Download Earth`s Oceans Power Point

The World’s Oceans
 71%
of the Earth’s surface is covered
by ocean water.
 The oceans contain 97% of the
earth’s water.
 All the oceans and seas are actually
one continuous body of water.
Oceans
 The
oceans are the Atlantic, Pacific,
Indian. Arctic and Southern.
 The Pacific Ocean is the largest
ocean.
 The area and volume of the Pacific
Ocean are greater than the Atlantic
and Indian combined.
Seas
A
sea is a part of an ocean that is
nearly surrounded by water.
 The Mediterranean, Arctic and Black
Sea are really part of the Atlantic
Ocean.
Water Cycle




The sun’s rays heat
the surface of the
ocean.
The heat causes the
water to evaporate.
The evaporating water
(clean, fresh water)
enters the atmosphere
as water vapor.
The salt remains
behind.
Water Cycle
Winds carry water
vapor over land.
 Some of the water
vapor condenses to
form clouds.
 The water in the
clouds falls as
precipitation.

Water Cycle
Some of this water
runs into rivers
and streams which
flow back into the
oceans.
 Some of the water
seeps into the soil
and rocks become
part of the
groundwater.

Properties of Ocean Water
 Ocean
water is a mixture of gases
and solids dissolved in pure water.
 Oceanographers believe oceans
contain all the natural elements on
Earth.
 85 of 90 have been found in the
ocean.
Major Elements in the Ocean
 Ocean
water is 96% pure water.
 Chlorine (1.9) and sodium (1.1)
make up the next largest
concentration of elements.
 Sodium chloride is table salt.
Salinity
 Salinity
describes the amount of
dissolved water in the ocean.
 Salinity is expressed in parts per
thousand.
 The salinity level of the ocean is
expressed in parts per thousand.
 The average salinity of ocean is 35
parts per thousand.
Sources of Salt in the Ocean
 When
volcanoes erupt, rock
materials and gases, such as
chlorine, spew forth.
 As rivers, streams and glaciers move
over rock and soil, they dissolve
salts, such as magnesium, sodium
and potassium, in them.
 As waves pound the shoreline, they
dissolve salts from the rocks.
Salinity Levels


The salinity is lower in areas where freshwater
rivers run into the ocean. Salinity levels are also
affected by animals such as clams and oysters
that use calcium salts to build their shells. They
remove salt from the water.
In warm ocean areas where there is little rainfall
and much evaporation, the amount of dissolved
salts is much greater. In polar regions, the
salinity levels are high because temperatures are
cold enough for ocean water to freeze. Pure
water is removed and salts are left behind.
Gases in Ocean Water
 The
most abundant gases in ocean
water are nitrogen, carbon dioxide
and oxygen.
 The amounts of these elements vary
with depth. They are more abundant
at the ocean’s surface where sunlight
causes more plant life.
Temperature of Ocean Water
 Warm
water holds less dissolved gas
than cold water.
 When ocean water is cold, like in
polar regions, it sinks and carries
oxygen rich water to the ocean
depths.
 As a result, fish and other animals
can live in deep parts of the ocean.
Temperature of Ocean Water
Sun is the major
source of heat for
the ocean.
 Motions of the
ocean, such as
waves and
currents, mix the
surface water and
transfer the heat
downward.

Surface Zone
The zone where the water is mixed by
waves and currents is called the surface
zone.
 The surface zone extends 100-400 meters
downward.
 The temperature remains constant with
depth.
 Temperature in a surface zone changes
due to seasons and locations.

Thermocline
The zone of rapid temperature change is
called the thermocline.
 The thermocline does not occur at a
certain depth.
 The season and flow of ocean currents
alter the depth of the thermocline.
 The thermocline exists because warm,
surface water does not mix easily with
colder, denser water.

Deep Zone
 The
thermocline forms a transition
between the surface zone and the
deep zone.
 The deep zone is an area of
extremely cold water that extends
from the bottom of the thermocline
to depths of 4000 meters or more.
Deep Zone
 Within
the deep zone, temperatures
decrease only slightly.
 At depths greater than 1500 meters,
the temperature is about 4 degrees
C.
 The three ocean zones are not found
in the polar (Arctic and Antarctica)
regions since the surface waters are
always cold.
The Ocean Floor

The topography of the ocean floor is
different from the topography of the
continents
The Ocean Floor
The ocean floor has higher mountains,
deeper canyons, and larger flatter plains.
Earthquakes occur more often.
 The rocks are very different.
 The crust is thinner.

