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Chapter 13: Exploring the Oceans
Our Ocean
 About 71% of the Earth’s
surface is covered with water.
Where is all that water found?
In the ocean, of course!
 Just look at a map…most of it
is blue, which represents our
oceans.
 The four major oceans are the
Atlantic, Pacific, Arctic, and
Indian.
 Since there are no defined
boundaries, we usually just
refer to the ocean as the
“world ocean” because they
are all connected.
How Did the Ocean Form?
 We need to go back millions of years ago when the Earth
first formed. It was very hot and volcanically active.
 As we have learned, there are lots of gases contained
within the lava in volcanoes, so when there are eruptions,
these gases are released.
 Water vapor is one of the most common gases found in lava,
and this helped to form a young atmosphere.
 As more and more water vapor was added to the
atmosphere, clouds formed, and precipitation fell for many
millions of years.
 Over time, our oceans filled up!
What is Ocean Water Like?
 Have you ever been to the
beach, gotten smacked in the
face by a wave, and ended up
with a mouthful of salt water?
Yuck!
 The ocean has lots of elements
dissolved in it, but the two in
greatest abundance are sodium
(Na) and chlorine (Cl). That
makes NaCl…table salt!
 Where do these elements come
from? The rivers dissolve the
minerals of the continents and
dump them into the ocean.
Saltiness
 The saltiness of the ocean is called its salinity. This
is defined by the amount of dissolved solids in a
given amount of liquid.
 The unit of measurement for salinity is parts per
thousand (ppt). In other words, grams of solids per
kilograms of water.
 The average salinity of the ocean is 35 ppt.
What Affects Salinity?
 Many factors can change the saltiness of
ocean water.
1. Evaporation: water is being removed, leaving the
salts behind (higher salinity).
2. Freshwater input: during precipitation and at
deltas, lots of fresh water is added (lower
salinity).
3. Freezing: just like evaporation, water freezing is
just that…only water! The salts are left behind
(higher salinity).
4. Confined space: if a body of water is enclosed by
land like the Mediterranean Sea the salinity will
increase.
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Ocean Temperature
As you travel deeper into the ocean, the temperature
decreases dramatically.
Why? There is no sunlight in the deep ocean to heat the water!
Three temperature zones:
1. Surface (sea level down to 300 m): temperature varies
depending on sunlight
2. Thermocline (300 m-700 m): has a rapid decrease in
temperature with depth
3. Deep (700 m-bottom): is pretty much always cold no matter
what
Temperature, cont’d
 Water is unique because once it absorbs solar radiation from
the Sun, it holds on to it for a long time.
 This helps to regulate the temperatures in the atmosphere. The
ocean will warm or cool the air above it, therefore allowing
coastal cities to be warmer or cooler than inland cities.
 Ocean currents distribute the warmer waters to colder regions
and colder waters to warmer regions.
 The heat budget in the ocean and atmosphere is balanced!
The Immense Ocean Floor
 Part of the continents is underwater along our
coastlines. This partially submerged outer extension
of the continental crust is called the margin.
 The two types of margins are active (near plate
boundaries) and passive (NOT near plate boundaries)
 Margins are divided into regions:
1.
2.
3.
4.
5.
6.
Passive are
found in the
Atlantic and
active are in the
Pacific
Shelf
Shelf break
Slope
Rise (only in passive)
Abyssal plain
Trench (only in active)