Earth Science 14.1 The Vast World Ocean
The Vast World Ocean
The Blue Planet
The World’s Oceans:
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Nearly 71% of the Earth’s
surface is covered by ocean.
Yet to this day we probably
know more about the solar
system than we do about what
life exists at the very bottom
of our oceans.
Not until the late 1800s did we
even start to examine our
oceans in detail and try to
understand the complex web of
life that can be found there.
The Blue Planet
The World’s Oceans:
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New technologies in recent
years have allowed scientists
to collect much data about the
world’s oceans.
As technology has advanced,
the field of oceanography has
grown.
Oceanography, the study of
the world’s oceans, is a science
that draws on the methods and
knowledge of geology,
chemistry, physics, and biology
to study all aspects of the
world’s oceans.
The Blue Planet
The World’s Oceans:
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The total area of the Earth’s
surface is about 510 million
square kilometers.
Of this, about 360 million square
kilometers (71%) is covered with
oceans or smaller seas such as
the Mediterranean Sea.
The remaining Earth’ surface,
150 million square kilometers
(29%) is covered by the
continents and islands.
The world’s oceans can be
divided into 4 main ocean basins:
The Pacific Ocean, the Atlantic
Ocean, the Indian ocean, and the
Arctic ocean.
The Blue Planet
The World’s Oceans:
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The Pacific Ocean is the
largest of Earth’s oceans.
It is the single largest
geographical feature on the
Earth’s surface.
It covers more than half the
ocean surface on Earth.
It is also the world’s deepest
ocean with an average depth of
3940 meters.
The Blue Planet
The World’s Oceans:
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The Atlantic Ocean is about
half the size of the Pacific
Ocean.
It is a relatively narrow ocean
compared to the Pacific.
Both the Atlantic and Pacific
are bounded to the east and
west by continents.
The Blue Planet
The World’s Oceans:
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The Indian Ocean is slightly
smaller than the Atlantic
Ocean, but is about the same
average depth.
Unlike the Atlantic and Pacific,
the Indian ocean is located
almost entirely in the southern
hemisphere.
The Blue Planet
The World’s Oceans:
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The Arctic Ocean is about 7%
of the size of the pacific
ocean.
It is only a little more than one
quarter as deep as the rest of
the oceans.
The Blue Planet
Topography of the Oceans:
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If all the water were drained
from the ocean basins, a
variety of features would be
seen.
These features include chains
of volcanoes, tall mountain
ranges, deep ocean trenches,
and large submarine plateaus.
The topography of the ocean
floor is as diverse as that of
the continents.
The Blue Planet
Topography of the Oceans:
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An understanding of oceanfloor features came with the
development of techniques to
measure the depth of the
oceans.
Bathymetry is the
measurement of ocean depths
and the charting of the shape
or topography of the ocean
floor.
The Blue Planet
Topography of the Oceans:
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The first understanding of the
ocean floors varied topography
did not occur until the historic 3
and a half year voyage of the
HMS Challenger.
From December 1872 to May
1876, the HMS Challenger
expedition made the first, and
perhaps most comprehensive,
study of the global ocean ever
attempted by a group.
Throughout the voyage, they
measured water depth by
lowering long weighted lines
overboard. Today, scientists use
modern techniques such as
SONAR to accomplish the same
tasks.
Route of the HMS Challenger,
it covered over 1000 days and
68,000 nautical miles
The Blue Planet
SONAR:
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In the 1920’s, a technological
breakthrough occurred with
the invention of sonar, a type
of depth sounding equipment.
Sonar is an acronym for Sound
Navigation And Ranging.
The Blue Planet
SONAR:
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Sonar, also referred to as echo
sounding, works by
transmitting sound waves
towards the ocean bottom.
A receiver than detects the
signals that bounce back from
the ocean bottom and
determines the depth by
calculating the speed of sound
waves in water (about 1500
meters per second) .
The Blue Planet
SONAR:
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The depths determined from
continuous plotting of these
signals allows scientists to plot
the ocean floor to reveal
features such as plateaus and
mountain ranges.
In the last few decades, more
complex systems using multibeam sonar systems have
developed. These multi-beam
systems gather information on a
strip of ocean floor rather than
a single point by using multiple
beams simultaneously.
By towing behind a ship, like
mowing a lawn, oceanographers
can build up a map of an area in a
shorter time span.
The Blue Planet
Satellite Measurement:
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Measuring the shape of the ocean
floor from space is another recent
technological breakthrough that has
led to a better understanding.
After compensating for waves,
tides, currents, and atmospheric
affects; scientists have discovered
that the ocean surface is not
perfectly flat.
This is because gravity attracts
water toward regions where massive
ocean floor features occur.
Therefore, mountain ranges and
ridges produce elevated areas on
the ocean’s surface that can be
measured from space. Canyons and
trenches cause slight depressions.
The Blue Planet
Satellite Measurement:
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The difference in ocean height
is not visible to the naked eye
however satellites are able to
measure these small
differences by bouncing
microwaves off the ocean
surface.
By knowing the satellite’s
exact position through GPS,
sea-surface height can be
measured to a tolerance of 3
to 6 centimeters.
The data from these type of
measurements can be used to
build detailed ocean maps in a
much faster amount of time.
The Blue Planet
Submersibles:
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Another way scientists learn
about the ocean floor is by
direct contact; going there in
small submarines designed to
handle the immense pressures
of deep ocean waters.
A submersible is a small
underwater craft used for
deep-sea research.
The Blue Planet
Submersibles:
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Submersibles are used to
collect data about areas of the
ocean that were previously
unreachable.
Submersibles are equipped
with a number of instruments
and recording devices to
capture all types of
information, from temperature
and pressure gauges to video
and audio recording tools.
The Blue Planet
Submersibles:
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The first submersible was used
in 1934 by William Beebe. He
descended to a depth of 923
meters off Bermuda in a steel
sphere that was tethered to a
mother ship.
In 1960, Jacques Piccard
descended in the untethered
submersible Trieste to 10,912
meters below the ocean
surface into the Mariannas
Trench.
The Blue Planet
Submersibles:
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Alvin and Sea Cliff II are two
modern day manned
submersibles used for deep sea
research.
Alvin can reach a depth of
4000 meters and Sea Cliff II
can reach 6000.
The Blue Planet
Submersibles:
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Today many submersibles are
unmanned and operated
remotely. The are call ROVs
for remotely operated
vehicles.
They collect data, record
video, and have robot arms
that can be used to dig,
retrieve objects, and work
underwater at great depths.
Computer Lab Assignment
Use the internet to research and create a short mini-report
on one of the following topics.
 Sonar mapping of the ocean floor
 Satellite mapping of the ocean floor
 Submersibles and their use in exploration of deep
ocean areas.
 You must write at least 3 paragraphs or create 3
PowerPoint slides on your chosen topic. YOU MAY NOT
CUT,COPY OR PASTE. PUT IT IN YOUR OWN
WORDS