Edges of the Continents
The shoreline is a boundary between
where the land and the ocean meet.
 The area where the underwater edge
meets of a continent meets the ocean
floor is called a continental margin.

Continental Margin
 The
area where the underwater edge
of a continent meets the ocean floor
is called a continental margin.
 A continental margin consists of a
continental shelf, a continental slope
and a continental rise.
Continental Shelf
 The
flat part of a continental margin
that is covered by shallow ocean
water is called a continental shelf.
 A continental shelf slopes gently
from the shoreline.
 The width of the continental shelf
varies.
 Large mineral, oil and natural gas
deposits are found here.
Continental Slope
 At
the edge of the continental shelf,
the ocean floor plunges steeply 4 to
5 kilometers.
 A continental slope marks the
boundary between the crust of the
continent and the crust of the ocean
floor.
Continental Rise
 Separating
a continental slope from
the ocean floor is a continental rise.
 A continental rise is made of large
amount of sediments, rocks, plants
and animals.
 Sometimes the sediments are carried
down the slope in masses of flowing
water called turbidity currents, like
an underwater avalanche.
Submarine Canyons
 In
many areas, submarine canyons
cut through a continental shelf and
slope.
 They are deep, V-shaped valleys that
have been cut in the rock, possibly
by turbidity currents.
 The Monterey Submarine
Canyon(2000 meters) is deeper than
the Grand Canyon.
Abyssal Plains
 Large,
flat areas on the ocean floor
are called abyssal plains.
 The abyssal plains are larger in the
Atlantic and Indian than in the Pacific
due to the deposition of sediments
by large rivers.
 The Pacific Ocean has large cracks
that trap sediments and result in
smaller abyssal plains.
Abyssal Plains
 Abyssal
plains close to the continent
are made of mud, sand and silt.
 Farther out on the abyssal plains,
some of them contain the remains of
tiny organisms that form ooze.
 Where ocean life is not abundant,
the floor of the ocean is covered with
red clay
Seamounts and Guyots
Seamounts are underwater volcanic
mountains that rise more than 100 meters
above the ocean floor. Most have been
found in the Pacific Ocean.
 Some seamounts reach above the surface
of the water to form islands, like the
Azores in the Atlantic and the Hawaiian
islands in the Pacific.
 Guyots are flat-topped seamounts.

