundaries, the continuing accumulation of supporting evidence, and the many
still-unanswered questions. There are three types of plate boundaries—divergent, convergent, and transform.
Divergent boundaries occur where plates spread apart. The mid-ocean ridge systems are the most extensive
divergent boundaries. Convergent boundaries occur where plates collide and melt back into the mantle. These
regions are Earth’s most geologically violent places, marked by powerful earthquakes and explosive volcanoes.
Transform boundaries occur where plates slide past each other. Volcanoes are rare on transform boundaries
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MAR 105 Telecourse
Lesson Summaries & Questions
but, as Californians know, earthquakes abound. Paleomagnetism and apparent polar wandering provide additional
threads of evidence for plate tectonic theory. Further support for the theory is provided by the formation of new
seafloor at the mid ocean ridges and its symmetrical spread in opposite directions. Although many questions about
plate tectonic theory remain, evidence for plate movement is found virtually everywhere it is sought.
Questions to Answer:
1. Compare and contrast deep and shallow earth-quakes.
2. Describe the three major types of plate boundaries and discuss specific examples of each.
3. Describe the formation, movement, and fate of the Hawaiian Ridge and Emperor Seamounts and explain how
these features support the theory of plate tectonics.
4. Discuss the formation of guyots and seamounts and how each is related to tectonic movements.
5. Describe the importance of heat as it relates to plate tectonics.
6. List at least three significant unanswered questions about plate tectonics.
Lesson 5: Over the Edge
Bathymetry, the discovery and study of seafloor contours, has advanced from the use of primitive sounding lines to
sophisticated multibeam sound systems and surface-measuring satellite altimetry. The seafloor is comprised of
continental plates floating in isostatic equilibrium above the denser ocean basin lithosphere. The submerged outer
edges of the continents are called the continental margins, while the deep sea floor beyond is the ocean basin.
Continental margins are classified as passive margins if associated with divergent plates, and classified as active at
the edges of convergent plates. Hydrothermal vents are a feature of the sea-floor associated with ridge formations.
They can form large mineral structures called chimneys, providing a habitat for a newly-discovered biota totally
supported by geochemical energy. The abyssal plain is sediment-covered seabed between the continental margins
and the ocean ridges. Trenches are the deepest part of the seabed, are found at subduction zones, and are typically
seismically active. New bathymetric technology and techniques continue to provide better access to, and more
accuracy in, seabed studies.
Questions to Answer:
1. Describe the features of the continental margin: the continental shelf, shelf break, continental slope, submarine
canyons, and continental rise.
2. Compare and contrast active and passive continental margins.
3. Define the following features of the deep sea: abyssal plains, seamounts, guyots and mid-ocean ridges.
4. Describe the hydrothermal vent phenomenon—how it works, its biological and physical aspects, and its potential
for research and exploitation.
5. Describe the modern techniques and technologies (both shipboard and satellite) used to describe and study the
ocean floor and the variety of specially-designed and instrumented vessels.
Lesson 6: The Ocean’s Memory
Most of the sea floor is covered by layers of sediment of varying thicknesses. These sediments can originate on the
continent and be carried seaward by water or wind; or sediments can be formed from the remains of once-living
terrestrial or marine organisms. Some sediment-sized particles even have extraterrestrial origins. Scientists from
many disciplines study marine sediments to learn of their formation, distribution, or potential as a habitat. Sediments
are also potential oil, gas, and mineral resources. Marine sediments are important as a historical record revealing the
recent history of ocean basins, changes in climate over time, and even of shifts in Earth’s magnetic field. Sea floor
sediment collection and description was part of many early expeditions using a variety of sampling devices and
techniques. Today’s technology includes state-of-the-art drillships and seismic bottom profilers. The study of
marine sediments employs essentially the same techniques and standards devised by terrestrial geologists:
appearance, particle size, origin of the material, distribution, and sample location. Color and overall appearance is
important, as is the particle size. A number of deep-sea drilling projects are currently active for scientific or
commercial reasons; the best and best-equipped presently being the Ocean Drilling Project (ODP) using the JOIDES
vessel Resolution.
