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S6E3: Recognize the significant role of water on
earth processes.
E.Q.: What are characteristics of oceans, and why
are oceans important?
Composition and Structure of
Earth’s Oceans
 Why are oceans salty?
 What does the seafloor look like?
 How do temperature, salinity, and density affect ocean
structure?
Salinity
 The “saltiness” or
dissolved content of a
body of water.
Seawater
 Water from the sea or
ocean.
 Has an average salinity of
3.5 %
 If you had a 1000 grams
of seawater, 35 grams of
it would be salts and the
rest pure water
brackish
 Freshwater mixed with
seawater.
 Lagoons
Abyssal plain
 Large, flat areas of the
seafloor that extend
across the deepest parts
of the ocean basins.
Earth’s Oceans
 The Pacific Ocean-Largest and deepest ocean. Larger
than all of Earth’s combined land areas.
 The Atlantic Ocean-half the size of the Pacific.
Occupies about 20% of Earth’s surface.
 The Indian Ocean-Between Africa, India, and the
Indonesian Islands. Third largest ocean.
Earth’s Oceans
 The Southern Ocean-Surrounds Anarctica. The
fourth largest ocean. Ice covers some its surface all
year.
 The Arctic Ocean-Near the North Pole. Smallest and
shallowest Ocean. Ice covers some of its surface all
year.
Formation of the Oceans
 The Earth’s oceans began to form around 4.2 billion
years ago.
 Ancient volcanic eruptions added water vapor and
other gases to the atmosphere.
 As early Earth cooled, the water vapor condensed and
rain fell for tens of thousands of years, collecting in
basin that became oceans.
Formation of the Oceans
 Asteroids and comets were a second source of water
for Earth’s oceans. The melted ice from these objects
added to the water filling the Earth’s ocean basin.
 As tectonic plates move, new oceans form and old
oceans disappear. The volume of oceans has remained
fairly constant since oceans first formed.
Composition of Seawater
 The rain that fell to Earth’s surface billions of years ago
washed over rocks and dissolved minerals.
 The minerals contained substances that formed salts.
 Rivers and streams carried these substances to the
ocean basins which made the oceans salty.
Composition of Seawater
The Seafloor
 What does the seafloor look like?
 Continental Margins-Part of an ocean basin next to a
continent. Extends from shoreline to the deep ocean.
Divided into continental shelf (shallow),
continental slope (steep), and the continental rise
(at the base of the slope).
The Seafloor
 Abyssal plains-large flat areas of the seafloor that
extend across the deepest parts of the ocean basin.
 Thick layers of sediment
 Some underwater volcanoes.
The Seafloor
 Mid-ocean Ridges-Places on the seafloor where
tectonic plates pull apart and volcanic mountains
form.
 Ocean trenches-areas where an oceanic tectonic plate
collides with a continental plate and forms a deep
canyon or trench. Trenches are the deepest parts of
the ocean.
The Seafloor
 Scientist use submersibles and other technologies to
explore the seafloor.
 The seafloor contains valuable resources. Two main
categories of resources are energy and minerals.
 Energy resources-oil, natural gas, and methane.
 Mineral resources-manganese, gold, and zinc.
Zones in the Ocean
 Oceans are divided into regions or zones based on
characteristics that include amount of sunlight,
temperature, salinity, and density.
 Surface zone-shallow area of seawater that gets the
most sunlight.
 Middle zone-Receives only faint blue-green light.
 Deep zone-No light. Plants do not grow. Some
animals make their own light.
Zones in the Ocean
 Amount of sunlight
Ocean Layers
 Temperature, salinity, and density vary with depth.
 Sometimes these characteristics can change quickly
within a short change in depth which creates
distinctive layers of seawater.
Lesson 2: Ocean Waves and
Tides
 Essential Questions:
 What causes ocean waves?
 What cause tides?
tsunami
 A wave that forms when
an ocean disturbance
suddenly moves a large
volume of water.
 In other words, a really
big wave caused by
earthquake, landslide, or
volcanic eruption.
Sea level
 The average level of the
ocean’s surface at any
given time.
tide
 Periodic rise and
fall of the ocean’s
surface caused by
the gravitational
force between the
Earth and Moon,
and between the
Earth and Sun.
Tidal range
 The difference
in water level
between a high
tide and a low
tide.
Spring tide
 Has the largest tidal
range and occurs when
Earth, the Moon, and the
Sun form a straightline.
Neap tide
 Has the lowest tidal
range and occurs when
Earth, the Moon, and the
Sun form a right angle.
Parts of a Wave
 Crest-the highest part of a wave.
 Trough-the lowest part of a wave.
 Wavelength-the distance from crest to crest.