Trenches
 Trenches
are the deepest parts of the
ocean found along the edge of the
ocean floor.
 The Mariana Trench in the Pacific
Ocean contains the deepest spot
(1100 meters) on Earth known as
Challenger Deep.
Midocean Ridges
 The
midocean ridges form an almost
continuous mountain belt that
extends from the Arctic Ocean down
through the middle of the Atlantic
Ocean around Africa into the Indian
Ocean and across the Pacific Ocean.
 In the Atlantic it is called the midAtlantic Ridge and in the Pacific, the
Pacific-Antarctica Ridge.
Formation of Midocean Ridges
 Mountain
ranges on land are formed
when the Earth’s crust folds and is
squeezed together.
 Midocean ridges are areas where
molten material from deep within the
Earth flows up to the surface and
cools and forms new crust.
Rifts
 Running
along the middle of the
midocean ridges between the rows of
parallel mountains are deep crevices
or rifts.
 Rifts are areas of great earthquake
and volcanic activity.
Reefs
 Surrounding
volcanic islands in
tropical waters are large masses and
ridges of limestone rock, known as
coral reefs.
 The limestone structures contain the
shells of animals. These animals
cannot exist in water cooler than 18
degrees C and deeper than 55
meters.
Types of Coral Reefs
 Fringing
reefs
 Barrier reefs
 Atoll
Fringing Reefs
 Fringing
reefs are coral reefs that
touch the shoreline of a volcanic
island.
 Fringing reefs are usually less than
30 meters.
Barrier Reefs
 Barrier
reefs are separated from the
shore by an area of shallow water
called a lagoon.
 Barrier reefs are usually larger than
fringing reefs and surround islands
that are more submerged.
 The largest barrier reef is the Great
Barrier Reef of Australia. It is 23oo
km long and 320 km wide.
Atoll
 An
atoll is a ring of coral reefs that
that surround an island that has sunk
beneath the surface of the ocean.
Ocean Life Zones
 Intertidal
Zone (Splash Zone)
 Neritic Zone (Continental Shelf)
 Open Sea Zone –
 Bathyal (Continental Slope)
 Abyssal (Ocean floor)
Ocean Life Zones
 The
plant and animal life in the
ocean is affected by several factors.
 One factor is the amount of sunlight
that penetrates the ocean.
 Another factor is the temperature of
the ocean water.
 Water pressure is also a factor.
Major Groups of Ocean Life
 Plants
and animals in the ocean are
classified into three major groups
based on their habits and the depth
of the water in which they live.
 The three major groups are
plankton, nekton and benthos.
Plankton
 Plankton
float at or near the surface
where sunlight can penetrate.
 Most of the plankton are very small,
such as algae.
 These organisms drift with the
currents or tides.
 Plankton are the main food for many
larger organisms. They account for
most of the organisms in the ocean.
Nekton
 Whales
, seals , dolphins, squid
octopuses, barracuda and other fish
are all nekton.
 Nekton are free-swimming organisms
that feed on other nekton as well as
on plankton.
 Many have adaptations enabling
them to function at depths that have
great pressure and no light.
Benthos
 Organisms
that live on the ocean
floor are benthos.
 The forms of these animals include
crustaceans and shell fish.
 The deep bottom environments are
sparsely populated with benthos.
 Some benthos are plants that live on
the ocean floor in shallow waters
where sun can penetrate.
Ocean Life Zones
 The
classification of the ocean into
life zones is based on the conditions
in the ocean. These conditions vary
widely.
 The classification includes the
intertidal zone, the neritic zone and
open-ocean zones.
Intertidal (Splash) Zone
 This
region is the most changeable in
the ocean.
 Anemones, crabs, clams, mussels
and plants such as seaweed live
here.
 They must be able to exist without
water for periods of time.
 They must be able to anchor to keep
from being washed out to sea.
Neritic ( Shelf) Zone
 This
zone extends to a depth of 200
meters and receives plenty of
sunlight.
 The water pressure is low and the
temperature is constant.
 This zone can support plankton,
nekton and benthos.
 Marine life is most abundant here.
Open Ocean Zones
 There
are two open-ocean
zones:bathyal and abyssal
Bathyal (Slope)
 The
bathyal zone begins at the
continental slope and extends down
about 2000 meters.
 Sunlight cannot penetrate the
bottom of this zone and plants do
not grow at the bottom.
 Many forms of nekton, such as squid,
octopus and large whales live in this
zone.
Abyssal (Ocean Floor) Zone
At a depth of about 2000 meters, the
abyssal zone begins.
 The abyssal zone extends to a depth of
6000 meters.
 This zone covers the large flat plains of
the ocean. No sunlight can penetrate and
food is scarce. The water pressure is
great.
 Most of the animals here are small.
 Some make their own light.

Studying the Ocean Floor
In 1872, the first expedition to explore the
ocean began when the Challenger sailed
from England.
 Scientists used wire to measure the ocean
depth.
 Scientists aboard used nets to collect
animals and plants from the ocean floor.
 Special thermometers measured the
temperature. Samples of water were
collected.

Present Oceanographers
 Today
oceanographers have modern
instruments.
 Underwater cameras provide pictures
of the ocean floor. Corers bring up
samples of med and sand from the
ocean bottom.
 Bathyspheres, bathscaphs and other
submersibles are able to dive deep
under the surface to explore
Mapping the Ocean Floor
 One
of the most important goals is to
map the ocean floor. This is done by
indirect methods such as echo
sounding, radar, sonar and
seismographic surveys.
Echo Soundings
All of these methods are based on the
same principles. Energy waves are sent
down to the floor are reflected and return
to the surface, where they are recorded.
 Knowing the speed of sound, 1500 m per
second, oceanographers can determine
the depth.
 The most complete picture was gathered
from information from a satellite, the
Seasat, launched in 1978

