Exploring the Ocean
• Since ancient times
people have studied the
ocean such as waters
and ocean floor
• It provides food and
services, and serves as a
route for trade and
travel
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.
Ocean Floor Makeup
• 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 topography of the ocean floor is different
from the topography of the continents
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 area of the ocean
floor that extends outward from the
edge of a continents is called a
continental shelf.
Continental shelf
• Depth of 130 meters and gets steeper
• 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
Continental Slope
• The steep edge of the continental
shelf
• 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.
Abyssal Plain
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
Plates
• Pieces of earths crust along with parts of the upper
mantle are called plates.
• The plates move at an average speed of several
centimeters per year-barely faster than your
fingernails grow
• This is what
shaped the dramatic
features of the ocean,
such as mountains
and trenches
Seafloor Spreading
• Mid ocean ridge is along
boundaries of plates that are
moving apart or Diverging
adding a new strip of rock to
the ocean floor
• Magma squeezes up through
cracks
• Magma hardens
• Seafloor spreading is what
produced our ocean floor
• When plates come together
or Converge, one plate sinks
under the other
Mid Ocean Ridge
Mid ocean Ridges
• The mid ocean 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 ,
much as the line of stitches winds around a
baseball.
• In the Atlantic it is called the mid-Atlantic
Ridge and in the Pacific, the Pacific-Antarctica
Ridge.
Formation of Mid ocean Ridges
• Mountain ranges on land are formed when
the Earth’s crust folds and is squeezed
together.
• Mid ocean ridges are areas where molten
material from deep within the Earth flows up
to the surface and cools and forms new crust.
• Has 2 parallel chains of mountains separated
by valley and trenches
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.
Rifts
• Running along the middle of the mid ocean
ridges between the rows of parallel mountains
are deep crevices or rifts.
• Rifts are areas of great earthquake and
volcanic activity.
Trenches
• Trenches are the
deepest parts of the
ocean found along the
edge of the ocean floor.
• Is a steep sided canyon
in the ocean floor
• The Mariana Trench in
the Pacific Ocean
contains the deepest
spot on Earth- the
Challenger Deep.
Mariana Trench
• The Mariana Trench is 2, 542 km (1,580 miles) long
(more than five times the length of the Grand
Canyon) and 69 km (43 miles) wide
• The Challenger Deep is 11,033 meters (36,201
feet), almost 7 miles
• If Mount Everest, which is the tallest point on Earth
at 8,850 meters (29,035 feet), were set in the
Mariana Trench, there would still be 2,183 meters
(7,166 feet or about 2 miles) of water left above it.
• http://deepseachallenge.com/the-expedition/mariana-trench/
• https://www.youtube.com/watch?v=9FYKLS7xjpg
Mariana
Trench
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 elements 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 salt
in the ocean.
• Salinity is expressed in parts per thousand.
• The average salinity of the 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 in them, such as
magnesium, sodium and potassium.
• As waves pound the shoreline, they dissolve
salts from the rocks.
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.
• 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.
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.
Ocean Life Zones
• Intertidal Zone (Splash Zone)
• Neritic Zone (Continental Shelf)
Open Sea Zones
• Bathyal Zone (Continental Slope)
• Abyssal Zone (Ocean floor)
Ocean Life Zones
• The plant and animal life in the ocean is
affected by several factors.
– the amount of sunlight that penetrates the
ocean.
– the temperature of the ocean water.
– Water pressure
• 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.
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.
– Plankton
– Nekton
– 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, octopus, barracuda
and other fish are all
nekton.
• Nekton are freeswimming organisms that
feed on other nekton as
well as 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.
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.
Estuary
• An environment along
the oceans edge
• Is a coastal inlet or bay
where fresh water from
a river mixes with salty
ocean water.
• Water is known as
brackish.
Coastal Wetlands
• Are habitats found in
and around estuaries
• Along the US coasts,
most wetlands are
either mangrove
forests or salt
marshes.
Salt Marshes
 Have muddy soil that is
rich in nutrients and
dominant plant is cord
grass
 Tide channels running
through the grass break
up waves, thus
protecting organisms
from the ocean surf
Mangroves
 Have arching prop roots
that anchor the trees to
the land
 Roots break up wind and
waves protecting
organisms that live there
 Roots also trap sediment
so water is rich in
nutrients
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.
Coral Reefs
• Can form only in
shallow tropical ocean
waters
• Produce a hard
material around their
soft bodies
• When they die, the
hard material is left
behind
Kelp Forests
• Grow in cold neritic
waters where the
ocean has a rocky
floor
Open Ocean Zones
• There are two open-ocean zones: Bathyal & 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.
• Many deep sea fishes
produce their own light
called bioluminescence.
Hydrothermal Vent
• Located in the deep
zone
• Is an area in which
heated ocean water
rises through the
cracks of ocean floor
• Chemical nutrients
in the heated water
support unique
organisms.
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 mud
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
Sonar
• Stands for Sound
Navigation and
Ranging
• Is a system that uses
sound waves to
calculate the
distance to an object