Questions to Answer:
1. Describe the major types of sea-floor sediment (terrigenous, hydrogenous, biogenous), how they form and where
they are found.
2. Compare and contrast the sediments of the continental margins and those of the deep-sea floor (briefly in video, in
text).
3. What is an ooze and where are they found (in text).
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MAR 105 Telecourse
Lesson Summaries & Questions
4. Discuss some of the commercial and economic interests in marine sediments.
5. Explain how knowledge of marine sediments can aid in describing Earth’s historical climatic changes and
magnetic field orientation.
Lesson 7: It’s in the Water
Water is an extraordinary substance with a number of unique properties. It exists naturally on Earth in all three
phases; its solid phase floats on its liquid phase; it can absorb or lose great quantities of heat with only a gradual
change of temperature; and it is a remarkably good solvent. These unusual properties are related to the polarity of
water’s molecules and the resulting hydrogen bonds water molecules form. Hydrogen bonds inhibit molecular
movement, which has a dramatic effect on the thermal properties of water and accounts for the moderating effect of
water on climate. Temperature and salinity are the two main factors that affect the density of sea water. The sinking
of denser water and rising of less dense water drives the thermohaline circulation of the ocean. Many of the salts of
the ocean are leached from the land and carried to the ocean as run-off. They also rain in from the atmosphere, enter
from hydrothermal vents and volcanoes, percolate up from groundwater, and dissolve out of underlying sediments.
The three most abundant dissolved gases are nitrogen, oxygen, and carbon dioxide. Nitrogen is the most abundant
gas in seawater but only a few microorganisms can utilize it directly. Oxygen enters the ocean at or near the surface
where it mixes in from air. It is also produced by photosynthesis. Carbon dioxide is abundant in seawater. It is
consumed by photosynthesis and is the major regulator of ocean pH.
Questions to Answer:
1. Describe the structure and polar nature of water molecules and explain how these contribute to adhesion,
cohesion and the dissolving power of water
2. Describe why ice floats and why this is important.
3. Describe the sources that add salts to the ocean and the sinks that remove salts from the ocean.
4. Describe the factors that regulate the density of seawater and explain the nature and importance of thermohaline
circulation.
5. Define heat capacity and explain why it is important to the global thermostatic effects of water (see Sect 6.4 &
6.8 in text)
6. Explain the relationship between carbon dioxide and the greenhouse effect and the interplay of oceanic and
atmospheric carbon dioxide in global warming. Explain why some scientists believe that adding iron to the oceans
could affect atmospheric carbon dioxide and global warming.
Lesson 8: Beneath the Surface
This lesson examines some aspects of the ocean’s structure and explores the characteristics of light and sound in the
ocean. The stratification of the ocean is a result of density differences related to salinity and temperature. Much of
the ocean is divided into three temperature zones—a surface zone, a middle thermocline zone, and a deep zone.
About 80 percent of the ocean is the deep zone with temperatures ranging from –1°C to 3°C. The surface or mixed
zone that is warmed by the sun contains about two percent of the ocean’s water and extends to a depth of about 150
meters. The ocean is also layered by light penetration. Solar radiation heats the upper ocean, powers
photosynthesis, and has important effects on biology. Sunlight attenuates as it passes through seawater creating
three zones defined by light intensity (euphotic, disphotic and aphotic). Integrating light, temperature, and other
factors, the ocean can be subdivided into five zones: the epipelagic, mesopelagic, bathypelagic, abyssopelagic, and
hadopelagic zones. Marine organisms with vision are adapted to the ambient light of their depth zones. The passage
of sound through water is more efficient than the passage of light, so many marine animals rely more heavily on
their hearing than their vision. Understanding the relationships between light and sound and the physics, chemistry,
and biology of the oceans provides a better understanding of the oceans themselves and the organisms that inhabit
them.