Motions of the Oceans
 Ocean
water never stops moving.
 The three basic motions of the ocean
are : the up and down movement of
the waves. The steady movement of
ocean currents and the rise and fall
of the ocean tides.
Waves
 Waves
are pulses of energy that
move through the ocean.
 Waves are set in motion by winds,
earthquakes and the gravitational
pull of the moon.
 The most common source of wave
movement is the wind blowing across
the surface.
Movement of Waves
The water in a wave is not moving forward
at all. Only the energy moves forward
through the water producing one wave
after another.
 The energy is passed from particle to
particle. It is also passed downward.
With increasing depth, the motion of the
particles decrease. At a certain depth the
motion stops. In deep water, there are no
waves except those caused by tides and
earthquakes.

Height of the Waves
 Three
factors affect the height of
waves: wind speed, the length of
time the wind blows and the distance
the wind blows over the water.
 As
each of these factors increases,
the height of the wave increases.
Wave Characteristics
The point of the wave is called the crest.
 The lowest point of the wave is called the
trough.
 The horizontal distance between two
consecutive crests or troughs is the
wavelength.
 The vertical distance between a crest and
a trough is called the wave height.

Wave Period and Frequency
 The
amount of time it takes
consecutive crests or troughs to pass
is called the wave period.
 The number of crests or troughs
passing a given point in a certain
wave period is called the wave
frequency.
 As wave frequency increases, wave
length decreases.
Swells
 Waves
stay the same distant apart
out in the open ocean. The
wavelength is constant. These
waves are called swells.
Surf
 Waves
change as they near the
shore. They slow down and get
closer together. Their wavelength
decreases and their increase until
they crash forward as breakers. This
is called the surf.
Undertow
 The
water then flows back toward
the ocean carrying bits of seaweeed,
sand and pebbles. The retreating
water is called an undertow.
Tsunamis
 Some
ocean waves are caused by
earthquakes.
 Tsunamis have very long
wavelengths and are very deep.
 They carry a huge amount of energy
Which is concentrated in much less
water as it nears the shore.
 Tsunamis reach heights of 35 meters
(an average 10-story building).
Currents
 Water
below the surface moves in
streams called currents.
 Currents are caused by two factors:
wind patterns and differences in
water density.
Surface Currents
 Currents
caused mainly by wind
patterns are called surface currents.
These currents have a depth of
several hundred meters.
 The temperature of a current
depends on where it originated,
making it either warm or cold.
Long-Distance Currents
 Surface
currents that travel
thousands of kilometers are called
long-distance currents, such as the
Gulf Steam.
 The Gulf Stream carries warm water
from the southern tip of Florida north
along the eastern coast of the United
States moving at speeds of 1.5
meters per second.
Continuous Currents
 All
currents form a continuous
worldwide pattern of water
circulation.
 The water in each ocean moves in a
large, almost circular pattern.
 In the Northern Hemisphere, the
currents move clockwise.
 In the Southern hemisphere, the
currents move counterclockwise.
Short- Distance Currents
Short distance currents are usually found
near a shoreline where the waves hit at an
angle.
 When the waves hit the shoreline, the
water turns and produces currents that
move parallel to the shoreline called
longshore currents. Longshore currents
move large quantities of sand which
deposit in sand bars.

Rip Current
 If
the longshore current cuts an
opening in the sandbar the water will
return to ocean in a powerful narrow
flow called a rip current.
 A rip current is a type of undertow.
Deep Currents
 Deep
currents are caused mainly by
differences in water density.
 The cold, salty water, that is more
dense, flowing from the polar regions
moves under the less dense water
away from the polar regions.
 Most deep currents flow in the
opposite direction from surface
currents.
Upwellings
The densest water on Earth lies off the
coast of Antarctica.
 This water sinks to the ocean floor and
flows north. As the Antarctic currents
come close to land, the ocean floor rises,
forcing these cold currents upward.
 These risings, called upwellings, carry rich
food from the ocean floor that results in
rich fishing grounds near PSpring and

Neap Tides
 Spring Tides, higher than normal