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Oceanography
An Invitation to Marine Science, 7th
Tom Garrison
Chapter 1
Origins
What is Marine Science/
Oceanography?
• The process of discovering unifying
principles in data obtained from the ocean,
its associated life- forms, and its bordering
lands.
• It integrates geology, physics, biology,
chemistry, and engineering.
Earth Is an Ocean World
Sunrise on an ocean world. A liquid-water ocean moderates temperature and
dramatically influences weather, nurtures life, and provides crucial natural
resources.
What is the Ocean?
• The ocean is the vast body of saline water
that occupies the depression of Earth’s
surface.
• In reality there is only one world ocean!
Earth Is an Ocean World
• Covers 361 million sq km (139
million sq miles) of Earth’s
surface.
• Averaging 3,796 meters
(12,451 feet) deep.
• A mass of 1.41 BILLION tons.
Earth Is an Ocean World
Average ocean depth is 4 ½ times as great
as average land elevation.
Mid-Atlantic
Ridge
Ocean’s
deepest
spot
Earth’s
highest
mountain
Pacific Ocean Basin,
Earth’s largest feature
Stepped Art
Fig. 1-2, p. 5
Earth Is an Ocean World
The relative amount of water in various locations on or near Earth’s surface.
More than 97% of the water lies in the ocean.
Quick Question…
LOOK AT THE MAP OF
FLORIDA…
Marine Scientists Use the Logic
of Science to Study the Ocean
Marine Science (or oceanography)
integrates many different types of science:
• Marine geologists study Earth’s crust and composition.
• Physical oceanographers study of waves, currents, and
climate prediction.
• Chemical Oceanographers study the ocean’s dissolved
gases and solids in the ocean.
• Climate Specialists investigate the ocean’s role in Earth’s
changing climate.
• Marine biologists study the nature and distribution of marine
organisms.
• Marine engineers design and construct structures used in or
on the ocean.
Marine Scientists Use the Logic
of Science to Study the Ocean
Oceanographers deploy a mooring containing temperature probes from the
deck of R/V Oceanus during a gale off Cape Hatteras.
Marine Scientists Use the Logic
of Science to Study the Ocean
• Science is a systematic process of asking
questions about the observable world by
gathering and studying information (data)
• Science interprets raw information by
constructing a general explanation with
which the information is compatible.
• Scientists start with a question based upon
something observed or measured.
• Working hypothesis – tentative explanation
for the observation or measurement that can
be tested and verified by further observations
and controlled experiments
Marine Scientists Use the Logic
of Science to Study the Ocean
• An experiment is a test that simplifies
observation in nature or in the laboratory by
manipulating or controlling the conditions
under which the observations are made.
• Theory – a hypothesis consistently
supported by observation or experiment.
• Laws – larger constructs that summarize
experimental observations.
• A law summarizes observations while a
theory provides an explanation for the
observations.
The Scientific Method
An outline of the scientific method, a systematic process of asking questions
about the observable world and then testing the answers to those questions.
Curiosity
A question arises about an event or
situation: Why and how does this
happen? Why are things this way?
Law
Theories can evolve into larger
constructs: laws. Laws explain events in
nature that occur with unvarying uniformity under identical conditions. Laws
summarize experimental observations.
Observations, measurements
Our senses are brought to bear: What is
happening? Under what circumstances?
When? How does it operate? Does there
appear to be a dependable cause-andeffect relationship at work?
Theory
Patterns emerge. If one or more of the
relationships hold, the hypothesis
becomes a theory, an explanation for
the observations that is accepted by
most researchers.
Hypothesis
A tentative explanation is proposed.
Controlled experiments are planned to
prove or disprove potential cause-andeffect relationships. A good hypothesis
can predict future occurrences under
similar circumstances.
Experiments
Tests are undertaken in nature or in
the laboratory. These tests permit
manipulating and controlling the
conditions under which observations
are made.
Stepped Art
Fig. 1-4, p. 7
Stars and Seas
• To understand the ocean, we need to
understand how it formed and evolved
through time.
