Chapter 13
Exploring the Oceans
I. Earth’s Oceans
A. Global Ocean
• Contains most of the water that covers 71% of
the Earth
• Divided by the continents into five main oceans
1. Pacific Ocean
- Largest ocean
- Flows between Asia and the Americas
2. Atlantic Ocean
- Second largest ocean; half the volume of the
Pacific
- Flows between the Americas and Africa
3. Indian Ocean
4. Southern Ocean
- Extends from the coast of Antarctica to 60°
south latitude
5. Arctic Ocean
- Smallest ocean
- Much of its surface is covered by ice
B. How Did the Oceans Form?
• 4.5 billion years ago, there were no oceans
• Volcanoes spewed lava, ash, and gases
• Volcanic gases formed Earth’s atmosphere and
caused temperatures to decrease by blocking the
sun
• Earth cooled enough for water vapor to condense
and fall as rain
• When all the landmasses were collected into
Pangia, the surrounding ocean was called
Panthalassa
• As Pangaea broke apart, the North Atlantic and
Indian Ocean began to form
C. Characteristics of Ocean Water
1. Salty
• Sodium chloride (NaCl) – same salt you
flavor food with
2. Salinity
• The amount of dissolved solids in a given
amount of liquid
• Places with hotter, drier climates typically
have a higher salinity because heat increases
the evaporation rate
• Places with cooler, more humid climates
typically have a lower salinity
• Slow-moving areas of water develop high
salinity
3. Temperature Zones
• Temperature decreases as
depth increases
• Water can be divided into three
zones
a. Surface Zone
- warm, top layer
- Can extend to 300m below
sea level
- Sunlight heats the top 100m
and surface currents mix the
heated water with cooler
water below
b. Thermocline
- Can extend from 300m to about 700m below
sea level
- Temperature drops faster with increased
depth than it does in the other two zones
c. Deep Zone
- Extends from the bottom of the thermocline
to the bottom of the ocean
- Temps range from 1°C to 3°C
D. The Water Cycle
• A continuous movement of water from the
ocean to the atmosphere to the land and
back to the ocean
1. Evaporation
- Sun heats liquid water, causing it to rise into
the atmosphere as water vapor
2. Condensation
- Water vapor in the atmosphere cools and
interacts with dust particles
- Water vapor eventually turns to liquid water
3. Precipitation
• Water droplets eventually become heavy
enough and fall back to Earth’s surface as
precipitation
E. A Global Thermostat
• Water has a high specific heat
- It takes a lot of energy to raise the
temperature of a large body of water by 1°C
- It also has to release a lot of energy for the
temperature to drop
• Dry land has a low specific heat
- Land can change temperature quicker than
water because it does not require as much
energy
• Air temperature remains steady due to the
thermal energy between the ocean and the
atmosphere
• The air temperature would change drastically if
land made up a larger percentage of Earth’s
cover (>30%)
II. The Ocean Floor
A. Studying the Ocean Floor
• Sending people to the ocean floor can be
risky so other method’s of surveying it from
above water are needed
1. Seeing by Sonar
- Sonar stands for Sound Navigation
And Ranging
- Sound pulses from a ship are sent
down into the ocean
- The sound moves through the
water, bounces off the ocean
floor, and returns to the ship
- The deeper the water is, the
longer the round trip
- The travel time is divided by two
and then multiplied by the speed
of sound (1,500 m/s)
2. Oceanography via Satellite
- Seasat allowed scientists to measure the
direction and speed of ocean currents
-Geosat measures slight changes in the height
of the ocean’s surface
B. Revealing the Ocean Floor
1. Regions of the Ocean Floor
a. Continental Margin
• Made of continental crust
• Consists of the continental shelf, the
continental slope, and continental rise
i. Continental Shelf
- Begins at the shoreline and slopes gently
toward the open ocean
ii. Continental slope
- Begins at the edge of the continental shelf
and continues down to the flattest part of the
ocean floor
iii. Continental Rise
- The boundary between the continental margin
and the deep-ocean basin lies underneath the
continental rise
b. Deep-ocean basin
- Made of oceanic crust
- Consists of the abyssal plain, mid-ocean
ridges, rift valleys, and ocean trenches
- Most of these features form near the
boundaries of Earth’s tectonic plates
i. Abyssal Plain
- The broad, flat part of the deep-ocean basin
ii. Mid-ocean Ridges
- Mountain chains that form where tectonic
plates pull apart and magma rises to fill in the
rift zones
iii. Rift Valley