Questions to Answer:
1. Describe the general density stratification of the oceans and explain why it exists and how it differs in tropical,
temperate, and polar oceans (in text).
2. Compare and contrast the euphotic, disphotic, and aphotic zones of the ocean.
3. Compare and contrast the following ocean zones: epipelagic, mesopelagic, bathypelagic, abyssopelagic, and
hadopelagic.
4. Discuss how the quantity and wavelength of light changes as it passes through seawater and list some ways this
affects marine life.
5. Describe three factors that affect the speed that sound travels in the ocean and how each affects sound speed.
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MAR 105 Telecourse
Lesson Summaries & Questions
Lesson 9: Going to Extremes
Integrating several principles of oceanography, students compare and contrast polar and tropic oceans. Marked
differences in temperature, light, and other features allow the application and integration of several physical and
chemical principles. This requires them to apply principles from the first eight lessons. With no substantial new
block of text reading, students must review back-ward and glance forward to integrate facts, apply principles, and
create understanding. The major process driving all ecosystems is primary productivity, which is accomplished by
photosynthesis in most ecosystems. The major oceanic primary producers are the phytoplankton and the major
factors that regulate the rate of primary production are light and nutrients. Nitrogen and phosphorous are often the
key nutrients of primary production and are generally most abundant in deep waters, while sunlight is available only
near the surface. Without both light and nutrients, photosynthetic productivity is low or impossible. Whereas
tropical ecosystems are regulated by nutrient availability, polar ecosystems are regulated more by the availability of
light. When the sun is shining, polar regions exhibit some the highest productivity in the oceans. Both polar and
tropical ecosystems share a problem with all regions of the ocean; the ever-increasing demands of the burgeoning
human population.
Questions to Answer:
1. Define primary production and compare and explain the patterns of production in polar and tropical oceans.
2. Explain the structure of coral animals and coral reefs.
3. Define biodiversity; compare and contrast biodiversity in polar oceans and on coral reefs.
4. Explain the symbiotic relationship between symbiotic dinoflagellates (a type of algae) and the coral polyps they
inhabit.
5. List and give examples of several ways organisms cope with the long dark season of polar oceans.
6. Discuss several uses, abuses, and problems specific to coral reefs and to polar ecosystems.
Lesson 10: Something in the Air
Study of the whole Earth system—the inseparable interaction between the ocean, the atmosphere, and the land—
begins with the atmosphere and how it is affected by the ocean. Earth’s lower atmosphere is composed of nitrogen,
oxygen, some minor gases, and varying amounts of water vapor. These factors interact to become part of an active
system, which is powered by radiant energy from the sun. Nearly all weather events result from complex
interactions between the atmosphere and the ocean. Solar energy is received and re-radiated from Earth in varying
amounts, depending on latitude. Water and air move large amounts of heat energy between the equator and the
poles as convection currents. These winds form more-or-less stable, predictable patterns known as the trade winds,
doldrums, westerlies, and horse latitudes. When different kinds of air masses collide, a front may be formed and
storms may result. The most common type of storm is the cyclone, with various sub-categories including hurricanes,
tropical cyclones, and extratropical cyclones. Using new technologies such as Doppler radar, weather satellites, and
computer modeling, scientists continue to gather information about Earth’s system, and how its components interact.
These, and other tools, are helping meteorologists understand the building blocks of weather, with an eye toward
more accurate long-range prediction. For the future, meteorologists must consider the effects of global warming on
the system, and thus on the human population.
Questions to Answer:
1. Describe the molecular composition of Earth’s lower atmosphere, the fluctuating amount of water vapor, and how
all of this influences air’s density.
2. Describe differences in the amount of solar heating that reaches different parts of the earth and how this leads to
convection and atmospheric circulation.
3. Describe the three major types of atmospheric convection cells—Hadley, Ferrel, Polar.
4. Describe the tradewinds – where they are found and what causes them.
5. Describe what causes the Coriolis Effect and how it influences atmospheric conditions.
6. What is the ITCZ and why is it important?
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