• Because the world ocean is the largest
feature of Earth’s surface, scientists believe
the origin of the ocean is linked to Earth’s
origin.
• The origin of Earth is linked to that of the
solar system and the galaxies.
Earth Was Formed of Material
Made in Stars
• The universe apparently had a beginning
called the big bang that occurred ~13.7
billion years ago.
• All of the mass and energy of the universe
was concentrated at a geometric point at the
beginning of space and time, the moment
when the expansion of the universe began.
• We don’t know what initiated the expansion,
but it continues today and will probably
continue for billions of years, perhaps forever.
Stars and Planets are Contained
within Galaxies
Our Milky Way Galaxy pictured from afar. We’re inside and dust obscures our
view, but this painting is a good guess about what our galaxy looks like, based
on many different types of observations. Our solar system is a little more than
half-way out from the center in one of the blue spiral arms.
Stars and Planets Are
Contained within Galaxies
• What do stars have to do with the ocean?
• Most of the substance of Earth, its ocean,
and all living things, was formed by stars.
• Every chemical element heavier than
hydrogen was manufactured and released
into space by stars.
• Our sun, like all normal stars, is powered by
nuclear fusion.
Stars and Planets Are
Contained within Galaxies
A filament of hot gas erupts from the face of our sun. Like all normal stars, the
sun is powered by nuclear fusion – the welding together of small atoms to
make larger ones. The entire Earth could easily fit into this filament’s
outstretched arms.
Stars Make Heavy Elements
from Lighter Ones
The origin of a solar
system in the spiral
arm of a galaxy. Our
sun and its family of
planets were formed in
this way about 5 billion
years ago.
Solar Systems Form by
Accretion
Planet-building in progress. Accretion of planets occurs when small particles
clump into large masses.
Earth Accumulated in Layers
Sorted by Density
• How did Earth become density stratified?
• Young Earth was probably homogeneous
• Heat and gravitational pressure caused Earth
to partially melt
• Gravity then pulled the iron present into the
center of Earth
• This heated Earth further and lighter minerals
migrated to Earth’s surface and formed the
crust
Earth Accumulated in Layers
Sorted by Density
(top) The planet grew by the aggregation
of particles. Meteors and asteroids
bombarded the surface, heating the new
planet and adding to its growing mass.
At the time, Earth was composed of a
homogeneous mixture of materials.
(middle) Earth lost volume because of
gravitational compression. High
temperatures in the interior turned the
inner Earth into a semisolid mass; dense
iron (red drops) fell toward the center to
form the core, while less dense silicates
move outward. Friction generated by this
movement heated Earth even more.
(bottom) The result of density
stratification is evident in the formation of
an inner and outer core, a mantle, and
the crust.
Earth Accumulated in Layers
Sorted by Density
• How did water and water vapor form on early
Earth?
• The Sun stripped away Earth’s first
atmosphere
• Gases, including water vapor, released by
the process of out-gassing, replaced the first
atmosphere.
• Water vapor in the atmosphere condensed
into clouds.
• Eventually, the surface cooled enough for
water to collect in basins.
Earth Accumulated in Layers
Sorted by Density
Comets may have delivered some of Earth’s surface water. Intense bombardment
of the early Earth by large bodies – comets and asteroids – probably lasted until
about 3.8 billion years ago.
Earth Accumulated in Layers
Sorted by Density
The early atmosphere was very different from the atmosphere today.
Life Probably Originated in the
Ocean
Fossil of a bacteria-like
organism (with an
artist’s reconstruction)
that photosynthesized
and released oxygen
into the atmosphere.
Among the oldest
fossils ever discovered,
this microscopic
filament from
northwestern Australia
is about 3.5 billion
years old.
What Will Be the Future of Earth?
• How long can Earth exist?
• Our Sun will begin to die in 5 billion years.
• 6 billion years from now the sun will enter the
red giant phase and will engulf the inner
planets.
• At that time, Earth will probably be recycled
into component atoms.
• See Figure 1.8 for a timeline of Earth.
What Will Be the Future of Earth?
Are There Other Ocean Worlds?