- Forms between mountains in the rift zone
iv. Ocean Trenches
- Form where one oceanic plate is pushed
beneath a continental plate or another
oceanic plate
C. Exploring the Ocean with Underwater Vessels
• Some vessels contain the air that explorers
need to breathe and all the equipment they
need to study the ocean
• Exploring the deep ocean by using piloted
vessels is expensive and can be very dangerous
due to the extreme pressure
• Robotic vessels are designed to withstand
pressures much greater than those found in
the deepest parts of the ocean and are “flown”
by a pilot at the surface
III. Life in the Ocean
A. The Three Groups of Marine Life
1. Plankton
• Organisms that float or drift freely near the
ocean’s surface
• Most are microscopic
a. Phytoplankton - plantlike
b. Zooplankton - animal like
2. Nekton
• Organisms that swim
actively in the open
ocean
• Include mammals as
well as many varieties
of fish
3. Benthos
• Organisms that live on
or in the ocean floor
B. The Benthic Environment “Bottom
Environment”
1. The Intertidal Zone
• Shallowest benthic zone
• Located between the high-tide and low-tide
limits
2. The Sublittoral Zone
• Starts at the low-tide limit and ends at the edge
of the continental shelf
• The temperature, water pressure, and amount
of sunlight remain fairly constant
• The kind of sediment on the ocean floor
influences where organisms live in the
sublittoral zone
3. The Bathyal Zone
• Extends from the edge of the continental
shelf to the abyssal plain
• Plant life is scarce because of the lack of
sunlight
4. The Abyssal Zone
• Largest ecological zone of the ocean
• No plants and very few animals live in the
abyssal zone
• Many of these organisms live around hot-water
vents called blacksmokers
5. The Hadal Zone
• Deepest zone that consists of the floor of the
ocean trenches
C. The Pelagic Environment
• The zones near the ocean’s surface and at the
middle depths
1. The Neritic Zone
• Covers the continental shelf
• Warm, shallow zone
• Contains the largest concentration of marine
life
2. The Oceanic Zone
• Covers the entire sea floor except for the
continental shelf
• The water temperature is cooler and the
pressure is greater
• Organisms are more spread
IV. Resources from the Ocean
A. Living Resources
1. Fishing the Ocean
• Almost 75 million tons of fish are harvested
each year
• Overfishing reduces fish populations
• People have begun to raise ocean fish in fish
farms to help meet the demand
B. Nonliving Resources
1. Oil and Natural Gas
• Found under layers of
impermeable rock
• Petroleum engineers
must drill through this
rock in order to reach
these resources
• Seismic equipment is
used to indicate how rock
layers are arranged below
the ocean floor and
which layers contain oil
2. Fresh Water and Desalination
• Desalination is the process of removing salt
from sea water
• Found in drier parts of the world such as
Saudi Arabia and Kuwait
3. Sea-Floor Minerals
• Nodules of manganese, iron, copper, nickel,
and cobalt are found on the ocean floor
4. Tidal Energy
• Generated from the
movement of tides
a. As the tide rises, water enters
a bay behind a dam
b. The gate of the dam closes at
high tide
c. The tide lowers
d. At low tide, the gate opens
and the water behind the dam
rushes out, moving through
turbines, which in turn,
generates electrical energy
V. Ocean Pollution
A. Nonpoint-Source Pollution
• Pollution that comes from many sources
rather than just from a single site
• Human activities on land can pollute
streams and rivers, which then flow into the
ocean and bring the pollutants they carry
with them
B. Point-Source Pollution
• Pollution that comes from a specific site
1. Trash Dumping
- Dumping trash in the deeper parts of the
ocean
- Trash thrown into the ocean can affect the
organisms that live in the ocean and those
organisms that depend on the ocean for food
2. Sludge Dumping
- Raw sewage, or the liquid and solid wastes
that are flushed down toilets and poured
down drains
- Settles on the ocean floor but can be stirred
by currents and moved closer to shore
3. Oil Spills
• Large tankers that transport billions of barrels
of oil across the oceans can be disastrous
• Oil spills can harm plants, animals, and
people
C. Saving Our Ocean Resources
• A treaty was passed 64 countries in 1989 that
prohibits the dumping of certain metals,
plastics, oil, and radioactive wastes
• The U.S. has passed an act that prohibits the
dumping of any material that would affect
human health or welfare, the marine
environment or ecosystems, or business that
depend on the ocean