Chapter 18 Ocean
Motion
Section 18-1 Ocean Water Notes
Guide
Water Distrubution
Importance of Oceans
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Oceans are important sources of food, energy,
and minerals.
-Energy sources such as oil, and natural gas are
found beneath the ocean floor.
- Copper and gold are mineral resources that
are mined in shallow waters.
- One-third of the world’s table salt is extracted
from seawater by the process of evaporation.
-Millions of tons of oil, coal, and grains are
shipped over the oceans each year.
Origin of the Oceans
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When the Earth was young, its surface was
much more volcanically active than it is today.
When volcanoes erupt they give off lava, ash,
water vapor, carbon dioxide, and other gases.
The water vapor was stored in Earth’s
atmosphere, until it cooled enough to condense
and into storm clouds.
Rains begin to fall, and the water filled low areas
on the Earth called basins.
70 % of Earth’s surface is covered by ocean
water.
Origin of Oceans
Composition of the Oceans
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Ocean water contains dissolved gases such as
oxygen, carbon dioxide, and nitrogen.
-Oxygen is needed by organisms for respiration.
-Oxygen enters the oceans from the atmosphere
and from organisms that photosynthesize.
-Carbon dioxide enters the ocean from the
atmosphere and from organisms when they
respire.
-Nitrogen comes from the atmosphere.
Composition of the Oceans
Continued…
 Ocean
water contains many dissolves
salts.
-Chloride and sodium are some of the ions
in seawater.
-These ions come from rocks that are
dissolved slowly by rivers and
groundwater and are carried to the ocean.
-Erupting volcanoes add other ions.
 Many other ions are dissolved in seawater.
Composition of Oceans
Continued…
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When seawater evaporates, the ions combine to form
salts.
-Sodium and chloride ions combine to form
halite, which gives the ocean it’s salty taste.
Salinity is the measure of amount of salts
dissolved in seawater.
It is measures in grams of dissolved salts per kilogram of
seawater.
One kilogram of seawater contains 35 g of dissolved salts or
3.5 percent.
This proportion has stayed constant for hundreds of millions of
years.
Composition of Oceans
Removal of Elements
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The ocean is in a steady state-elements are added to the
oceans at the same rate that they are removed.
Dissolved salts precipitate out of ocean water and
become part of the sediment.
Marine organisms use dissolved salts to make body
parts.
- Some remove calcium from the water to make bones.
- Some use dissolved calcium to form shells, like
oysters.
-Calcium and silicon are removed more quickly from
seawater than other elements.
Desalination
 Salt
can be removed from ocean water by
the process of desalination.
 As water evaporates, salt is left behind.
 Scientists are working on technology to
remove salt from seawater to make it
drinkable.
 Desalination plants use several methods
to remove salt from the seawater to obtain
freshwater for drinking.
Desalination