Surface Waves
 Wind causes these waves to roll onto a beach.
 Range in size from tiny ripples to huge waves several
meters high.
 Three factors affect size of surface waves. Wind speed,
time, and distance.
Wave Motion
 Waves transport water particles in a circular pattern.
 As depth increases, the circular motion decreases.
 At the wave base, wave motion stops.
 Wave base is equal to ½ the wavelength of the wave
above.
Wave Motion
When Surface Waves Reach
Shore
 As a wave moves into shallow water, it changes shape
and size.
 As the base of the wave drags on the seafloor, its speed
decreases, the wavelength shortens, and the height
increases.
 When the wave gets too high for the wave base to
support the crest, it collapses, or breaks.
Tsunamis
 Tsunamis have a short wave height.
 Usually less than 30 cm high, but the wavelength can
be hundreds of kilometers long.
 Water from a tsunami just keeps coming and can cause
much damage.
 A 2004 tsunami in the Indian Ocean killed more than
225,000 people in 11 countries and destroyed entire
villages.
 http://video.nationalgeographic.com/video/101videos/tsunami-101
Tides
 The gravitational force between the Moon and Earth
causes tides.
 The largest tides occur in an area when the Moon is
directly facing the area or directly opposite
 Coastlines, shape and size of the ocean basin, and
depth of the ocean affect tide.
Tides
 The Moon is full or new during a spring tide.
 High and low tides occur during neap tides and spring
tides, however the range between high and low tides is
less during a neap tide.
Lesson 3: Ocean Currents
 Essential Questions
 What are the major types of ocean current?
 How do ocean currents affect weather and climate?
Ocean Current
 A large volume of water
flowing in a certain
direction
Gyre
 A circular
system of
currents.
Coriolis effect
 The movement of wind
and water to the right or
left that is caused by
Earths’ rotation
Upwelling
 The vertical
movement of
water toward
the ocean’s
surface.
Major Ocean Currents
 Surface Currents-form when wind blows over water
and the moving air particles drag on the surface and
cause the water to move.
 A gyre is a circular system of surface currents.
 Gyre move in different directions because of the
Coriolis Effect.
Major Ocean Currents
 Surface Currents-form when wind blows over water
and the moving air particles drag on the surface and
cause the water to move.
 A gyre is a circular system of surface currents.
 Gyre move in different directions because of the
Coriolis Effect.
Major Ocean Currents
 Surface currents move water horizontally across the
ocean’s surface, but upwelling currents move water
vertically toward the ocean’s surface.
 Density currents move cold water from the ocean
surface to deeper parts of the ocean.
Impacts on Weather and Climate
 A system of surface currents and density currents that
distributes thermal energy around Earth.
 The Gulf Stream is a warm-water current.
 The California Current is a cold-water current.
Impacts on Weather and Climate
Impacts on Weather and Climate
 The Great Ocean
Conveyor Belt slowly
moves water around
the globe.
 Warm surface
currents and cold
density currents
interacting to
distribute thermal
energy.
Lesson 4: Environmental Impacts
on Oceans
 How does pollution affect marine organisms?
 How does global climate change affect marine
ecosystems?
 Why is it important to keep oceans healthy?
marine
 Refers to
anything
related to the
ocean.
Harmful algal blooms
 An
explosive
growth of
algae that
harms
organisms.
Coral bleaching
 Loss of color in corals
that occurs when
stressed corals expel
the algae that live in
them.
Ocean Pollution
 Sources of pollution
 Runoff from land
 Airborne pollutants that
start over land.
 Spill from shipping
 Dumping trash
 Offshore mining and
drilling for resources.
Effects of Ocean Pollution
 Cause problems for
marine organisms.
 Excess nitrates cause
algae blooms that can
kill fish that eat them.
 Excess sediments can
clog filtering structures
of filter feeders and
block light so that
photosynthesizing
organisms die.
 Some algae blooms use
up all the oxygen in the
water and fish can’t get
the oxygen they need.
Oceans and Global Climate
Change
Effects of increasing
temperature
Effects of increasing
carbon dioxide
 Choral bleaching
 CO2 combines with seawater
 Glaciers and ice sheets melt
adding more water to the
oceans, raising sea level.
to create Carbonic Acid
which lowers the pH level of
the water.
 This causes the ocean to
 The warmer the water, the
less O2 and organisms die.
become more acidic.
 Acidity can cause shells and
skeletons of organisms to
weaken or dissolve.
Keeping Oceans Healthy
 Earth’s oceans stabilize Earth systems and provide
many resources to humans.
 It’s important to keep oceans healthy because they
distribute moisture and thermal energy.
 Marine algae produce oxygen for our atmosphere.
 Oceans provide resources for humans and habitat for
marine organisms.