• Where have scientists found evidence of
water?
• Europa
– The gravitational pull of Jupiter twists Europa,
cracking the ice crust and warming the interior.
– In some areas the ice has broken into large
pieces that have shifted away from one another
but fit together like a jigsaw puzzle.
– This suggests the ice crust is lubricated by slush
or water. A global ocean greater in volume than
Earth’s ocean may lie beneath the movable
crust. It may also be salty - salinity has been
detected by Galileo’s magnetometers.
Are There Other Ocean Worlds?
In 2005, Europe’s Mars Express orbiter imaged a glacier in an unnamed crater in
the vast plains of northern Mars. This 200 meter (656 foot) thick remnant of a
larger ice sheet is shielded by the frosty shade of the crater walls.
Are There Other Ocean Worlds?
• Where have scientists found evidence of
water?
• Titan – Saturn’s largest moon, may have an
ocean of hydrocarbons.
• Mars
– Early in its history, Mars may have had a thick
atmosphere of carbon-dioxide, much like the
atmosphere of the early Earth.
– An ocean may have existed on Mars about 3.2
billion years ago.
– Over the eons, rocks on the Martian surface
absorbed the carbon dioxide and the atmosphere
grew thin and cold and the ocean disappeared
Chapter 1 Main Concepts
• Science is a systematic process of asking questions about the
observable world by gathering and then studying information. Science
interprets raw information by constructing a general explanation with
which the information is compatible. Explanations (theories) may change
as our knowledge and powers of observation change; thus, all scientific
understanding is tentative.
• The universe’s observable mass consists mostly of hydrogen atoms. The
heavy elements we see around us were constructed in stars. Our solar
system is the result of the accumulation of elements formed in stars and
distributed into space by cataclysmic events at the end of their lives.
• Earth is density stratified – that is, as Earth formed, gravity pulled the
heaviest materials (iron, nickel) to its center as lighter minerals rose to
the surface. Earth’s first solid surface formed about 4.6 billion years ago.
• Though most of Earth’s water was present in the solar nebula during the
accretion phase, a barrage of icy comets or asteroids from the outer
reaches of the solar system colliding with Earth may also have
contributed a portion of the ocean-to-be.
• Life probably originated in the ocean.
• Water, even liquid water, appears to be present in a few other places in
our solar system.
Chapter 1 in Perspective
In this chapter you learned that Earth is a water planet, possibly one of few in the galaxy. An ocean
covering 71% of its surface has greatly influenced its rocky crust and atmosphere. The ocean
dominates Earth, and the average depth of the ocean is about 4½ times the average height of the
continents above sea level. Life on Earth almost certainly evolved in the ocean; the cells of all life
forms are still bathed in salty fluids.
We study our planet using the scientific method, a systematic process of asking and answering
questions about the natural world. Marine science applies the scientific method to the ocean and the
living organisms dependent on the ocean.
Most of the atoms that make up Earth and its inhabitants were formed within stars. Stars form in the
dusty spiral arms of galaxies and spend their lives changing hydrogen and helium to heavier
elements. As they die, some stars eject these elements into space by cataclysmic explosions. The
sun and the planets, including Earth, probably condensed from a cloud of dust and gas enriched by
the recycled remnants of exploded stars. Earth formed by the accretion of cold particles about 4.6
billion years ago. Heat from debris and radioactive decay partially melted the planet, and density
stratification occurred as heavy materials sank to its center and lighter materials migrated toward the
surface. The ocean formed later, as water vapor trapped in Earth’s outer layers escaped to the
surface through volcanic activity during the planet’s youth. Life originated in the ocean very soon after
its formation. We know of no other planet with a similar ocean, but water is abundant in interstellar
clouds and other water planets are not impossible to imagine.
In the next chapter you will learn that science and exploration have gone hand in hand. Voyaging
for necessity evolved into voyaging for scientific and geographical discovery. The transition to
scientific oceanography was complete when the Challenger Report was completed in 1895. The rise
of the great oceanographic institution quickly followed, and those institutions and their funding
agencies today mark our path into the future.